Proposed methods report for the Roper catchment - updated Australia’s National Science Agency A report from the CSIRO Roper River Water Resource Assessment for the National Water Grid Authority ISBN 978-1-4863-1399-0 (print) ISBN 978-1-4863-1400-3 (online) Citation CSIRO (2021) Proposed methods report for the Roper Catchment - updated. A report from the CSIRO Roper River Water Resource Assessment for the National Water Grid Authority. CSIRO, Australia. Copyright © Commonwealth Scientific and Industrial Research Organisation 2021. To the extent permitted by law, all rights are reserved and no part of this publication covered by copyright may be reproduced or copied in any form or by any means except with the written permission of CSIRO. Important disclaimer CSIRO advises that the information contained in this publication comprises general statements based on scientific research. The reader is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or actions must therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the extent permitted by law, CSIRO (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this publication (in part or in whole) and any information or material contained in it. CSIRO is committed to providing web accessible content wherever possible. If you are having difficulties with accessing this document please contact Email CSIRO Enquiries . CSIRO Roper River Water Resource Assessment acknowledgements This report was funded through the National Water Grid Authority’s Science Program, which sits within the Australian Government’s Department of Climate Change, Energy, the Environment and Water. Aspects of the Assessment will be undertaken in conjunction with the Northern Territory Government. The Assessment will be guided by two committees: i. The Assessment’s Governance Committee: CRC for Northern Australia/James Cook University; CSIRO; National Water Grid Authority (Department of Climate Change, Energy, the Environment and Water); NT Department of Environment, Parks and Water Security; NT Department of Industry, Tourism and Trade; Office of Northern Australia; Qld Department of Agriculture and Fisheries; Qld Department of Regional Development, Manufacturing and Water ii. The Assessment’s joint Roper and Victoria River catchments Steering Committee: Amateur Fishermen’s Association of the NT; Austrade; Centrefarm; CSIRO, National Water Grid Authority (Department of Climate Change, Energy, the Environment and Water); Northern Land Council; NT Cattlemen’s Association; NT Department of Environment, Parks Australia; Parks and Water Security; NT Department of Industry, Tourism and Trade; Regional Development Australia; NT Farmers; NT Seafood Council; Office of Northern Australia; Roper Gulf Regional Council Shire Responsibility for the Assessment’s content lies with CSIRO. The Assessment’s committees will not have an opportunity to review the Assessment results or outputs prior to its release. Dr Mila Bristow reviewed an earlier version of the Proposed Methods Report. This version has been updated with groundwater hydrology methods and change of milestone dates. Acknowledgement of Country CSIRO acknowledges the Traditional Owners of the lands, seas and waters, of the area that we live and work on across Australia. We acknowledge their continuing connection to their culture and pay our respects to their Elders past and present. Photo Fieldwork, Roper catchment. Source: CSIRO Director’s foreword Sustainable regional development is a priority for the Australian and Northern Territory governments. Across northern Australia, however, there is a scarcity of scientific information on land and water resources to complement local information held by Indigenous owners and landholders. Sustainable regional development requires knowledge of the scale, nature, location and distribution of the likely environmental, social and economic opportunities and the risks of any proposed development. Especially where resource use is contested, this knowledge informs the consultation and planning that underpins the resource security required to unlock investment. In 2019 the Australian Government commissioned CSIRO to complete the Roper River Water Resource Assessment. In response, CSIRO accessed expertise and collaborations from across Australia to provide data and insight to support consideration of the use of land and water resources for development in the Roper catchment. While the Assessment focuses mainly on the potential for agriculture, the detailed information provided on land and water resources, their potential uses and the impacts of those uses are relevant to a wider range of regional-scale planning considerations by Indigenous owners, landholders, citizens, investors, local government, the Northern Territory and federal governments. Importantly the Assessment will not recommend one development over another, nor assume any particular development pathway. It provides a range of possibilities and the information required to interpret them - including risks that may attend any opportunities - consistent with regional values and aspirations. All data and reports produced by the Assessment will be publicly available. C:\Users\bru119\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Word\C_Chilcott_high.jpg Chris Chilcott Project Director The Roper River Water Resource Assessment Team Project Director Chris Chilcott Project Leaders Cuan Petheram, Ian Watson Project Support Caroline Bruce Communications Chanel Koeleman/Kate Cranney, Siobhan Duffy, Amy Edwards Activities Agriculture and socio- economics Chris Stokes, Caroline Bruce, Shokhrukh Jalilov, Diane Jarvis1, Adam Liedloff, Yvette Oliver, Alex Peachey2, Allan Peake, Maxine Piggott, Perry Poulton, Di Prestwidge, Thomas Vanderbyl7, Tony Webster, Steve Yeates Ecology Danial Stratford, Laura Blaney, Rik Buckworth, Pascal Castellazzi, Bayley Costin, Roy Aijun Deng, Ruan Gannon, Sophie Gilbey, Rob Kenyon, Darran King, Keller Kopf3, Stacey Kopf3, Simon Linke, Heather McGinness, Linda Merrin, Colton Perna3, Eva Plaganyi, Rocio Ponce Reyes, Jodie Pritchard, Nathan Waltham9 Groundwater hydrology Andrew R. Taylor, Karen Barry, Russell Crosbie, Phil Davies, Alec Deslandes, Katelyn Dooley, Clement Duvert8, Geoff Hodgson, Lindsay Hutley8, Anthony Knapton4, Sebastien Lamontagne, Steven Tickell5, Sarah Marshall, Axel Suckow, Chris Turnadge Indigenous water values, rights, interests and development goals Pethie Lyons, Marcus Barber, Peta Braedon, Kristina Fisher, Petina Pert Land suitability Ian Watson, Jenet Austin, Elisabeth Bui, Bart Edmeades5, John Gallant, Linda Gregory, Jason Hill5, Seonaid Philip, Ross Searle, Uta Stockmann, Mark Thomas, Francis Wait5, Peter L. Wilson, Peter R. Wilson Surface water hydrology Justin Hughes, Shaun Kim, Steve Marvanek, David McJannet, Catherine Ticehurst, Biao Wang Surface water storage Cuan Petheram, Fred Baynes6, Kevin Devlin7, Arthur Read, Lee Rogers, Lynn Seo, Ang Yang, Note: Assessment team as at June 15, 2023. All contributors are affiliated with CSIRO unless indicated otherwise. Activity Leaders are underlined. 1James Cook University; 2NT Department of Industry, Tourism and Trade; 3 Research Institute for the Environment and Livelihoods. College of Engineering, IT & Environment. Charles Darwin University; 4CloudGMS; 5NT Department of Environment, Parks and Water Security; 6Baynes Geologic; 7independent consultant; 8Charles Darwin University9Centre for Tropical Water and Aquatic Ecosystem Research. James Cook University. Shortened forms For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au Units For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au Preface Sustainable regional development is a priority for the Australian and Northern Territory governments. For example, in 2023 the Northern Territory Government committed to the implementation of a new Territory Water Plan. One of the priority actions announced by the government was the acceleration of the existing water science program ‘to support best practice water resource management and sustainable development’. The efficient use of Australia’s natural resources by food producers and processors requires a good understanding of soil, water and energy resources so they can be managed sustainably. Finely tuned strategic planning will be required to ensure that investment and government expenditure on development are soundly targeted and designed. Northern Australia presents a globally unique opportunity (a greenfield development opportunity in a first-world country) to strategically consider and plan development. Northern Australia also contains ecological and cultural assets of high value and decisions about development will need to be made within that context. Good information is critical to these decisions. Most of northern Australia’s land and water resources, however, have not been mapped in sufficient detail to provide for reliable resource allocation, mitigate investment or environmental risks, or build policy settings that can support decisions. Better data are required to inform decisions on private investment and government expenditure, to account for intersections between existing and potential resource users, and to ensure that net development benefits are maximised. In consultation with the Northern Territory Government, the Australian Government prioritised the catchment of the Roper River for investigation (Preface Figure 1-1) and establishment of baseline information on soil, water and the environment. Northern Australia is defined as the part of Australia north of the Tropic of Capricorn. The Murray– Darling Basin and major irrigation areas and major dams (greater than 500 GL capacity) in Australia are shown for context. The Roper River Water Resource Assessment (the Assessment) will provide a comprehensive and integrated evaluation of the feasibility, economic viability and sustainability of water and agricultural development. While agricultural developments are the primary focus of the Assessment, it will also consider opportunities for and intersections between other types of water-dependent development. For example, the Assessment will explore the nature, scale, location and impacts of developments relating to industrial and urban development and aquaculture, in relevant locations. The Assessment is designed to inform consideration of development, not to enable any particular development to occur. As such, the Assessment will inform – but not seek to replace – existing planning, regulatory or approval processes. Importantly, the Assessment does not assume a given policy or regulatory environment. As policy and regulations can change, this will enable the results to be applied to the widest range of uses for the longest possible time frame. Preface Figure 1-1 Map of Australia showing Assessment area It was not the intention – and nor will it be possible – for the Assessment to generate new information on all topics related to water and irrigation development in northern Australia. Topics not directly examined in the Assessment are discussed with reference to and in the context of the existing literature. Functionally, the Assessment will adopt an activities-based approach (reflected in the content and structure of the outputs and products), comprising seven activity groups; each will contribute its part to create a cohesive picture of regional development opportunities, costs and benefits. Preface Figure 1-2 illustrates the high-level links between the seven activities and the general flow of information in the Assessment. Preface Figure 1-2 Schematic diagram of the high-level linkages between the 7 activities and the general flow of information in the Assessment. Assessment reporting structure Development opportunities and their impacts are frequently highly interdependent and consequently, so is the research undertaken through this Assessment. While each report may be read as a stand-alone document, the suite of reports will most reliably inform discussion and decisions concerning regional development when read as a whole. The Assessment will produce a series of cascading reports and information products: • Technical reports; that present scientific work at a level of detail sufficient for technical and scientific experts to reproduce the work. Each of the seven activities (outlined below) will have one or more corresponding technical report. • A Catchment report; that for the Roper catchment synthesises key material from the technical reports, providing well-informed (but not necessarily-scientifically trained) readers with the information required to make decisions about the opportunities, costs and benefits associated with irrigated agriculture and other development options. • A Summary report; that for the Roper catchment provides a summary and narrative for a general public audience in plain English. • A Summary factsheet; that for the Roper catchment provides key findings for a general public audience in the shortest possible format. The Assessment will also develop online information products to enable the reader to better access information that is not readily available in a static form. All of these reports, information tools and data products will be available online at https://www.csiro.au/roperriver. The website will provide readers with a communications suite including factsheets, multimedia content, FAQs, reports and links to other related sites, particularly about other research in northern Australia. For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au Executive summary The Roper River Water Resource Assessment will provide a comprehensive and integrated evaluation of the feasibility, economic viability and sustainability of water resource development in the Roper catchment (Northern Territory). The Assessment seeks to: • evaluate the climate, soil and water resources • identify and evaluate water capture and storage options • identify and test the commercial viability of irrigated agricultural, forestry and aquaculture opportunities • assess potential environmental, social and economic impacts and risks of water resource and irrigation development. In addition, the Assessment is designed to: • address explicitly the needs and aspirations of local development • meet the information needs of governments as they assess sustainable and equitable management of public resources, with due consideration of environmental and cultural issues • meet the due diligence requirements of private investors, by exploring questions of profitability and income reliability of agricultural and other developments. The objective of this report is to broadly outline the methods proposed for the Assessment. The purpose is to openly communicate the scope of the Assessment and the proposed methods to a wide range of stakeholders, to allow them to provide feedback and engage with the Assessment team. The report also provides a mechanism for the Assessment team to acquire feedback on the proposed methods, to ensure that they are fit for purpose. The actual methods that the Assessment will use may differ as more information becomes available and local nuances are better understood. The final methods will be documented in technical detail in the final technical reports. The Assessment comprises the following interrelated activities, which are discussed below. Availability of water The availability of surface water across the Roper catchment will primarily be assessed using three types of hydrological models: (i) a conceptual rainfall-runoff model (Sacramento), (ii) river system model, and (iii) hydrodynamic model (MIKE FLOOD) (see surface water hydrology activity, Chapter 3). The conceptual rainfall-runoff model will be used to quantify water fluxes across the Roper catchment. These fluxes will be used as inputs to the river system and hydrodynamic models. River system models are well suited to modelling regulated systems, and exploring how streamflow may be perturbed under future development, management and climate scenarios. The river system modelling provides an integrating framework for analysing the opportunities by which surface water development may enable regional development. Hydrodynamic models are physically based models that explicitly model the movement of water across the landscape. These models will be used to examine how large and small flood events, and the connectivity of offstream wetlands and the main river channel, are affected by future development and climate scenarios. Interim digital land suitability maps (Chapter 4), potential dam locations (Chapter 6) and key ecological assets (Chapter 8) will inform the structure of the river system model. The latter will inform the domain of the hydrodynamic model. The groundwater hydrology activity (Chapter 10) seeks to provide a comprehensive assessment of the most promising intermediate to regional- scale aquifers in the Roper catchment, in the context of identifying opportunities for, and risks associated with, groundwater resource development to enable regional development. The groundwater activity will conduct a combination of desktop, field and modelling investigations based on the current level of existing information for different aquifers across the catchment. Investigations will likely target the Tindall Limestone Aquifer and its equivalents as well as the Dook Creek Formation and its equivalents. Investigations will comprise: (i) assessing the important hydrogeological attributes (i.e. spatial extent, saturated thickness, water quality, bore yield, aquifer properties) that identify aquifers as suitable for future development, (ii) characterise the scale and residence time of key groundwater flow processes, and the degree of inter-aquifer connectivity and groundwater – surface water connectivity of key aquifers, (iii) estimate groundwater recharge and discharge across the catchment and (iv) evaluate the quantity of potential available groundwater for future development and identify the potential risks of groundwater extraction on known groundwater-dependent ecosystems. One of the challenges of working in northern Australia is the scarcity of data and the remoteness of the landscape. For these reasons, the Assessment will seek to use remotely sensed imagery (i.e. satellite imagery) where it can meaningfully inform the information needs of the Assessment. This will include use of the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua satellites, and archival multi-temporal Landsat imagery from the Australian Geoscience Data Cube. The work will involve mapping flood inundation (to help constrain the hydrodynamic modelling), identifying persistent waterholes (key ecological refuge Chapter 8). Availability of suitable soil The land suitability activity (Chapter 4) will develop digital land suitability maps of the entire Roper catchment, showing areas that are more and less suitable under different combinations of land use and irrigation systems, and aquaculture. The activity will employ statistically based digital soil mapping methods to rapidly and objectively generate 90 m × 90 m, or finer grids of a wide range of soil attributes (e.g. depth of soil, texture, pH). The digital soil mapping will be informed by a limited soil sampling campaign. The current set of rules for different combinations of land use and irrigation systems, and aquaculture will be refined. The rules will be applied to the digital soil mapping attributes, and landscape and climate raster data to generate land suitability maps of the catchment. Indigenous aspirations and water values The Indigenous values, rights, interests and development goals (Chapter 5) will provide an overview of key Indigenous values, rights, interests and aspirations with respect to water and irrigated agricultural development in the Roper catchment. This analysis is intended to assist, inform and underpin future discussions between developers and Indigenous people about particular developments, and their potential positive and negative effects on Indigenous populations. The activity will closely align with components of the agriculture and socio-economics activity (Chapter 7) and the ecology activity (Chapter 8). The fieldwork component of this activity will emphasise direct consultation with Traditional Owners of, and residents in, the Assessment area. This will be undertaken through a variety of means, including telephone discussions, face-to- face interviews, group meetings and workshops. Other key components of the activity include a cultural heritage assessment, and a legal and policy analysis. Surface water storage options The surface water storage activity (Chapter 6) will provide a comprehensive overview of the different surface water storage options in the Roper catchment, to help decision makers take a long-term view of water resource development and to inform future allocation decisions. The construction of inappropriate storages and incremental releases of water can preclude the development of more appropriate water storages and water development options. The work will include a pre-feasibility assessment of large instream and offstream dams. The activity will also include a study of large on-farm (e.g. 2 to 8 GL) hillside dams and ringtanks. The river system models (Chapter 3) will be used to explore how the reliability of harvesting water into ringtanks decreases with increasing catchment allocation and extraction, and other factors such as pumping capacity and the threshold above which water can be taken. Digital soil maps (Chapter 4) will be used to provide information on areas that are suitable for on-farm storage, such as ringtanks. Agriculture viability and socio-economics The agriculture and socio-economics activity (Chapter 7) will fully integrate biophysical agriculture production with an economic assessment. The activity will include crop and forage modelling and analysis using the Agricultural Production Systems sIMulator (APSIM), the Grass Production Model (GRASP), and expert knowledge and experience. Some limited field studies may be undertaken as part of this activity to assist in validating crop and forage models and estimates of crop and forage production. Although the agricultural and socio-economics activity will analyse individual crops and forages to help provide fundamental information on potential yields, water use, growing seasons and gross margins, for example, the aim is not to be prescriptive about cropping systems for particular locations; rather, the aim is to provide insights into the issues and opportunities associated with developing integrated cropping or crop–livestock systems, as opposed to individual crops. This activity will extend the economic analysis to the scheme scale, using industry standard cost– benefit analysis methods. The impact of an irrigation development on the regional economy of the Roper catchment will be estimated using regional economic multipliers, following the approach used in the Northern Australia Water Resource Assessment. Information on the possible locations and scale of water resource development will be provided by the surface water hydrology (Chapter 3), land suitability (Chapter 4) and surface water storage (Chapter 6) activities. Freshwater, riparian and near-short marine ecology The ecology activity (Chapter 8) seeks to assess the potential for possible changes in flow regimes associated with new infrastructure across the Assessment area to affect aquatic ecosystems including freshwater and freshwater dependent marine ecosystems. The Assessment focuses on water-related ecosystems because water developments, particularly irrigation, can result in substantial changes to streamflow, although typically water developments occupy only a small proportion of the landscape (<1% of a catchment). Key tasks in the ecology activity will include identifying and prioritising assets in the Assessment area, for which conceptual models that capture flow–ecology relationships will be developed. A multiple lines of evidence approach will be used to develop relationships between flow and ecology. These will be qualitative where information is poor and semi-quantitative or quantitative where information is sufficient. The activity will use hydrological outputs from the surface water hydrology modelling (Chapter 3) to which the flow–ecology relationships will be applied to identify likely ecological changes to freshwater and marine ecosystems as a result of different types and scales of water resource development. Case study experiments The Assessment will also undertake a small number of case studies in the Roper catchment (Chapter 9). Their purpose is to show the reader how to ‘put everything together’ to answer their own questions about water resource development. As well, they aim to help readers understand the types and scales of opportunities for irrigated agriculture in selected geographic parts of the Assessment area, and explore some of the nuances associated with greenfield developments in the catchments, and northern Australia in general. Importantly, they are not designed to demonstrate, recommend or promote particular development opportunities being proposed by individual development proponents, nor are they recommendations on how development in the Roper catchment should unfold. They are, however, designed to be realistic representations, and will explore a variety of potential water resource development options and scales of development. The case studies will draw on information, expertise and models from all activities in the Assessment. Contents Director’s foreword .......................................................................................................................... i The Roper River Water Resource Assessment Team ...................................................................... ii Shortened forms .............................................................................................................................iii Units ............................................................................................................................... iv Preface ............................................................................................................................... v Executive summary ....................................................................................................................... viii Part I 1 1 Introduction ........................................................................................................................ 2 1.1 Roper River Water Resource Assessment ............................................................. 2 1.2 Reporting schedule ................................................................................................ 4 1.3 Review process ...................................................................................................... 5 1.4 Past studies and links to relevant current projects ............................................... 5 1.5 Objectives and contents of this report .................................................................. 6 1.6 References ............................................................................................................. 8 2 Key concepts ....................................................................................................................... 9 2.1 Water year, and wet and dry seasons ................................................................... 9 2.2 Scenario definitions ............................................................................................... 9 2.3 Case studies ......................................................................................................... 10 2.4 References ........................................................................................................... 10 Part II 13 3 Surface water hydrology ................................................................................................... 14 3.1 Introduction ......................................................................................................... 14 3.2 Model overview ................................................................................................... 14 3.3 Data availability ................................................................................................... 16 3.4 Model calibration and modelling experiments ................................................... 17 3.5 References ........................................................................................................... 19 4 Land suitability .................................................................................................................. 21 4.1 Introduction ......................................................................................................... 21 4.2 Workflow ............................................................................................................. 22 4.3 References ........................................................................................................... 27 5 Groundwater hydrology ................................................................................................... 29 5.1 Regional geology and hydrogeology of the Roper catchment ............................ 29 5.2 Regional hydrogeological desktop assessment ................................................... 32 5.3 Hydrogeological Framework ............................................................................... 33 5.4 Groundwater recharge and flow ......................................................................... 36 5.5 Groundwater discharge ....................................................................................... 41 5.6 Assessing the opportunities and risk for future groundwater development ..... 43 5.7 References ........................................................................................................... 43 Part III 49 6 Indigenous water values, rights, interests and development goals ................................. 50 6.1 Introduction ......................................................................................................... 50 6.2 Linkages to other Assessment activities .............................................................. 51 6.3 Linkages to other research projects in the Roper catchment ............................. 51 6.4 Context and consultation .................................................................................... 51 6.5 Scope ................................................................................................................... 52 6.6 Research ethics .................................................................................................... 52 6.7 Methods .............................................................................................................. 53 6.8 Data analysis and preliminary dissemination ...................................................... 54 6.9 Staff and collaboration ........................................................................................ 55 6.10 Project governance and oversight ....................................................................... 55 6.11 References ........................................................................................................... 55 7 Surface water storage ....................................................................................................... 57 7.1 Introduction ......................................................................................................... 57 7.2 Large instream and offstream storages .............................................................. 58 7.3 Farm-scale instream and offstream storages ...................................................... 60 7.4 References ........................................................................................................... 62 8 Agriculture and socio-economics ..................................................................................... 63 8.1 Farm-scale analyses ............................................................................................. 64 8.2 Scheme-scale analyses ........................................................................................ 66 8.3 Regional economic impacts ................................................................................. 67 8.4 References ........................................................................................................... 67 Part IV 71 9 Ecology ............................................................................................................................. 72 9.1 Regional overview ............................................................................................... 72 9.2 Ecology activity breakdown ................................................................................. 73 9.3 References ........................................................................................................... 76 Part V 79 10 Case studies ...................................................................................................................... 80 10.1 Rationale .............................................................................................................. 80 10.2 Proposed case study framings ............................................................................. 80 10.3 References ........................................................................................................... 81 11 Reports, products, protocols and standards .................................................................... 82 11.1 Reports, products and protocols ......................................................................... 82 11.2 Standards ............................................................................................................. 82 Figures Preface Figure 1-1 Map of Australia showing Assessment area ..................................................... vi Preface Figure 1-2 Schematic diagram of the high-level linkages between the 7 activities and the general flow of information in the Assessment. ............................................................................ vii Figure 1-1 The Roper catchment in the Northern Territory ........................................................... 6 Figure 1-2 Schematic diagram illustrating the high-level linkages between the seven activities and general flow of information in the Assessment ....................................................................... 8 Figure 3-1 Roper catchment showing stream gauge locations and maximum flood extent (MODIS) ......................................................................................................................................... 17 Figure 4-1 Land suitability analysis workflow, key inputs and processes (Thomas et al., 2018a) 22 Figure 4-2 Collecting soil cores in the field using a vehicle-mounted push core rig. The collected soil will be analysed in the field and a subset subjected to laboratory analysis .......................... 23 Figure 4-3 Soil sample being extracted from coring tube in the field .......................................... 24 Figure 5-1 Regional hydrogeology of the Roper catchment ......................................................... 32 Figure 8-1 Overview of the approach for assessing the agricultural and economic viability of agricultural development options in the Roper catchment ......................................................... 64 Tables Table 1-1 Key deliverables for the Assessment .............................................................................. 4 Table 4-1 Land suitability classes based on FAO (1976) and adapted from DSITI and DNRM (2015) and van Gool et al. (2005) ................................................................................................. 26 Table 7-1 Proposed methods for assessing potential dam sites in the Roper catchment ........... 59 Table 7-2 Types of offstream water storages (Lewis, 2002) ......................................................... 61 Part I Introduction and overview 1 Introduction 1.1 Roper River Water Resource Assessment The Roper River Water Resource Assessment will provide a comprehensive and integrated evaluation of the feasibility, economic viability and sustainability of water resource development in the Roper catchment (Northern Territory). The Assessment seeks to: •evaluate the climate, soil and water resources •identify and evaluate water capture and storage options •identify and test the commercial viability of irrigated agricultural, forestry and aquacultureopportunities •assess potential environmental, social and economic impacts and risks of water resource andirrigation development. It is important to note that, although these four points appear in sequence, activities in one part of the Assessment will often inform (and hence influence) activities in an earlier part. For example, understanding ecological requirements (the third part of the Assessment, described in Part IV of this report) is particularly important in setting rules around water extraction and diversion (i.e. how much water can be taken and when it should be taken – the second part of the Assessment, described in Part III of this report). Thus, the procedure of assessing a site will inevitably include iterative steps, rather than a simple linear process. In covering the above points, the Assessment is designed to: •address explicitly the needs and aspirations of local development by providing objectiveassessment of resource availability, with consideration of the environmental and cultural issues •meet the information needs of governments as they assess sustainable and equitablemanagement of public resources, with due consideration of environmental and cultural issues •meet the due diligence requirements of private investors, by exploring questions of profitabilityand income reliability of agricultural and other developments. Drawing on the resources of all three tiers of government, the Assessment will build on previous studies, draw on existing stores of local knowledge, and employ world-class scientific expertise, with the quality of the studies assured through peer-review processes. The Roper River Water Resource Assessment commenced on 1 July 2019 and will be completed by 1 December 2023. 1.1.1 Scope of Assessments In stating what the Assessment will do, it is equally instructive to state what they will not do. The Assessment will not advocate irrigation development. It will identify the resources that could be deployed in support of irrigation and aquaculture enterprises, and the scale of the opportunity that might exist. They are designed to evaluate the feasibility of development (at a catchment scale), not to enable particular developments. The Assessment will quantify the monetary and non-monetary values associated with existing use of resources, to enable a wide range of stakeholders to assess the likely costs and benefits of given courses of action. The Assessment is fundamentally a resource assessment, the results of which can be used to inform planning decisions by citizens; councils; investors; and the state, territory and Australian governments. The Assessment does not seek to replace any planning processes, and they will not recommend changes to existing plans or planning processes. The Assessment will not invest or promote investment in infrastructure that may be required to support irrigation enterprises. It seeks to lower barriers to investment in the Assessment area by exploring many of the questions that potential investors might have about production systems and methods, yield expectations and benchmarks, and potential profitability and reliability. This information will be established for the Assessment area, not for individual paddocks or farms. The Assessment does not assume that particular areas within the Assessment areas are in or out of scope. For example, the Assessment is ‘blind’ to issues such as land tenure that may exclude land parcels from development. The Assessment will identify those areas that are best suited for new agricultural and aquaculture developments and industries, and, by inference, those that are not well suited. The Assessment does not assume particular types or scales of water storage or water access. It will identify the types and scales of water storage and access arrangements that might be possible, and the likely consequences (both costs and benefits) of pursuing these possibilities. Having done that, it will not recommend preferred development possibilities, nor comment on the required regulatory requirements to make those water resources available. The Assessment will not assume a given regulatory environment. It will evaluate the availability and use of resources in accordance with existing regulations, but will also examine resource use unconstrained by regulations, to ensure that the results can be applied to the widest possible range of uses for the longest possible time frame. It is not the intention – and nor will it be possible – for the Assessment to address all topics related to irrigation and aquaculture development in northern Australia, due to time and/or resource constraints. Important topics that are not addressed by the Assessment (e.g. impacts of irrigation development on terrestrial ecology) are discussed with reference to, and in the context of, the existing literature. No attempt has been made to identify such topics in this report. Functionally, the Assessment will adopt an activities-based approach to the work (which is reflected in the content and structure of the outputs and products, as per Section 1.2), with the following activity groups: surface water hydrology, land suitability, agriculture viability and socio- economics, surface water storage, Indigenous values, rights, interests and development goals, and aquatic and marine ecology. 1.1.2 Program governance framework The Program Governance Committee will provide high-level governance and leadership to the Roper River Water Resource Assessment. The Program Governance Committee will meet every 6 months and act as a conduit to government stakeholders. The Assessment will also have a steering committee, which will guide the Roper River Water Resource Assessment Team. The committee will regularly report to key stakeholders on the program, and ensure that the expectations of stakeholders are considered and responded to appropriately. The Roper River Water Resource Assessment Team will plan, manage and deliver the Assessment. The team will consist of CSIRO staff, augmented with contracts to jurisdictions, universities and private contractors, where necessary. 1.2 Reporting schedule The contracted deliverables for the Assessment are a suite of reports: •Technical reports present scientific work at a level of detail sufficient for technical and scientificexperts to understand the work. Each of the activities of the Assessment has a correspondingtechnical report. •A catchment report – synthesises key material from the technical reports, providing well- informed but non-scientific readers with the information required to make decisions about theopportunities, costs and benefits associated with irrigated agriculture. •An overview report – is provided for a general public audience. •A fact sheet – is provided to explain key findings for a general public audience. The dates for completion of key deliverables are listed in Table 1-1. Table 1-1 Key deliverables for the Assessment For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au 1.3 Review process As part of CSIRO’s internal quality assurance process, all reports produced by the Assessment will be reviewed. CSIRO will manage the review process in accordance with CSIRO’s ePublish protocols. Technical reports will be reviewed by at least two reviewers. Additional comment will be sought from the Northern Territory Government, depending on the topic and content. A combination of external and internal reviewers will be used. After review and revisions in response to the review, each report will be sent to the Department of Infrastructure, Transport, Cities and Regional Development for final approval. 1.4 Past studies and links to relevant current projects A key component of the Assessment will be the collation and review of relevant literature, which will be a prerequisite for all activities. The methods described in this report will be modified to take into account the availability (and sometimes lack) of information on the Assessment area. The Assessment team will rely in part on the Program Steering Committee to ensure that all relevant literature is captured and to help identify local experts who should be consulted. 1.4.1 The Roper River Water Resource Assessment area The Assessment area is defined by the Roper River catchment as defined by the 1” Shuttle Radar Topographic Mission (Figure 1-1). It encompasses an area of about 79,630 km2. The largest towns in the Roper catchment are Mataranka and Ngukurr. The Roper catchment is wet–dry tropical, and rainfall is highly seasonal. The wet season (November to April) accounts for 96% of annual rainfall and 96% of annual runoff (CSIRO, 2009). Annually, potential evaporation is greater than precipitation, and approximately 14% of precipitation is transformed to runoff. Large variability in annual runoff occurs, and the strong seasonality in rainfall results in large wet-season flows and small dry-season flows (CSIRO, 2009). The ecology of the catchments is adapted to the high seasonality and variability typical of tropical river systems. Figure 1-1 The Roper catchment in the Northern Territory 1.5 Objectives and contents of this report The objective of this report is to broadly outline the methods that the Assessment intends to employ. The purpose is to openly communicate the scope of the Assessment and the proposed methods to a wide range of stakeholders, to allow them to provide feedback and engage with the Assessment team. The report also provides a mechanism for the Assessment team to acquire feedback on the proposed methods, to ensure that they are fit for purpose. The actual methods that the Assessment will use may vary as more information becomes available, and will be documented in detail in the technical reports. The Assessment is divided into six activities. Figure 1-2 illustrates the high-level linkages between the activities (in blue boxes) and the general flow of information in the Assessment. The figure does not seek to capture all linkages and dependencies between activities. For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au This report is structured to align with the following three central questions (in italics below) that encompass the four deliverable points listed in Section 1.1, as well as the activities shown in Figure 1-2: •Part I – Introduction provides an overview of the Roper catchment and defines the Assessmentarea and key concepts: –Chapter 1 – Introduction –Chapter 2 – Key concepts •Part II – Resource assessment addresses the question ‘What soil and water resources areavailable to support regional development?’ by describing the information and methods neededto identify, map and quantify the available soil and water resources. The following chapterspresent methods in Part II: –Chapter 3 – Surface water hydrology –Chapter 4 – Land suitability •Chapter 5 – Groundwater hydrology •Part III – Economic viability addresses the question ‘What are the opportunities by which waterresource development may enable regional development?’ by evaluating the opportunities foragriculture and aquaculture, water storage, and supply of water for multiple uses, includingurban and hydro-electric power generation. It also evaluates the economic costs and benefits, and regional socio-economic impacts of these opportunities. The following chapters presentmethods in Part III: –Chapter 6 –Indigenous water values, rights, interests and development aspirations and watervalues –Chapter 7 – Surface water storage –Chapter 8 – Agriculture and socio-economics •Part IV –Achieves a balance between competing priorities by addressing the question ‘What arethe likely risks and opportunities to the natural environment due to changes in the river flowregime as a result of water resource development?’ The following chapters present methods inPart IV: –Chapter 9 – Ecology •Part V – Case studies, reports, key protocols and standards describes the rationale forundertaking case studies, summarises the reports that will be delivered by the Assessment andoutlines key protocols for data management: –Chapter 10 – Case studies –Chapter 11 – Reports, products, protocols and standards. Figure 1-2 Schematic diagram illustrating the high-level linkages between the seven activities and general flow of information in the Assessment 1.6 References CSIRO (2009) Water in the Roper Region. In: Water in the Gulf of Carpentaria Drainage Division. A report to the Australian Government from the CSIRO Northern Australia Sustainable Yields Project. CSIRO Water for a Healthy Country Flagship, Australia. For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au 2 Key concepts 2.1 Water year, and wet and dry seasons The Assessment area experiences a highly seasonal climate, with the majority of rain falling between December and March. Unless specified otherwise, the wet season is defined as the 6- month period from 1 November to 30 April and the dry season as the 6-month period from 1 May to 31 October. All results in the Assessment are reported over the ‘water year’, defined as the period 1 September to 31 August, which allows each wet season to be counted in a single 12- month period, rather than being split over two calendar years (i.e. counted as two separate seasons). This is the usual convention for reporting climate statistics in northern Australia, as well as from a hydrological and agricultural assessment viewpoint. 2.2 Scenario definitions The Assessment will consider four different scenarios of climate, surface water, groundwater and economic development, as used in the Northern Australia Sustainable Yields Project (CSIRO, 2009): •Scenario A – historical climate and current development •Scenario B – historical climate and future development •Scenario C – future climate and current development •Scenario D – future climate and future development. 2.2.1 Scenario A Scenario A will include historical climate and ‘current’ development. The historical climate data will be for 110 years (water years from 1 September 1910 to 31 August 2019) of observed climate (rainfall, temperature and potential evaporation for water years). All results will be presented over this period, unless specified otherwise. Current development is defined here as the level of surface water, groundwater and economic development as at 31 August 2019. The Assessment will assume that all current water entitlements are being fully used. Scenario A will be used as the baseline against which assessments of relative change are made. 2.2.2 Scenario B Scenario B will include historical climate and future water resource development. Scenario B will use the same historical climate data as Scenario A. Future water resource development will be described by each case study storyline, and river inflow and water extractions will be modified accordingly. Case study storylines will be developed in consultation with key stakeholders (see Chapter 9). The impacts of changes in flow regime due to future development will be assessed and compared to other scenarios including: •impacts on instream, riparian and near-shore ecology •impacts on Indigenous water values •economic costs and benefits •opportunity costs of expanding irrigation •institutional, economic and social considerations that may impede or enable adoption ofirrigated agriculture. 2.2.3 Scenario C Scenario C will include future climate and current development. It will be based on the 110-year climate data sequence, scaled for conditions in about 2060. These climate data will be derived from a range of global climate model (GCM) projections for a 2.2 °C global temperature rise scenario, which encompasses different GCMs from the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) under an RCP8.5 emissions scenario (RCP8.5 is one of four greenhouse gas concentration (not emissions) trajectories adopted by the IPCC for its Fifth Assessment Report (AR5) in 2014). The projections will then be used to modify the observed historical daily climate sequences using a simple scaling technique as outlined in Charles et al., (2016). Like Scenario A, current development is the level of surface water, groundwater and economic development as at 31 August 2019. 2.2.4 Scenario D Scenario D is future climate and future development. It will use the same future climate series as Scenario C. River inflow, groundwater recharge and flow, and water extraction will be modified to reflect proposed future development, in the same way as in Scenario B. 2.3 Case studies The case studies in the Assessment will be used to provide examples of how information produced by the Assessment can be assembled to help readers ‘answer their own questions’. They will also help readers understand the type and scale of opportunity for irrigated agriculture or aquaculture in selected geographic parts of the Assessment area, and explore some of the nuances associated with greenfield developments in the Roper catchment. Importantly, the case studies are illustrative only. They are not designed to demonstrate, recommend or promote particular development opportunities being proposed by individual development proponents, nor are they CSIRO’s recommendations on how development in the Roper catchment should unfold. However, they are designed to be realistic representations. That is, the case studies will be ‘located’ in specific parts of the Assessment area, and use specific water and land resources, and realistic intensification options. For more information on the case studies, see Chapter 9. 2.4 References Charles S, Petheram C, Berthet A, Browning G, Hodgson G, Wheeler M, Yang A, Gallant S, Vaze J, Wang B, Marshall A, Hendon H, Kuleshov Y, Dowdy A, Reid P, Read A, Feikema P, Hapuarachchi P, Smith T, Gregory P, Shi L. (2016) Climate data and their characterisation for hydrological and agricultural scenario modelling across the Fitzroy, Darwin and Mitchell catchments. Australia: CSIRO; 2016. https://doi.org/10.25919/5b86ed38d15a6 CSIRO (2009) Water in the Roper Region. In: Water in the Gulf of Carpentaria Drainage Division. A report to the Australian Government from the CSIRO Northern Australia Sustainable Yields Project. CSIRO Water for a Healthy Country Flagship, Australia. Part II What soil and water resources are available to support regional development? 3 Surface water hydrology The surface water hydrology activity uses a modelling framework to obtain water storage and flux estimates over various spatial and temporal scales across the Roper catchment. The key questions that this activity seeks to address in the Roper catchment include: • How much water has discharged from the catchment each day, month and year since 1910? • What are the opportunities to use surface water for multiple uses? • Where is most runoff generated? • How does the persistence of waterholes relate to streamflow in different river reaches? • With what degree of reliability can increasing volumes of water be extracted in different parts of the Roper catchment, and how will streamflow be perturbed downstream? • What is the maximum flood extent, and how do flood extent and duration vary with different sized events? • How do flood extent and duration change under different levels of water harvesting and large dam development? • How would changes in future climate potentially affect streamflow and water resource development in the Roper catchment? This chapter provides an overview of the key surface water modelling frameworks to be used in the Assessment. This is followed by a brief description of the available data, and an overview of the model calibration and model experiment process. Examples of use of the model output are then provided, and surface water quality is discussed briefly. 3.1 Introduction Streamflow in the Roper catchment is highly seasonal, reflecting contrasting wet and dry seasons. The catchment is relatively flat and features extensive floodplains of low relief. The lower portions of the river are tidally affected. The Roper River shows a tidal influence upstream as far as Roper Bar (150 km from Roper River mouth). 3.2 Model overview Three types of interdependent models will be used: (i) landscape, (ii) river system, and (iii) hydrodynamic. Broadly speaking, the landscape model simulates fluxes that will be used as input to the river system model and the hydrodynamic model. Output from the river system model will be used as an upstream boundary condition for the hydrodynamic model. 3.2.1 Landscape models Landscape models are used to estimate the hydrological response of landscapes (at the scale of interest). The most widely used and recognisable landscape model is a rainfall-runoff model, which features calibrated parameters, and typically estimates runoff at a point or grid cell from daily precipitation and potential evaporation inputs. The Sacramento model (Burnash et al., 1973) will be used in the Assessment to simulate a range of landscape water fluxes, but the output of primary interest for the purposes of the Assessment is runoff. 3.2.2 River system models The river system models aggregate runoff estimates obtained from the conceptual rainfall-runoff model and routs the water along a stream network. Streamflow is usually estimated at various points along the river system. These points are typically referred to as nodes, with connecting stream lines referred to as ‘links’ or reaches. Each link features various sub-models to estimate in- reach processes such as routing, irrigation diversion, losses to groundwater, losses to floodplains, anabranch flow and reservoirs. Each reach or link uses inflows from reaches upstream, climate data, configuration information and calibrated parameters to estimate states related to configured processes and estimate flow at the end of the reach. The models could be used with or without a loss function to improve goodness of fit. The river system modelling activity will use an extended version of the Australian Water Resource Assessment – River (AWRA-R) model, (Dutta et al., 2015a). AWRA-R can be used with a conceptual rainfall-runoff model such as Sacramento (Burnash et al., 1973). The AWRA-R model is very flexible, enabling it to be quickly modified, as a result of its simple reach-by-reach operation where each reach is simulated in full before the simulation of the next reach. The AWRA-R model is also designed to enable fast run times and can be used in conjunction with a variety of auto-calibration routines (Dutta et al., 2015b). This will enable modelling experiments to be rapidly undertaken to ascertain the most appropriate conceptualisation and calibration strategies. Models will be formulated with input from Northern Territory Government hydrologists to ensure that the river system models have utility for jurisdictional needs. Additionally, finalised models will be made available via web-link and graphical user interface, allowing anyone to run scenario analysis of the Roper catchment. 3.2.3 Hydrodynamic models Hydrodynamic models are physically based models that explicitly simulate the movement of floodwaters through waterway reaches, storage elements and hydraulic structures. The Roper River floodplain inundation modelling will be implemented using MIKE FLOOD (DHI, 2007; DHI, 2009) which is a coupled one-dimensional–two-dimensional model developed by DHI. The floodplain will be represented by a two-dimensional flexible triangular mesh and simulated using MIKE 21, while the river channel will be modelled with a one-dimensional model called MIKE 11. The benefit of using this approach over MIKE 21 alone is that it allows more control over the river dynamics and therefore should give more accurate representations of overbank flows. The data requirements for the floodplain modelling activity will be a recently collected and corrected light detection and ranging (LiDAR) digital elevation model (DEM) for two-dimensional flexible mesh generation, and river bathymetry for the cross-section input used in the one- dimensional component. MIKE FLOOD also allows for hydrological processes such as infiltration, rainfall and evaporation; however, these modules require soil property data as well as climate data. Importantly, gauged stream level and flow data are used as inputs to the simulations and are also used to calibrate/evaluate the model. Finally, satellite imagery such as Landsat (various satellites) is used to evaluate the predicted inundation. The availability of the data is likely to determine the flood events that are used for calibration and evaluation. 3.3 Data availability The surface water storage activity will build on work previously undertaken in the Roper catchment, namely the Northern Australia Sustainable Yields (NASY) Project (CSIRO, 2009). As part of the NASY project, runoff was generated using an ensemble of conceptual rainfall-runoff models (Petheram et al., 2009). In the Roper River Water Resource Assessment, a more complex suite of hydrological models will be used than were used in NASY because more detailed modelling is required. Furthermore, a greater length of streamflow data are now available since the NASY project was completed in 2008. The Roper River Water Resource Assessment will have greater data requirements than the NASY project because more detailed analysis and modelling are required to address the objectives of the Assessment, and more physically based models will be used. The primary dataset used for all surface water model calibration is stream gauge data. For the river system modelling, all available gauges in the Roper catchment will be assessed for use; however, landscape modelling may also include nearby gauges. In the Roper catchment, 11 separate gauge records of variable quality and duration have been identified. These will be assessed for their inclusion in the river system node–link network. Gauge locations for the Roper catchment are shown in Figure 3-1. Figure 3-1 Roper catchment showing stream gauge locations and maximum flood extent (MODIS) 3.4 Model calibration and modelling experiments 3.4.1 Input data and data collection Climate data will be sourced from the SILO database, subject to data quality checks. The Assessment will use the hydrologically corrected Shuttle Radar Topography Mission (SRTM-H) DEM as the baseline elevation dataset. It is supplemented with LiDAR data, which has been acquired by CSIRO. Stream bathymetry data may be acquired within the main stream channel (subject to budget and time constraints). These data will be spliced back into the SRTM DEM-H. These high-resolution elevation data are particularly useful in helping to parameterise channel features in the MIKE FLOOD model. Roughness information is required to parameterise the MIKE FLOOD model. This will be derived from vegetation mapping data and, potentially, satellite radar data. For more information on this figure or equation or table, please contact CSIRO on enquiries@csiro.au A limited number of pressure sensors may be deployed in selected persistent waterholes in the Roper catchment. Waterholes will be selected in consultation with the ecology activity (Chapter 8) and the Northern Territory Government, and by analysis of the Water Observations from Space (WOfS) dataset. The on-ground sensors will be used to try to establish ‘commence to fill’ discharge and the flow required to fill selected waterholes after each dry season. This information can be used to make the output from the river system models (typically daily time series of water fluxes) more ecologically meaningful. In consultation with the Northern Territory Government and the surface water storage activity, field data may be collected to help establish the physical (minimum) limits to water extraction (i.e. minimum depth and discharge at which water could be pumped) in key reaches of the Roper catchment. 3.4.2 Model calibration Sacramento The following modelling experiments to support the calibration of the Sacramento model will be undertaken: • The Assessment will investigate various strategies for making best use of the available streamflow data. These will include modelling experiments to determine an appropriate data quality and length threshold for use in the calibration process. • A variety of objective functions will be explored using the data from the Roper catchment, to best simulate both low and high flows. • A single set of parameters will be determined for the Sacramento model for each of two approaches: – parameters calibrated to gauges in the vicinity of the Roper catchment – parameters calibrated to a subset of gauges based on either perennial streams or ephemeral streams, since dry-season groundwater discharge is obvious in some parts of the catchment, but not others. The parameter set that proves to have the best predictive capacity will be used to estimate runoff at all locations across the Roper catchment at a 5-km grid. The model parameters will be evaluated on an independent subset of catchments, using various goodness-of-fit measures and compared to the result of a conceptual rainfall-runoff models. AWRA-R Calibration of the AWRA-R model will proceed as follows: • A baseline node–link network will be established for the Roper catchment. This is simply the physical connection of river reaches with each other and is required to enforce the calculation order for each reach (reach models are run upstream to downstream in a workflow). This step will be influenced by the availability and suitability of gauge data, and physical aspects of the river system. The model will be structured so that nodes are also situated at sites potentially suitable for surface water storage (surface water storage activity), adjacent to land suitable for irrigated agriculture (land suitability activity), near locations of ecological interest (ecology activity), and of interest to Traditional owners (Indigenous water values, rights, interests and development activity), and so as to simulate streamflow at the boundary of the modelled floodplains.. • If experimental results warrant, gauge data will be filtered to remove any data with unacceptable quality codes. • Sub-models that enable various processes (e.g. overbank flow, groundwater loss) can be switched on or off. • Sacramento runoff estimates will be aggregated to provide estimates of ungauged flow (i.e. residual inflow) for each river reach, or where gauge data are available, Sacramento will be calibrated locally in conjunction with AWRA-R parameters. • The observed streamflow record in the headwater catchments will be ‘patched’ with Sacramento aggregated runoff estimates, i.e. simulated runoff will be used where there are gaps in the headwater observed time series. Calibration against observed flows will be undertaken using a ‘shingle’ approach where all reaches in a portion of the catchment will be calibrated simultaneously. Each portion of the catchment overlaps to ensure that parameters transition smoothly between upstream and downstream shingles. The differential evolution algorithm (Mullen et al., 2011) will be used for calibration parameters search. The objective function will be a combination of Nash–Sutcliffe efficiency on root transformed values and mean annual absolute bias: where 𝐸𝐸𝑑𝑑 0.5 is the Nash–Sutcliffe efficiency of the root transformed daily flow, 𝜀𝜀365 is the normalised annual error, 𝜀𝜀ℎ𝑓𝑓 is the normalised error in the highest 20 flow days, 𝐸𝐸𝐸𝐸𝐸𝐸90 is the exceedance probability difference of the 90%, non-zero exceedance value of the observed data in comparison to the simulated data: 𝐸𝐸𝐸𝐸𝐸𝐸90=|𝑃𝑃90(𝑄𝑄𝑜𝑜𝑜𝑜𝑜𝑜)−𝑃𝑃90(𝑄𝑄𝑠𝑠𝑠𝑠𝑠𝑠)| where 𝑃𝑃90 refers to the 90% exceedance probability. High flow error calculates the normalised difference between the 20 highest observed flows and the 20 highest simulated flows. 3.5 References Burnash, R.J.C, Ferral, R.L. & McGuire, R.A. (1973) A generalized streamflow simulation system: conceptual modeling for digital computers, Technical Report, Joint Federal and State River Forecast Center, US National Weather Service and California Department of Water Resources, Sacramento, CA. CSIRO (2009) Water in the Gulf of Carpentaria Drainage Division. A report to the Australian Government from the CSIRO Northern Australia Sustainable Yields Project. CSIRO Water for a Healthy Country Flagship, Australia. DHI (2007) MIKE FLOOD: modelling of river flooding: step-by-step training guide. DHI, Denmark. DHI (2009) MIKE 21 flow model: scientific documentation. DHI, Denmark. For more information on this figure or equation or table, please contact CSIRO on enquiries@csiro.au. Dutta D, Kim S, Hughes J, Vaze J and Yang A (2015a) AWRA-R technical report. CSIRO Land and Water, Australia. Dutta D, Kim S, Hughes J, Yang A and Vaze J (2015b) AWRA-R version 5.0 calibration tools. CSIRO Land and Water Flagship, Australia. Mullen KM, Ardia D, Gil DL, Windover D and Cline J (2011) DEoptim: an R package for global optimisation by differential evolution. Journal of Statistical Software 40(6), 1–26. Petheram C, Rustomji P and Vleeshouwer J (2009). Rainfall-runoff modelling across northern Australia. A report to the Australian Government from the CSIRO Northern Australian Sustainable Yields Project. CSIRO Water for a Healthy Country Flagship, Australia. 4 Land suitability 4.1 Introduction A fundamental input to the study of water resource development, principally for agricultural purposes, is an understanding of the soil and landscape resources available, their spatial distribution and the limitations to their use. Primarily, an understanding of the potential suitability of soils for a range of crops, planting seasons and irrigation management will be explored, although land suitability estimates will also be made within the Assessment for aquaculture and for earthen ringtanks. The activity will use a combination of existing national data, field collected data and modelled outputs and is the largest single activity within the Assessment. A digital soil mapping (DSM) approach will be taken to produce a set of raster attribute data (which can be displayed as maps) at a pixel resolution of 3 arc-seconds (approx. 90 m) or finer. These attributes will then be used within a land suitability framework to produce an estimate of land suitability for a range of specific land uses using a 5-class scale from highly suitable to unsuitable, again in data and map form at 90 m resolution or finer. Estimates of reliability for these data will also be produced using novel methods. The land suitability rule framework will be built on a combination of existing frameworks within CSIRO and the Northern Territory Government, both of which are compatible with the land evaluation approach of the Food and Agriculture Organization (FAO) of the United Nations. The outputs of this activity can be considered useful at a regional (broad) scale (approx. 1:250,000 scale) rather than for individual property or enterprise planning. The activity will make use of the rich history of soil and landscape investigation by the Northern Territory Government within the Roper catchment (e.g. Aldrick and Wilson, 1992; Burgess et al., 2015; Day and Wood, 1976; McGrath and Andrews, 2019) and will make use of these legacy data wherever possible. The work also draws heavily on the methods and practices for broad-scale land evaluation from the Flinders and Gilbert Agricultural Resource Assessment (Bartley et al., 2013; Harms et al., 2015; Thomas et al., 2015) and the Northern Australia Water Resource Assessment (NAWRA) (Thomas et al., 2018a; Thomas et al., 2018b). The key questions that this activity seeks to address in the Roper catchment include: • What is the total area of land with characteristics suitable for a particular land use, principally irrigated and dryland cropping, and where in the catchment can this land be found? • What is the total area of different soil types and where in the catchment can they be found? • What are the soil limitations for specific land uses, such as irrigated agriculture, and where are they located? • What is the estimated reliability of the information provided above? 4.2 Workflow Figure 4-1 shows the broad workflow undertaken for this activity. The workflow highlights the tasks of soil sampling design, DSM and land suitability analysis, while also showing the dependencies feeding into these, including environmental covariates, soil attribute data, data quality metrics, and the land suitability rule framework that drives the land suitability analysis. Figure 4-1 Land suitability analysis workflow, key inputs and processes (Thomas et al., 2018a) Brown components reflect the Digital Soil Mapping component (as described in Thomas et al., 2018a) while blue components reflect the land suitability component (as described in Thomas et al., 2018b). The ‘data quality assessment’ sits across both components. 4.2.1 Soil sampling design As well as using legacy soil data, new soil data will be collected in the field at approximately 200 new sites (Figure 4-2). The number of sampling points is determined a priori as a function of the budget and logistical considerations, such as access. A stratified random sampling approach (McKenzie et al., 2008) will be used to remove human bias in the selection of soil sampling sites, and to maximise the spread of sites so the full range of soil– landscape variability across the catchment is sampled. A non-biased soil sampling design is a prerequisite of reliable DSM. The sampling design will use conditioned Latin hypercube sampling (cLHS) described in full in Minasny and McBratney (2006). Use of cLHS ensures sampling points capture the empirical distribution of the environmental covariates chosen to represent the full variability of soils across the Assessment area. For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au Figure 4-2 Collecting soil cores in the field using a vehicle-mounted push core rig. The collected soil will be analysed in the field and a subset subjected to laboratory analysis Photo: CSIRO 4.2.2 Environmental covariates The covariates will be selected as proxies for factors of soil formation (i.e. climate, parent material, biota and topography) (Jenny, 1941). They will then be used in two tasks within the DSM approach: (i) the selection of new sampling sites and (ii) predicting new soil attributes using DSM (Figure 4-1). More than 30 covariates will be tested, including those related to soils, climate, vegetation and bare ground, relief, parent material and landscape age. Selection of covariates will be based on those in Table 2-2 from Thomas et al. (2018a) using the framework of Jenny (1941) and McBratney et al. (2003) but will also consider several newly released datasets. 4.2.3 Soil attributes (properties) Soil attribute, or soil property, information will be collected directly in the field and through subsequent lab analysis (Figure 4-3). For this Assessment, these data will come from newly collected soil data and from legacy data collected previously by the Northern Territory Government (see Section 4.1 for references). Attribute data collected in the field include those which indicate soil physical properties (e.g. soil depth, field texture), soil chemistry (e.g. field pH, dispersion, surface salinity), and risk (e.g. erosion) while lab analyses provide estimates of such things as particle size (% sand, % silt, % clay), cation exchange capacity, sodicity, and pH at each depth within the profile. For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au Figure 4-3 Soil sample being extracted from coring tube in the field Photo: CSIRO 4.2.4 Digital soil mapping (soil attribute layers) The DSM modelling approaches rely on correlative models that establish statistical relations between soil observations and data at points and covariates (McKenzie and Ryan, 1999). DSM models can be expressed as statistically based rules representing the relationship between (i) soil data at the sampling sites and (ii) the values of the covariates at these sites. Multiple, co- registered covariates are used in environmental correlation – effectively in a stack of raster covariates (predictors). The soil attribute to be mapped is predicted at an unsampled location using the data values of the covariates in the stack and the rules. This process of rule-to-covariate matching is applied to the whole area of interest (raster stack area) to compile the complete final soil map. The environmental correlation approach can be thought of as a digital analogue of the traditional soil mapping method, which relies on experts to build models (rules) from patterns of relief, drainage or vegetation (Hudson, 1992). In the DSM analogue, the expert is represented by the statistical modelling process. A random forest approach (Breiman, 2001) will be used. The approach constructs a multitude of decision trees during the algorithm training phase. Decision trees are ideally suited for the analysis of high-dimensional environmental data; a mix of continuous and categorical covariates that exhibit non-linear relationships, high-order interactions, and missing values can be used to predict continuous soil attributes (regression trees) or categorical ones (classification trees). A number of modelled soil attribute layers will be produced (at 3 arc-second resolution or finer) including soil pH, clay content, A-horizon depth, soil depth, plant available water capacity, For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au permeability, drainage, rockiness, erodibility, exchangeable sodium percentage, surface condition, structure, surface salinity, texture and microrelief. A data layer (which can be displayed as a map) will be used to produce soil generic groups (SGGs) principally as a communication product. The SGGs represent the main soil types of northern Australia. Soils within a group share a similar profile morphology and soil chemical and physical characteristics in terms of general land use potential. The approach used to allocate the SGG will be to classify the soil at each field site according to the Australian Soil Classification (Isbell and National Committee on Soil and Terrain, 2016) and then allocating the soil to an SGG. 4.2.5 Data quality assessment An iterative process of data quality assessment will allow for improvements in the attribute layers and the SGG layer produced within the DSM process and in the land suitability analysis. The DSM approach allows for production of companion maps of reliability in the prediction surfaces that show where the soil attribute data are more or less reliable, so that people making decisions or modelling users (e.g. hydrologists, agronomists) can make objective decisions about how to apply the data for their requirements. A major benefit of DSM compared to traditional soil mapping is that it is possible to statistically quantify and map the uncertainty associated with the soil attribute prediction at each pixel. Quality assessment of the DSM will be conducted using (i) statistical (quantitative) methods, i.e. testing the quality of the DSM models using data withheld from model computation, estimating the reliability of the model outputs, collecting independent external validation data (Brus et al., 2011), and (ii) on-ground expert (qualitative) examination of outputs during a validation field trip in the late dry season of 2020. This validation trip will use a set of independent sites, again chosen using a statistical approach based on cLHS. Furthermore, expert knowledge will be used to highlight, and amend where necessary, any attribute layers that don’t appear credible. 4.2.6 Land suitability framework The land suitability framework will be built on a combination of existing frameworks within CSIRO and the Northern Territory Government. It will provide the set of rules for determining the potential of land for specific land uses on the basis of the local range of environmental attributes and qualities (Rossiter, 1996), collectively termed limitations. In this Assessment, the land uses will be principally agricultural (i.e. crop by season by irrigation type) but will also be applied to aquaculture and to earthen ringtanks. The soil attribute layers will be combined into approximately 20 limitations. These limitations will include such things as permeability, rockiness, irrigation efficiency, nutrient balance, plant available water capacity and soil physical restrictions. These edaphic components of land suitability mostly relate to soil attributes that have a key bearing on the growth and productivity of irrigated and rainfed crops, or the amount of land preparation and maintenance of farming infrastructure needed that may affect the financial viability of the irrigation enterprise. For example, soil permeability affects the rate of water application, and rockiness relates to the intensity of rock picking required in land preparation, root crop harvesting and wear on machinery. A further limitation, which can be applied retrospectively, will be the consideration of landscape complexity. That is, the extent to which the size and shape of contiguous pixels of suitable land follow spatial patterns that might allow or prohibit development. While the framework generally follows the FAO approach to land evaluation (FAO, 1976; FAO, 1985) it differs from the strict FAO approach, which also includes a range of social (e.g. land tenure), environmental (e.g. water availability, flooding risk) and farm-scale economic (production and industry development) aspects considered elsewhere in the Assessment. 4.2.7 Land suitability analysis The land suitability analysis is the final step in the process of determining the suitability of each pixel of land for a range of land uses and forms the basis for summary statistics showing the amount and location of land suitable for specific land uses. The analysis is done on a pixel-by-pixel basis for each individual land use to compile the corresponding 5-class suitability map. For each pixel, for each land use, for each limitation, the analysis uses the rules from the land suitability framework to allocate one class from a 5-class land suitability rating (Table 4-1). The classes range from Class 1 (highly suitable) to Class 5 (unsuitable). The overall suitability for that pixel, for that land use, is taken as the limitation with the highest class (most unsuitable) rating. That is, the overall land suitability class at that location (for that land use) is based on the most limiting factor for that land use. In places where the suitability class does not match expert expectations and/or experience (e.g. experienced on-ground during the later dry-season validation field trip), the limitations at that location are interrogated. Where the most limiting factor does not conform to the expectations of the experts (i.e. the influence of the limitation appears too great on the mapped outcome because the limitation setting is too conservative), the thresholds used in the rule may be adjusted. This process may be repeated numerous times for numerous limitations until the final implementation of the rule set satisfies expert expectations and evidence. Finally, a land versatility map will be generated for the Roper catchment that scores the suitability ratings for each land use for each pixel. High scoring areas of the map indicate that numerous crops may be grown there (i.e. there is greatest versatility for cropping in these areas). Table 4-1 Land suitability classes based on FAO (1976) and adapted from DSITI and DNRM (2015) and van Gool et al. (2005) For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au 4.3 References Aldrick JM and Wilson PL (1992) Land systems of the Roper River catchment, Northern Territory. Conservation Commission of the Northern Territory. Technical Report – Number 52. Northern Territory of Australia, Palmerston. Bartley R, Thomas MF, Clifford D, Phillip S, Brough D, Harms D, Willis R, Gregory L, Glover M, Moodie K, Sugars M, Eyre L, Smith DJ, Hicks W and Petheram C (2013) Land suitability: technical methods. A technical report to the Australian Government from the Flinders and Gilbert Agricultural Resource Assessment, part of the North Queensland Irrigated Agriculture Strategy. CSIRO Water for a Healthy Country and Sustainable Agriculture flagships, Australia. Breiman L (2001) Random forests. Machine Learning 45(1), 5–32. DOI: 10.1023/a:1010933404324. Brus DJ, Kempen B and Heuvelink GBM (2011) Sampling for validation of digital soil maps. European Journal of Soil Science 62, 394–407. Burgess J, McGrath N, Andrews K and Wright A (2015) Soil and land suitability assessment for irrigated agriculture in the Larrimah area, Sturt Plateau. Agricultural Land Suitability Series – Report 1. Northern Territory Department of Land Resource Management Technical Report 19/2015D. Northern Territory of Australia, Palmerston. Day KJ and Wood BG (1976) Soils of the upper Roper plains – Moroak Station, NT Land Conservation Section, Animal Industry and Agriculture Branch, Department of the Northern Territory, Darwin. DSITI and DNRM (2015) Guidelines for agricultural land evaluation in Queensland. Queensland Government (Department of Science, Information Technology and Innovation and Department of Natural Resources and Mines), Brisbane, Australia. FAO (1976) A framework for land evaluation. Food and Agriculture Organization of the United Nations, Rome. FAO (1985) Guidelines: land evaluation for irrigated agriculture. Food and Agriculture Organization of the United Nations, Rome. Harms B, Brough D, Philip S, Bartley R, Clifford D, Thomas M, Willis R and Gregory L (2015) Digital soil assessment for regional agricultural land evaluation. Global Food Security 5(0), 25–36. DOI: Global Food Security journal website . Hudson BD (1992) The soil survey as paradigm-based science. Soil Science Society of America Journal 56(3), 836–841. DOI: 10.2136/sssaj1992.03615995005600030027x. Isbell RF and National Committee on Soil and Terrain (2016) The Australian Soil Classification. CSIRO Publishing, Melbourne. Jenny H (1941) Factors of soil formation, a system of quantitative pedology. McGraw-Hill, New York. McBratney AB, Santos MLM and Minasny B (2003) On digital soil mapping. Geoderma 117(1–2), 3– 52. DOI: 10.1016/s0016-7061(03)00223-4. McGrath N and Andrews K (2019) Soil and land suitability assessment for irrigated agriculture on part of Beswick Aboriginal Land Trust. Rangelands Division, Department of Environment and Natural Resources. Agricultural Land Suitability Series – Report 13. DENR Technical Report 16/2018D. Northern Territory of Australia, Palmerston. McKenzie NJ and Ryan PJ (1999) Spatial prediction of soil properties using environmental correlation. Geoderma 89(1–2), 67–94. McKenzie NJ, Grundy MJ, Webster R and Ringrose-Voase AJ (2008) Guidelines for surveying soil and land resources. CSIRO Publishing, Collingwood, Victoria. Minasny B and McBratney AB (2006) A conditioned Latin hypercube method for sampling in the presence of ancillary information. Computers & Geosciences 32(9), 1378–1388. DOI: 10.1016/j.cageo.2005.12.009. Rossiter DG (1996) A theoretical framework for land evaluation. Geoderma 72(3–4), 165–190. DOI: Geoderma journal website . Thomas M, Clifford D, Bartley R, Philip S, Brough D, Gregory L, Willis R and Glover M (2015) Putting regional digital soil mapping into practice in Tropical Northern Australia. Geoderma 241– 242, 145–157. DOI: Geoderma journal website . Thomas M, Brough D, Bui E, Harms B, Holmes K, Hill JV, Morrison D, Philip S, Smolinski H, Tuomi S, Van Gool D, Watson I, Wilson PL and Wilson PR (2018a) Digital soil mapping of the Fitzroy, Darwin and Mitchell catchments. A technical report from the CSIRO Northern Australia Water Resource Assessment, part of the National Water Infrastructure Development Fund: Water Resource Assessments, Australia. Thomas M, Gregory L, Harms B, Hill JV, Morrison D, Philip S, Searle R, Smolinski H, Van Gool D, Watson I, Wilson PL and Wilson PR (2018b) Land suitability of the Fitzroy, Darwin and Mitchell catchments. A technical report from the CSIRO Northern Australia Water Resource Assessment, part of the National Water Infrastructure Development Fund: Water Resource Assessments, Australia. van Gool D, Till PJ and Moore GA (2005) Land evaluation standards for land resource mapping: assessing land qualities and determining land capability in south-western Australia. Department of Agriculture and Food, Western Australia, Perth. 5 Groundwater hydrology The purpose of the groundwater hydrology activity is to examine opportunities for future groundwater development to support primary industries in the Roper catchment, principally irrigated agriculture but potentially also aquaculture. At the scale of the Roper catchment, the activity will identify and assess the most promising intermediate to regional-scale aquifers and where sufficient information exists quantify the potential opportunities for, and risks associated with, future groundwater development. In this chapter, methods are described by which groundwater resources will be assessed across the catchment involving a combination of desktop analyses, targeted field investigations, and modelling at a variety of spatial and temporal scales. It is anticipated that this work will be carried out through engagement and collaboration with the Northern Territory government, Charles Darwin University, CloudGMS and various Indigenous communities in the catchment. Much of the contextual hydrogeological information presented in the chapter has been summarised from publicly available data collated by the Northern Territory government (DENR 2021) as well as some key previous hydrogeological studies including: (i) the Northern Australia Sustainable Yields (NASY) project (CSIRO 2009) and (ii) the Gulf Water Study (Knapton 2009b; Knapton 2009a; Zaar 2009). The key questions that this activity seeks to address in the Roper catchment include: • What types of aquifers exist and what is the nature of the flow systems they host? • What are the important attributes that help identify aquifers in the catchment as promising for future groundwater resource development and how do they vary spatially? • Can a range in recharge for these aquifers be estimated and are these ranges reasonable when considering rainfall, runoff, evapotranspiration, and groundwater levels? • Which river or creek reaches have evidence of strong groundwater – surface water connectivity and which aquifers support their persistence? • What types of vegetation are utilising groundwater for transpiration, where do they occur, and which aquifers support their water use? • For the most promising aquifers identified, what component of their water balance can be estimated with some level of confidence and what components remain uncertain? • What are the ranges in potential extractable volumes for the most promising aquifers? • What areas pose a risk of irrigation-induced watertable rise and secondary salinisation? 5.1 Regional geology and hydrogeology of the Roper catchment 5.1.1 Regional geology The Roper catchment has a complex geological history traversing parts of four geological basins: (i) the McArthur Basin which underlies the north, centre and east of the catchment and (ii) the connected Daly, Wiso and Georgina basins which underlie the south and west of the catchment. The oldest rocks of the catchment are the central Proterozoic undifferentiated fractured rocks which underlie the middle reaches of the Roper River and are comprised mostly of silicified sandstone, siltstone, mudstone, greywacke and granite (CSIRO 2009; Knapton 2009b; Zaar 2009) see Figure 5-1. To the north east of the fractured rocks, are the Mesoproterozoic rocks of the McArthur Basin comprised mostly of sandstone, siltstone and dolostone which underlie the northern tributaries of the Roper River including the Wilton and Mainoru rivers and Flying Fox Creek with minor outcrops and subcrops around Ngukurr (Knapton 2009b; Zaar 2009). In the south and west of the catchment, are the Cambrian volcanic and carbonate rocks of the Daly, Wiso and Georgina basins. The volcanic rocks are mostly comprised of basalt, while the carbonate rocks are mostly comprised of limestone and dolomitic limestone, with minor mudstone and siltstone (CSIRO 2009; Knapton 2009b). The youngest rocks across the catchment are the: (i) Cretaceous sandstone and mudstone which overlie the carbonate rocks in the south west and north east of the catchment and (ii) Cenozoic sediments including alluvium that occurs along the river/creek valleys and floodplains, and the coastal sand plain in the east (Zaar 2009). 5.1.2 Regional hydrogeology There are three main types of aquifers across the Roper catchment: (i) fractured rocks, (ii) fractured and karstic carbonate rocks and (iii) sedimentary sandstones (CSIRO 2009; Zaar 2009). These aquifer types occur in a variety of hydrogeological units (ie. geological units hosting aquifers) across the catchment and host groundwater flow systems of varying scale. That is, some hydrogeological units host local-scale flow systems while others host intermediate to regional- scale flow systems. Local-scale flow systems have very short distances between recharge areas where water enters the groundwater system and discharge areas where water exits the system (i.e. a few hundred metres to a few kilometres). Whereas, intermediate to regional-scale flow systems have much larger distances between recharge and discharge areas (i.e. several kilometres to tens or hundreds of kilometres). It is these larger groundwater flow systems that provide greater opportunities for groundwater development because they often: (i) store and transmit larger amounts of water, (ii) provide opportunities for development away from existing users and groundwater dependant ecosystems (GDE’s) and (iii) have greater potential to coincide with larger areas of soils prospective for agricultural intensification. Data and information for different hydrogeological units and the groundwater flow systems they host vary significantly across the Roper catchment. For example, there are four ‘known’ hydrogeological units with groundwater systems that could potentially yield sufficient water for irrigated agriculture. However, only the Tindall Limestone Aquifer (TLA) and its equivalents (Gum Ridge Formation) hosted in the Cambrian limestone underlying the south west of the catchment in the upper Roper has been well characterised (Figure 5-1). The TLA has had an extensive amount of drilling, water level monitoring, water quality sampling and pump testing. Bore depths for the aquifer are typically <150 m below ground level (mBGL), bore yields are variable given the fractured and karstic nature of the aquifers but can be significant (i.e. up to 130 L/second) and transmissivities range between 2,000 and 5,000 m2/day (Knapton 2009b; DENR 2017, 2021). In addition, a groundwater balance model and a water allocation plan have already been developed for the aquifer (Knapton 2009b; DENR 2017). Currently, the TLA between Mataranka and Daly Waters has a total of ~26 GL/year of groundwater license entitlements currently allocated for beneficial use (almost entirely agricultural use), with another ~40 GL/year of groundwater unallocated (DENR 2017). There is some useful information available for the three other hydrogeological units hosted in the Mesoproterozoic carbonate rocks (the Dook Creek Formation (DCF) and its equivalents – Knuckey Formation and Mount Birch Sandstone) in the north east of the catchment (Figure 5-1). Historical pumping test data on the DCF around Beswick and Bulman indicate a productive aquifer with reported transmissivities at both locations of 700 and 6,000 m2/day respectively (Knapton 2009b). However, further work is required to characterise the hydrogeological framework of the aquifers and conceptualise and quantify groundwater flow processes (i.e. recharge, throughflow, discharge, inter-aquifer and groundwater – surface water connectivity). For these other hydrogeological units that could potentially support development of primary industry (and potentially other unidentified local/intermediate scale units), the groundwater hydrology activity would seek to: (i) provide a better understanding of key hydrogeological characteristics (i.e. aquifer extent and thickness, aquifer properties, bore yields and water quality) and (ii) where possible important components of the groundwater balance (i.e. recharge rates and sources of discharge). For those hydrogeological units where there is already a high level of work that has been undertaken (i.e. the TLA) and there is an opportunity to build upon this work, the groundwater hydrology activity will seek to provide more detailed information that could be used to underpin future groundwater planning, investment and management. For the most prospective hydrogeological units identified, and where resources are sufficient to adequately characterise the system, the groundwater hydrology activity will seek to acquire a range of more detailed information related to better understanding the costs and economics of groundwater development in specific units including information on: • Depth to water bearing formation – strongly correlated to the cost of drilling • Depth of potentiometric head – strongly correlated to the cost of pumping • Yield – influences number of bores required to meet water demand, influencing cost of development • Aquifer draw down in response to pumping – correlates to cost of pumping (increases head), but also very important to understand in terms of the potential available resource when considering hydrological impacts to existing users, GDE’s and the aquifer integrity (i.e. depletion in storage or degradation of water quality). Figure 5-1 Regional hydrogeology of the Roper catchment Figure source: Figure 4 in Knapton (2009a) 5.2 Regional hydrogeological desktop assessment A regional hydrogeological desktop assessment will be undertaken targeting both the TLA and the DCF and their equivalents. This assessment will provide an aquifer attribution to publicly available groundwater data available through the Department of Environment and Natural Resources (DENR) web mapping tool (DENR 2021). Aquifer specific hydrogeological data including water levels and quality, water chemistry, bore yield and aquifer properties will then be collated and summarised along with data published in existing literature to evaluate the amount of available information for the four different hydrogeological units. This information will then be used to identify: (i) areas where further drilling can be conducted to better characterise aquifer extents, geometries saturated thickness and properties (see Section 5.3) and (ii) identify candidate groundwater bores to implement a hydrological monitoring and groundwater sampling programs. For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au The monitoring and sampling programs will assist in further characterising, conceptualising, and quantifying groundwater flow processes (i.e. recharge, throughflow and discharge) and where possible seek to evaluate their potential for future development (see Section 5.6). In addition, information from existing literature will be used to design other desktop, field and modelling investigations to fill key knowledge gaps that will assist in underpinning future groundwater planning, investment and management of the TLA and its equivalents (see Section 5.5). 5.3 Hydrogeological Framework Refinement of the hydrogeological framework for the TLA and DCF and equivalents will be determined following an evaluation of the publicly available hydrogeological data, and through discussions with hydrogeologists at DENR and Power and Water Corporation (PWC). In addition, consultation will be undertaken with relevant Indigenous communities and the Aboriginal Areas Protection Authority prior to undertaking any proposed drilling. The drilling techniques to be employed will be selected based on previous successful drilling in areas with similar hydrogeological settings. The combination of production and monitoring bores will be constructed and installed for addressing specific hydrogeological questions such as determining aquifer hydraulic properties, discrete water level monitoring and discrete hydrogeochemistry and environmental tracer sampling to characterise groundwater flow processes (see Section 5.4). 5.3.1 Tindall Limestone Aquifer For the TLA, the current Geological and Bioregional Assessment (GBA) program (https://www.bioregionalassessments.gov.au/assessments/geological-and-bioregional- assessment-program/beetaloo-gba-region) has undertaken some investigations of the Cambrian limestone. The groundwater hydrology activity will seek to utilise, and value add to this work including reviewing the revised geological model for potential drilling locations that includes the geological units of the Wiso and Georgina basins. Discussion with DENR hydrogeologists have highlighted the need to better characterise sources of discharge from the TLA and its equivalents around Mataranka. This will assist in better understanding the inter-aquifer connectivity between the TLA and underlying hydrogeological units such as the Antrim Plateau Volcanics and the Bukalara Sandstone and equivalents. The requirement to undertake this work is consistent with findings from filed investigations on springs at Mataranka in the current GBA program. The locations for drilling are still to be determined from the regional desktop assessment and review of the geological model (see Section 5.2). However, the intention is to install bores in both the Antrim Plateau Volcanics and Bukalara Sandstone adjacent existing bores in the TLA pending approval. This will avoid further unnecessary land disturbance, provide the benefit of having purpose-built infrastructure in all three hydrogeological units at the same locations to characterise groundwater flow processes and provide the benefit of permanent infrastructure for future groundwater monitoring (see Section 5.4.3). 5.3.2 Dook Creek Formation and equivalents With regard to further charactering the hydrogeological framework for the DCF and its equivalents, PWC already have multiple production and monitoring bores in the Knuckey Formation, Mount Birch Sandstone and Yalwarra Volcanics around Ngukurr. These bores are sited in the east of the catchment and supply water to the Ngukurr community. Bore depths are typically <100 mBGL, bore yields range from 3 to 30 L/second and transmissivities range from 100 to 878 m2/day for all three units combined (DENR 2021; PWC 2021). While the outcropping/subcropping zones of these aquifers have been explored on the northern side of the river, other outcrop/subcrop zones south of the river remain poorly characterised or unexplored all together. The groundwater hydrology activity is currently reviewing hydrogeological data around Ngukurr to explore the possibility of doing further hydrogeological characterisation in this part of the catchment (see Section 5.2). The DCF and its equivalents in the north and east of the catchment is also known to host spatially extensive and productive carbonate aquifers which support spring discharge and baseflow to the Wilton and Mainoru rivers and Flying Fox Creek (Knapton 2009b; Zaar 2009). However, very little information currently exists across large areas on the saturated thickness, water quality, bore yields and aquifer properties for the formation. Knapton (2009b) has developed a ‘preliminary’ groundwater model for the formation and reports transmissivities for the aquifers ranging between 500 to 1,000 m2/day though transmissivities of up to 6,000 m2/day have been previously reported. The groundwater hydrology activity is currently reviewing hydrogeological data to explore the opportunities to undertake drilling and targeted hydrogeological investigations to evaluate the development potential of these aquifers (see Section 5.2). These aquifers do occur across large parts of Aboriginal land so engagement with Indigenous communities and working closely with the Indigenous activity will be important (see Chapter 6). 5.3.3 Aquifer hydraulic properties The collation and reinterpretation of either historical pumping test data or new data from bores drilled and tested by the groundwater hydrology activity will be useful for understanding the physical properties of aquifers and their ability to supply water at a sufficient rate and volume to support irrigation. As part of the current GBA program, transmissivity values were collated from all available (188) historical pumping tests conducted in Cambrian limestone aquifers located across the Daly, Wiso and Georgina basins. Of these, 58 tests were located within the Roper catchment. In addition, 94 historical pumping tests were conducted in other aquifers located in the Roper catchment (Tickell and Diem Phuong Nguyen 2014). The transmissivity values from these tests will be collated from bore reports across the Roper catchment. Where the aquifer tested was not recorded, this will be interpreted from bore construction and lithological or stratigraphic information. Time-drawdown data from historical pumping tests will be digitised from bore reports and reinterpreted using a range of appropriate drawdown solutions. Data obtained from the pump testing of newly drilled bores will also be interpreted. Diagnostic plots (Renard et al. 2009) of both the raw data and their temporal derivatives will be used to identify aquifer type(s) and therefore appropriate pumping test solution(s). Reinterpretation of these data will be undertaken to provide new estimates of aquifer transmission and storage parameters providing useful information on how productive the aquifers are. The latter are rarely available from historical pumping test interpretations. The industry standard software AQTESOLV (Duffield 2007) will be used to perform pumping test reinterpretation. This software package incorporates a broad range of pumping test solutions, including for both single and dual bore tests, from drawdown responses measured in one or more aquifers. Pumping test solutions will be fitted to measured time-drawdown data using a least-squares optimisation algorithm. 5.3.4 Time-series analyses of groundwater pressure data Groundwater pressures are commonly measured at a high temporal resolution (e.g. hourly or minutely) using automated loggers, which can be deployed for many months before data are collected. Logger data is already publicly available across parts of the TLA and its equivalents via DENR (DENR 2021) but additional logger data will be obtained through the implementation of a hydrological monitoring program across the both the TLA and DCF and their equivalents. This data will be useful for a range of activities including conceptualisation of groundwater flow systems using groundwater level mapping and hydrograph analyses (see Section 5.4.1) which can also be used for quantifying gross recharge (see Section 5.4.2). In addition to responses to typical hydrological drivers (such as rainfall, evapotranspiration, and extraction), the time series data obtained from loggers often contain responses to ambient drivers of relatively smaller magnitude, such as atmospheric pressure and Earth tides. Analyses of groundwater responses to these two ambient drivers provide alternative, low-cost means of (i) identifying aquifer types, including the degree of confinement (i.e. unconfined, semi-confined or confined), and (ii) estimating aquifer hydraulic properties. Groundwater responses to variations in atmospheric pressure can be characterised by barometric response functions (BRFs), which quantify the time lags associated with measured responses. Aquifer types and hydraulic properties can subsequently be interpreted from BRFs. Instantaneous responses are indicative of confined conditions. The degree of aquifer confinement can be characterised by a metric known as barometric efficiency (BE), from which estimates of specific storage can be derived. Regression deconvolution (Rasmussen and Crawford 1997) will be used to calculate BRFs. Where possible, aquifer transmission and storage parameters will be estimated by fitting additional solutions to BRFs. The method presented by Acworth et al. (2015) and improved by Rau et al. (2020) will be used to calculate BE values. Specific storage estimates will be calculated from BE values using the definition provided by Jacob (1940). Where suitable, additional poroelastic parameters will be estimated using the method presented by McMillan et al. (in review). Earth tides are driven by the movements of the Sun and Moon and the planets Mercury, Venus, Mars, Jupiter, and Saturn. These cause vertical compression and extension of the Earth’s surface. This can be observed as micrometre-scale groundwater pressure fluctuations in the subsurface below (Godin 1972). Five frequencies, ranging from 0.8 to 2.0 cycles per day, typically account for about 95% of the total Earth tide potential (Cutillo and Bredehoeft 2011). The amplitudes of these signals attenuate (decrease) as they propagate downward through the subsurface. Similarly, the velocity at which these signals propagate decreases with distance travelled into the subsurface; this is typically described by the phase lag of a signal. Reductions in both the amplitude and phase of Earth tide components at these five known frequencies can be interpreted to provide estimates of vertical hydraulic diffusivity. Theoretical Earth tide potential values will be calculated using the Hartmann and Wenzel (1995) tidal catalogue using the ETERNA software (Wenzel 1996) via the PyGTide packge (Rau 2018) for the Python language. The amplitude and phase values of groundwater responses will be estimated using both the discrete Fourier transform (Kanasewich 1981) and harmonic least squares (Schweizer et al. 2021), both implemented as part of the HydroGeoSines package (Rau et al. 2021) for the Python language. Where appropriate, hydraulic diffusivity values will be estimated using the solution presented by Boldt-Leppin and Hendry (2003), which will be converted to vertical hydraulic conductivity values where independent estimates of specific storage values are available. 5.4 Groundwater recharge and flow 5.4.1 Groundwater level mapping Spatial and temporal groundwater level observations provide information such as variations to: (i) the depth to groundwater, (ii) the physical properties of aquifers or aquitards, (iii) the saturated thickness of aquifers, (iv) the degree to which an aquifer is confined or unconfined, and (iv) the hydraulic gradient and hydrological connectivity between different bores and different aquifers compared to surface water levels. This information is useful for conceptualising groundwater flow both locally (i.e. at a given bore) or at an intermediate (i.e. a kilometre to a few kilometres) to regional (i.e. tens to hundreds of kilometres) scale providing information about the nature of groundwater flow systems. The groundwater hydrology activity will utilise both static (i.e. standing water level (SWL) and temporal) data publicly available via DENR (DENR 2021) as well as new data from the implementation of a hydrological monitoring program for characterising: • The depth to groundwater at given locations • Groundwater flow directions across different aquifers • The scale of groundwater flow • The hydraulic gradient between different aquifers • Spatial changes in the saturated thickness of different aquifers • Recharge to and discharge from different aquifers (see Sections 5.4 and 5.5) • The physical properties of the aquifers at different locations (see Section 5.3.3). Water level data from a combination of suitable bores identified from publicly available data as well as new bores drilled and installed by the groundwater hydrology activity will be used to map the water levels across the TLA and DCF and their equivalents. Mapping will combine static SWL data available from DENR (DENR 2021) and PWC, as well as manual SWL measurements undertaken as part of a hydrological monitoring program across different aquifers. Suitable bores for monitoring water levels will be identified as part of the regional desktop assessment (see Section 5.2). SWL measurements taken as part of hydrological monitoring will be conducted using a variety of portable submersible hand-operated electronic water level meters. The SWL at each location will be measured periodically and referenced to the Australian Height datum (AHD) from either surveyed data, LiDAR data or an existing digital elevation model (DEM). A variety of groundwater level products will be produced, to indicate the direction and scale of groundwater flow in the most promising intermediate to regional-scale aquifers. Depending on the amount, quality and location of data, products to be produced include: (i) up to 30 hydrographs, (ii) a select number of piezometric cross-sections, at the kilometre scale, and (iii) intermediate to regional- scale groundwater level maps. Groundwater level mapping will be produced using spatial analyses. These analyses will include a review of different geostatistical interpolation methods (inverse distance weighting (IDW), triangulated irregular network (TIN), spline interpolation (SI) and kriging or co-kriging) appropriate for the amount of spatial groundwater data as well as other spatial attributes of importance. Interpolations will be conducted with geographical information system (GIS) software. 5.4.2 Recharge modelling Recharge is an important component of the groundwater balance and crucial for understanding the potential availability of water from different aquifers. While recharge to the TLA and its equivalents has previously been investigated it is poorly understood for the DCF and its equivalents across other parts of the catchment. The groundwater hydrology activity will undertake a range of recharge investigations including desktop and modelling analyses as well as being derived from environmental tracer interpretation (see Section 5.4.3). Methods of regional-scale recharge estimation will include: (i) a catchment water balance analysis using remotely sensed actual evapotranspiration (ETa) data (Crosbie et al. 2015), (ii) the Australian Water Resources Assessment – Landscape (AWRA-L) model (Vaze et al. 2013), (iii) soil vegetation atmosphere transfer (SVAT) modelling using WAVES (Zhang and Dawes 1998), (iv) regionally upscaled chloride mass balance (Crosbie and Rachakonda 2021), and (v) the water table fluctuation method (Crosbie et al. 2019). Regional estimates of recharge will be constrained using point-scale estimates of recharge inferred from field data and used to evaluate recharge to aquifers in the most prospective hydrogeological units identified. Excess water The catchment water balance method relies on a water balance where net recharge can be estimated as the difference between rainfall and ETa. The non-transpired component of rainfall, also referred to as the ‘excess water’, is a combined estimate of water exported from the grid cell as either groundwater recharge or runoff. To be used as an estimate of recharge would require that the runoff component can be independently estimated. Excess water has been used as a constraint on the probabilistic estimate of recharge using the water table fluctuation method in the catchments around Darwin (Crosbie et al. 2019) and the chloride mass balance method for the Cambrian limestone aquifers (Crosbie and Rachakonda 2021). MODIS data will be used to produce scaled ETa estimates on a 250 m resolution grid using an algorithm developed by Guerschman (2009) (CMRSET) that incorporates a relationship derived from the enhanced vegetation index (EVI) and the global vegetation moisture index (GVMI). The MODIS reflectance, EVI and GVMI datasets will be sourced from the remote sensing activity; the CRMSET data will be calibrated locally to flux towers in northern Australia. Precipitation data will be sourced from the climate activity. AWRA-L The AWRA system of models was developed by CSIRO for the BoM for their Water Resource Assessments and Water Accounts (Vaze et al., 2013). The BoM provide the outputs of AWRA-L online (http://www.bom.gov.au/water/landscape/) using a single parameter set that has been calibrated at a continental scale. AWRA-L is a landscape-scale water balance model that is capable of simulating runoff, recharge, ET and soil water storage on a daily time step, on a regular grid, at a spatial resolution of 0.05 x 0.05 degrees (~5 x 5 km) (Viney et al. 2015). Within the model the recharge is the addition of water to the groundwater store after having passed beyond the root zone and through a 6 m soil column. Many of the parameters in the model are spatially variable based upon mapped vegetation, soil, terrain and geological properties. There are also 21 parameters that are calibrated to observed streamflow in unimpeded catchments. Outputs from AWRA-L will be collated, reviewed, and summarised in terms of gross recharge across the Roper catchment. WAVES The WAVES model Zhang and Dawes (1998) is a physically based model that achieves a balance in its modelling complexity between soil physics, plant physiology, energy and solute balances. WAVES has previously been used on multiple occasions to model recharge across northern Australia, including modelling of the impacts of a future climate (Crosbie et al. 2009). The WAVES model will be parameterised using pedotransfer functions based on grids of parameters generated by the digital soil mapping undertaken in the land suitability activity (cross ref SOILS). Default vegetation parameters will be assigned based on available vegetation mapping. The WAVES recharge modelling will be constrained using MODIS derived leaf area index (LAI) data and point estimates of recharge derived from field data. Up-scaled chloride mass balance The chloride mass balance (CMB) method has recently been used to estimate recharge across the Cambrian limestone aquifers (Crosbie and Rachakonda 2021), part of which are in the Roper catchment. This work will be extended to cover the entire Roper catchment. The CMB requires the chloride deposition due to rainfall (Davies and Crosbie 2018) and the chloride concentration of the groundwater. The NT government has analysed thousands of samples of groundwater for chloride concentration that can be used to estimate recharge as well as any new bores sampled as part of the groundwater sampling program (see Section 5.4.3). The recharge estimates are upscaled using regression kriging with rainfall, soil clay content and NDVI as a measure of vegetation density as covariates. The uncertainty in the probabilistic upscaled recharge estimates is then constrained using excess water at the high end and groundwater discharge as baseflow at the low end of the recharge distribution. Water table fluctuation The water table fluctuation (WTF) method of estimating recharge requires a time series of groundwater level measurements and an estimate of the specific yield at the location of the water table. A combination of existing data from monitoring bores in the Roper catchment (DENR 2021), as well as any new bores where water level loggers will be installed as part of a hydrological monitoring program could be ideal for estimating recharge using the WTF method. Any new bores where water level loggers will be installed as part of a hydrological monitoring program will be identified as part of the regional desktop assessment (see Section 5.2). The specific yield is usually poorly known and is the major source of uncertainty in this method. The uncertainty in the recharge estimates using the WTF method was recently constrained using excess water and chloride mass balance estimates of recharge in the catchments around Darwin (Crosbie et al. 2019). This same method will be applied to the suitable bores in the Roper catchment. 5.4.3 Hydrogeochemistry and environmental tracers To characterise groundwater suitability for irrigation use, as well as characterise, conceptualise and quantify groundwater flow processes, samples for chemistry and environmental tracers will collected from both groundwater and surface water and be analysed, and interpreted. Candidate bores with a suitable bore construction and an aquifer attribution to be used in a groundwater sampling program across different aquifers (TLA, DCF and their equivalents) will be identified from the regional desktop assessment (see Section 5.2). Characterising the general chemistry of different water sources (i.e. rainfall, surface water and groundwater) provides a basis for understanding the sources of salinity, acidity or alkalinity in water samples resulting from processes occurring in different components of the hydrological cycle. For example, different dissolved constituents may include salts and/or metals (ions) that may be present in water as a result of the cycling of salts with a contemporary marine origin, connate salts with an historical marine origin and salts and/or metals resulting from either terrestrial and/or hydrogeochemical weathering (rock-water interaction). Characterising the hydrogeochemical evolution of groundwater when coupled with other hydrogeological information will assist in refining the conceptual model of groundwater flow in different aquifers. The conceptual model and hydrogeological framework for different aquifers are fundamental for underpinning water balance, analytical and numerical modelling of water availability in different aquifers. In addition, the chloride concentration in groundwater and rainfall can be used as input for the CMB method (see Section 5.4.2). Environmental tracers are substances that naturally occur in the water cycle and have proved very useful for characterising groundwater systems in a variety of hydrogeological settings in northern Australia (Taylor et al. 2018a; Turnadge et al. 2018; Deslandes et al. 2019). The interpretation of environmental tracer concentrations in groundwater and surface water provides a way of tracing the evolution of groundwater flow in aquifers (i.e. sources and locations of recharge, areas of throughflow and locations and sources of discharge) including the scales, directions and rates of flow. When coupled with information including climate data, groundwater levels, aquifer type and geometry they can provide multiple lines of evidence to support a hydrogeological conceptual model. In addition to characterising and conceptualising groundwater systems, the sampling and application of multiple tracers under appropriate circumstances (i.e. using specialised sampling techniques and at groundwater infrastructure with adequate bore construction) can be used to quantify groundwater flow processes. A common application of tracers is to characterise and quantify mean residence times (MRTs) for groundwater flow processes including recharge, throughflow and discharge. Residence times for groundwater can vary significantly (i.e. a few years to tens of thousands of years) depending on the scale and physical properties of different hydrogeological units as well as changes in hydraulic gradients. The term MRTs derived from interpreting tracers has been adopted as the preferred terminology for referring to the cumulative time groundwater has spent in aquifers since the time of recharge. There are a range of different tracers available to characterise and quantify groundwater flow each providing a unique application, covering a different range in MRT and exhibiting different susceptibility to contamination, degradation and geochemical alteration. Ideal tracers are part of the water molecules itself (such as the stable hydrogen (2H) and oxygen (18O) isotopes of water and the radioactive hydrogen 3H). Or inert gases such as the noble gases (helium (He), neon (Ne), argon (Ar), krypton (Kr) and xenon (Xe) and their isotopes) because these can characterise groundwater recharge and flow processes without any geochemical alteration. Anthropogenic gases such as chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6) and bromotrifluoromethane (Halon 1301 or H-1301) can be used to characterise short mean residence times for groundwater. That is, timescales for flow ranging from years to decades which can occur in high rainfall zones like northern Australia (Taylor et al. 2018a; Turnadge et al. 2018) but careful sampling is required to avoid atmospheric contamination and they can be susceptible to degradation in certain hydrogeological settings. The concentrations of these anthropogenic gases are known from global atmospheric monitoring, they are soluble in water and represent the air–water equilibrium at the time of recharge. Tritium (3H) and carbon-14 (14C) are radioactive isotopes with half-lives of 12.32 and 5,730 years respectively (Godwin 1962; Lucas and Unterweger 2000). They are present in the atmosphere both naturally from the interaction of nitrogen with cosmic rays and by release from nuclear weapons testing in the mid-1900s (Kalin 2000). Given the respective half-lives of 3H and 14C and their known concentrations in rainfall and the atmosphere respectively, they have be used in a variety of hydrogeological systems to characterise MRTs for groundwater flow of up to about 70 years and 40,000 years respectively (Harrington and Harrington 2016a; Taylor et al. 2018a; Taylor et al. 2018b; Suckow et al. 2020). Carbon-14 though does require careful interpretation depending on the nature of the hydrogeological system due to the potential addition of dead carbon from either CO2 in the unsaturated zone or carbonate mineral weathering in the saturated zone. Helium-4 is produced by the radioactive decay of uranium and thorium in the aquifer and therefore increases with long residence times for flow. Its concentration in groundwater can vary over five orders of magnitude, which makes 4He the most sensitive tracer to detect the presence of old groundwater in an aquifer (Torgersen and Stute 2013; Taylor et al. 2018a; Deslandes et al. 2019). The groundwater hydrology activity is currently discussing the suite of tracers to be used as part of characterising aquifers of the TLA, DCF and their equivalents and it is likely to include most of the tracers mentioned above. There are numerous methods for the interpretation of environmental tracer concentrations in groundwater, from simple one-dimensional analytical solutions (Vogel 1967), via conceptional two dimensional cross sections (Harrington and Harrington 2016b; Taylor et al. 2018a) to complex numerical groundwater flow and solute transport models (Salamon et al. 2006). Depth profiles through an aquifer have shown to be extremely useful for both constraining recharge estimates but also characterising inter-aquifer connectivity (Taylor et al. 2018a; Taylor et al. 2018b; Turnadge et al. 2018), hence the nature of the drilling program described in Section 5.3. In this assessment, the hydrogeological conceptual model derived from existing data and new field investigations will dictate the interpretation approach to be used, starting with a simple model, and building in complexity as knowledge and process understanding are acquired. 5.5 Groundwater discharge Groundwater discharge is also an equally important component of the groundwater balance and crucial for understanding the potential availability of water from different aquifers. Groundwater discharge depending on the hydrogeological and climatic settings can provide water that supports a range of different ecologically and culturally significant environmental assets at the surface. For example, springs, spring-fed vegetation, phreatophytes (i.e. deep-rooted vegetation), rivers and creeks. In addition, it can be a source of recharge to other aquifers via upward or downward leakage or a source of water to the marine environment where aquifers discharge near the coast. The groundwater hydrology activity will undertake a range of field investigations to further characterise the sources, processes and locations of groundwater discharge across the TLA and DCF and their equivalents. These activities will be designed based on the current available information for: (i) GDEs, (ii) existing records of gauged spring flow and stream flow and (iii) the outputs of the existing FEFLOW models for the TLA and DCF and their equivalents (Knapton 2009b). Where appropriate there will be close links with the surface water hydrology activity (see Chapter 3). Furthermore, groundwater extraction/use will also be quantified for the TLA and DCF and their equivalents where information is available. The headwaters of the Roper River are one of the major regional groundwater discharge zones for the TLA and equivalent aquifers in the Cambrian limestone (Figure 5-1). Two regional flowpaths (the Daly and Georgina from the north and south, respectively) congregate near Mataranka (Karp 2008). Whilst major springs in Elsey National Park (Rainbow Spring and Bitter Spring) are the obvious groundwater discharge features in the landscape, groundwater discharge also occurs via numerous smaller seeps and directly through the riverbed of the Roper River and its tributaries. In addition, remote sensing estimates of evapotranspiration suggest the whole land surface within and surrounding the park is a groundwater discharge zone via tree transpiration and shallow water table evaporation. Hence, this regional discharge zone is now referred to as the ‘Mataranka Springs Complex’ to emphasise that groundwater discharge occurs throughout the landscape in various forms. Recent studies through the GBA program have also revealed the presence of geogenic helium-4 in the springs. This indicates a deeper source (or sources) of groundwater contributing to the springs as well. Knowledge gaps at present in terms of groundwater discharge to the Roper River include: • The origin and contribution of the deeper source of groundwater to the Mataranka Springs • The location of groundwater discharge zones within the river, including downstream from Mataranka • The tree species that are phreatophytes in the Mataranka Springs Complex; and, • The magnitude of tree transpiration and shallow water table evaporation within the Mataranka Springs Complex. 5.5.1 Spring water sources Environmental tracer surveys will be used to further identify the sources of water contributing to the springs. In addition to key springs, environmental tracers will be sampled in four new monitoring bores to be installed in hydrogeological units underlying the TLA and equivalents (Proterozoic sandstone and Antrim Volcanics Plateau basalt) which may be the source of the geogenic helium-4 found in the springs (see Section 5.4.3 above). Environmental tracers to be sampled in springs and groundwater are still being discussed but will ‘likely’ include: major and minor ions, 2H and 18O, 3H, 14C, methane, and noble gases (including 4He). Sampling protocols will follow procedures using specialised equipment, with care being given to collect spring and groundwater samples with minimal contact with the atmosphere (to avoid degassing losses for helium-4 and other gas tracers). Targeted springs will include Bitter Spring, Rainbow Spring, Fig Tree Spring, Botany Walk Spring and Warlock Pond Spring. 5.5.2 Seepage/baseflow to rivers and creeks About 20% of the dry season baseflow to the Roper River in the Mataranka Springs Complex is thought to discharge from riverbank seeps or directly through the riverbed (Karp 2008). However, where this discharge occurs has not been assessed. An end of dry season survey for electrical conductivity (EC), dissolved inorganic carbon (DIC) concentration, temperature and radon-222 222Rn) activity in surface water will be conducted from the junction of the Roper River with Waterhouse Creek to Red Lily Lagoon (approximately 50 km) to map potential areas of groundwater seepage. The sampling design will follow similar studies in the NT and elsewhere in northern Australia (Cook et al. 2003; Cook 2003; Harrington et al. 2011; Smerdon et al. 2012; Taylor et al. 2018a). Whilst there is evidence for some groundwater discharge farther downstream in the Roper River system (Cook 2003) this will not be investigated here. 5.5.3 Vegetation water use What tree species are phreatophytes in the Mataranka Springs Complex and the threshold in water table depth beyond which groundwater is not used by vegetation are not known. To evaluate these, five sites representing a gradient in water table depth from the surface (<2 m to >25 m) will be selected for a tree water use assessment at the end of the dry season (Lamontagne et al. 2005; Kelley et al. 2007). The end of the dry season (October – November 2021) was selected because it should represent the time of year when groundwater use is maximal. Seven potential sites have already been identified and the actual sites will be selected following a preliminary survey early in the 2021 dry season. At each site, soil at different depths and stems from three tree species will be sampled. To ensure reliable results, triplicate soil profiles will be collected at each site at approximately 0.3 to 0.5 m depth intervals until the capillary fringe is reached (if feasible). For each species, duplicate trees and duplicate stems from each tree will be collected. Predawn and midday leaf water potential will be measured on all trees sampled. Soil samples will be analysed in the laboratory for gravimetric water content and soil matric potential. In addition, groundwater samples will be collected at each site from existing observation bores. Water will be extracted from the soil and stem samples at the West Australian Biogeochemistry Centre (UWA; contact Greg Skrzypek) using cryogenic distillation. Extracted water will then be analysed on a Picarro laser absorption spectrometer at UWA. Due to WA border policies, plant materials will require prior irradiation in Queensland. In total, we will send 50 to 60 stem samples and 80 to 90 soil samples to UWA for isotopic analyses. 5.6 Assessing the opportunities and risk for future groundwater development The groundwater hydrology activity will be working closely with both DENR and CloudGMS to provide new sources of information for use in the existing integrated surface water – groundwater model of the Roper catchment. A particular focus will be on providing new information that has potential to be used in the existing FFELOW model that represents groundwater flow processes for aquifers of both the TLA and DCF. Where appropriate, hypothetical groundwater extraction scenarios will be simulated with existing models to evaluate the potential availability of water for future groundwater development. Where there is insufficient information available (i.e. no existing model) other analytical models that simulate drawdown propagation, spring flow depletion and streamflow depletion ‘may’ be considered. However, their use will be governed by whether or not they are deemed appropriate for answering questions in relation to evaluating the potential water availability for different aquifers given the amount of available hydrogeological information for a particular aquifer. In the absence of modelling, arithmetic groundwater balances will be derived where information is sufficient for the most promising aquifers identified. The potential available groundwater resource for future development will be summarised in the context of contingent allocation rules stated in the Northern Territory Water Allocation Planning Framework (DENR 2020). 5.6.1 Hypothetical groundwater extraction modelling A range of hypothetical groundwater extraction scenarios will be carefully designed in conjunction with DENR and CloudGMS hydrogeologists to evaluate the potential available water from different aquifers for beneficial use. This will only be done where hydrogeological information is deemed sufficient to support such modelling simulations. For the TLA and equivalents the existing model is already used to underpin water allocation plans and is deemed fit for purpose (Knapton 2009b; DENR 2017) However, CSIRO, DENR and CloudGMS will closely together to utilise the best available information to support further refinement of the model (i.e. new water level, geological, recharge and discharge data). Hypothetical groundwater extraction scenarios will be varied spatially and temporally and will be based on: (i) areas of soils identified as suitable for irrigated agriculture by the land suitability activity (see Chapter 4) and (ii) account for a range of crop water demands in the Roper catchment specified by the agriculture and socio-economics activity (see Chapter 8). 5.7 References Acworth, RI, Rau, GC, McCallum, AM, Andersen, MS, Cuthbert, MO (2015) Understanding connected surface-water/groundwater systems using Fourier analysis of daily and sub-daily head fluctuations. Hydrogeology Journal 23, 143-159. Boldt‐Leppin, BE, Hendry, M (2003) Application of Harmonic Analysis of Water Levels to Determine Vertical Hydraulic Conductivities in Clay‐Rich Aquitards. Groundwater 41, 514-522. Cook, P, Favreau, G, Dighton, J, Tickell, S (2003) Determining natural groundwater influx to a tropical river using radon, chlorofluorocarbons and ionic environmental tracers. Journal of Hydrology 277, 74-88. Cook, PG (2003) Inferring groundwater inflow to the Roper River (N.T.) from environmental tracers. CSIRO Land & Water. NT Government report 37/2003D. Available at https://territorystories.nt.gov.au/10070/245891. Crosbie, R, Davies, P, Harrington, N, Lamontagne, S (2015) Ground truthing groundwater-recharge estimates derived from remotely sensed evapotranspiration: a case in South Australia. Hydrogeology Journal 23, 335–350. Crosbie, R, McCallum, J, Harrington, G (2009) 'Diffuse groundwater recharge modelling across northern Australia, a report to the Australian Government from the CSIRO Northern Australia Sustainable Yields Project.' (CSIRO Water for a Healthy Country Flagship, Australia: Crosbie, RS, Doble, RC, Turnadge, C, Taylor, AR (2019) Constraining the Magnitude and Uncertainty of Specific Yield for Use in the Water Table Fluctuation Method of Estimating Recharge. 55, 7343-7361. Crosbie, RS, Rachakonda, PK (2021) Constraining probabilistic chloride mass-balance recharge estimates using baseflow and remotely sensed evapotranspiration: the Cambrian Limestone Aquifer in northern Australia. Hydrogeology Journal 29, 1399-1419. CSIRO (2009) Water in the Roper region, pp 59-120 in CSIRO (2009) Water in the Gulf of Carpentaria Drainage Division. A report to the Australian Government from the CSIRO Northern Australia Sustainable Yields Project. CSIRO Water for a Healthy Country Flagship, Australia. xl + 479pp. Available at https://www.clw.csiro.au/publications/waterforahealthycountry/nasy/documents/GulfOfCarpentaria/NASY-Roper-region-Report.pdf. Cutillo, PA, Bredehoeft, JD (2011) Estimating Aquifer Properties from the Water Level Response to Earth Tides. 49, 600-610. Davies, PJ, Crosbie, RS (2018) Mapping the spatial distribution of chloride deposition across Australia. Journal of Hydrology 561, 76-88. DENR (2017) Background Brief – Water Allocation Plan for the Tindall Limestone Aquifer, Mataranka – Daly Waters. Department of Environment and Natural Resources. Available at https://denr.nt.gov.au/__data/assets/pdf_file/0005/438008/Background-Brief-Tindall- Limestone-Aquifer-Mataranka-to-Daly-Waters.pdf. DENR (2020) Northern Territory Water Allocation Planning Framework. Department of Environment and Natural Resources. DENR, 2021. NR maps, the Department of Environment and Natural Resources web mapping tool for natural and cultural research data for the Northern Territory. Data accessed January 2021. . Deslandes, A, Gerber, C, Lamontagne, S, Wilske, C, Suckow, A (2019) Environmental Tracers in the Beetaloo Basin. Aquifer and groundwater characterization. CSIRO, Australia. Available at https://gisera.csiro.au/wp-content/uploads/2020/06/CSIRO-GISERA-W16-Task-5- environmental-tracer-study-NT-Beetaloo-final.pdf. Duffield, G (2007) AQTESOLV for Windows Version 4.5 User's Guide. HydroSOLVE, Reston, VA Godin, G (1972) 'The Analysis of Tides.' (University of Toronto Press: Toronto, Canada) Godwin, H (1962) Half-life of Radiocarbon. Nature 195, 984-984. Guerschman, JP, Van Dijk, AIJM, Mattersdorf, G, Beringer, J, Hutley, LB, Leuning, R, Pipunic, RC, Sherman, BS (2009) Scaling of potential evapotranspiration with MODIS data reproduces flux observations and catchment water balance observations across Australia. Journal of Hydrology 369, 107–119. Harrington, GA, Harrington, NM (2016a) A hydrochemical assessment of groundwater recharge and flow in the Broome Sandstone Aquifer, La Grange Area, Western Australia. A report prepared for Department of Agriculture and Food, Western Australia by Innovative Groundwater Solutions. . Available at https://researchlibrary.agric.wa.gov.au/cgi/viewcontent.cgi?article=1003&context=lr_consultrpts. Harrington, GA, Harrington, NM (2016b) A preliminary assessment of groundwater contribution to wetlands in the lower reaches of Fitzroy River catchment. A report prepared for Department of Water, Western Australia, by Innovative Groundwater Solutions. Available at https://www.agric.wa.gov.au/sites/gateway/files/Assessment%20of%20groundwater%20contribution%20to%20wetlands%20in%20the%20lower%20reaches%20of%20Fitzroy%20River%20catchment_0.pdf. Harrington, GA, Stelfox, L, Gardner, WP, Davies, P, Doble, R, Cook, PG (2011) Surface water – groundwater interactions in the lower Fitzroy River, Western Australia. CSIRO: Water for a Healthy Country National Research Flagship. 54 pp. Hartmann, T, Wenzel, H-G (1995) The HW95 tidal potential catalogue. 22, 3553-3556. Jacob, CE (1940) On the flow of water in an elastic artesian aquifer. Eos, Transactions American Geophysical Union 21, 574-586. Kalin, RM (2000) Radiocarbon dating of groundwater systems. In 'Environmental tracers in subsurface hydrology.' pp. 111-144. (Springer: Kanasewich, ER (1981) 'Time Sequence Analysis in Geophysics, 3rd ed., University of Alberta Press, Edmonton, Canada, 480p.' Karp, D (2008) Surface and groundwater interaction the Mataranka Area. Department of natural Resources, Environment, the Arts and Sport. Report No. 17/2008D, Darwin, NT. Available at https://territorystories.nt.gov.au/10070/674028/0. Kelley, G, O'Grady, AP, Hutley, LB, Eamus, D (2007) A comparison of tree water use in two contiguous vegetation communities of the seasonally dry tropics of northern Australia: the importance of site water budget to tree hydraulics %J Australian Journal of Botany. 55, 700- 708. Knapton, A (2009a) Gulf Water Study. An integrated surface – groundwater model of the Roper River Catchment, Northern Territory. Part B – MIKE11 Surfacw Water Model. Department of Natural Resources, Environment, The Arts and Sport Water Resources Branch, Tehcnical Report No. 31/2009D Available at https://territorystories.nt.gov.au/10070/580682/0/0. Knapton, A (2009b) Gulf Water Study. An integrated surface – groundwater model of the Roper River Catchment, Northern Territory. Part C – FEFLOW Groundwater Model. Department of Natural Resources, Environment, The Arts & Sport Water Resources Branch, Technical Report No. 32/2009D. Available at http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.369.7455&rep=rep1&type=pdf. Lamontagne, S, Cook, PG, O'Grady, A, Eamus, D (2005) Groundwater use by vegetation in a tropical savanna riparian zone (Daly River, Australia). Journal of Hydrology 310, 280-293. Lucas, LL, Unterweger, MP (2000) Comprehensive Review and Critical Evaluation of the Half-Life of Tritium. Journal of research of the National Institute of Standards and Technology 105, 541- 549. McMillan, TC, Andersen, MS, Timma, W, Rau, GC (in review) In-situ estimation of subsurface hydro-geomechanical properties using the groundwater response to Earth and atmospheric tides. Submitted to Water Resources Research PWC, 2021. Hydrogeological data for Ngukurr provided by Power and Water Corporation. Data accessed May 2021. Rasmussen, TC, Crawford, LA (1997) Identifying and Removing Barometric Pressure Effects in Confined and Unconfined Aquifers. 35, 502-511. Rau, GC (2018) 'PyGTide: A Python Module and Wrapper for ETERNA PREDICT to Compute Synthetic Model Tides on Earth. Institute of Applied Geosciences, Karlsruhe Institute of Technology, Karlsruhe, Germany.' Rau, GC, Cuthbert, MO, Acworth, RI, Blum, P (2020) Technical note: Disentangling the groundwater response to Earth and atmospheric tides to improve subsurface characterisation. Hydrol. Earth Syst. Sci. 24, 6033-6046. Rau, GC, Schweizer, D, Turnadge, C, Blum, P, Rasmussen, TC (2021) A new Python package to estimate hydraulic and poroelastic groundwater properties using standard pressure records. In 'EGU General Assembly 2021, 19–30 Apr 2021. Available at https://doi.org/10.5194/egusphere-egu21-4679 Renard, P, Glenz, D, Mejias, M (2009) Understanding diagnostic plots for well-test interpretation. Hydrogeology Journal 17, 589-600. Salamon, P, Fernàndez-Garcia, D, Gómez-Hernández, JJ (2006) A review and numerical assessment of the random walk particle tracking method. Journal of Contaminant Hydrology 87, 277– 305. Schweizer, D, Ried, V, Rau, GC, Tuck, JE, Stoica, P (2021) Comparing Methods and Defining Practical Requirements for Extracting Harmonic Tidal Components from Groundwater Level Measurements. Mathematical Geosciences Smerdon, BD, Gardner, WP, Harrington, GA, Tickell, SJ (2012) Identifying the contribution of regional groundwater to the baseflow of a tropical river (Daly River, Australia). Journal of Hydrology 464–465, 107–115. Suckow, A, Deslandes, A, Raiber, M, Taylor, A, Davies, P, Gerber, C, Leaney, F (2020) Reconciling contradictory environmental tracer ages in multi-tracer studies to characterize the aquifer and quantify deep groundwater flow: an example from the Hutton Sandstone, Great Artesian Basin, Australia. Hydrogeology Journal 28, 75–87. Taylor, AR, Harrington, GA, Clohessy, S, Dawes, WR, Crosbie, RS, Doble, RC, Wohling, DL, Batlle- Aguliar, J, Davies, PJ, Thomas, M, Suckow, A (2018a) Hydrogeological assessment of the Grant Group and Poole Sandstone - Fitzroy catchment, Western Australia. A technical report to the Australian Government from the CSIRO Northern Australia Water Resource Assessment, part of the National Water Infrastructure Development Fund: Water Resource Assessments. CSIRO, Australia. CSIRO. Taylor, AR, Smith, SD, Lamontagne, S, Suckow, A (2018b) Characterising alluvial aquifers in a remote ephemeral catchment (Flinders River, Queensland) using a direct push tracer approach. Journal of Hydrology 556, 600–610. Tickell, SJ, Diem Phuong Nguyen, S (2014) Pumping tests in the Northern Territory, a new spatial dataset. Northern Territory Department of Land Resource Management, Technical Report No. 4/2014D. Available at https://territorystories.nt.gov.au/10070/542791/0/0. Torgersen, T, Stute, M (2013) Helium (and other Noble Gases) as a Tool for Understanding Long Timescale Groundwater Transport. In 'Isotope Methods for Dating Old Groundwater.' (Eds A Suckow, PK Aggarwal, LJ Araguas-Araguas.) pp. 179-216. (International Atomic Energy Agency: Vienna) Turnadge, C, Crosbie, RS, Tickell, SJ, Zaar, U, Smith, SD, Dawes, WR, Davies, PJ, Harrington, GA, Taylor, AR (2018) Hydrogeological characterisation of the Mary–Wildman rivers area, Northern Territory. A technical report to the Australian Government from the CSIRO Northern Australia Water Resource Assessment, part of the National Water Infrastructure Development Fund: Water Resource Assessments. CSIRO, Australia. Vaze, J, Viney, N, Stenson, M, Renzullo, L, Van Dijk, A, Dutta, D, Crosbie, R, Lerat, J, Penton, D, Vleeshouwer, J (2013) The Australian Water Resource Assessment Modelling System (AWRA). Proceedings of the 20th International Congress on Modelling and Simulation, Adelaide, Australia. https://www.mssanz.org.au/modsim2013/L17/vaze.pdf . . In. Viney, N, Vaze, J, Crosbie, R, Wang, B, Dawes, W, Frost, A (2015) AWRA-L v5.0: Technical description of model algorithms and inputs. CSIRO, Australia. Vogel, JC (1967) Investigations of groundwater flow with radiocarbon: Isotopes in hydrology In: Proceedings for the Conference on Isotopes in Hydrology, Vienna, International Atomic Energy Agency. In. pp. 355–368. Wenzel, H-G (1996) The nanogal software: Earth tide data processing package ETERNA 3.30. Bull. Inf. Marées Terrestres 124, 9425-9439. Zaar, U (2009) Gulf Water Study. Water Resources of the Roper River Region. Northern Territory of Australia, Report 16/2009D. Available at https://denr.nt.gov.au/__data/assets/pdf_file/0006/438009/Gulf-Water-Study.pdf. Zhang, L, Dawes, WR (1998) WAVES—An Integrated Energy and Water Balance Model. CSIRO Land and Water, Canberra. Part III What are the opportunities by which water resource development may enable regional development? 6 Indigenous water values, rights, interests and development goals 6.1 Introduction The Roper River Water Resource Assessment Indigenous activity will provide an overview of key Indigenous values, rights, interests and development goals with respect to water, irrigated agriculture and other potential non-agricultural opportunities. This analysis is intended to assist, inform and underpin future discussions between developers, government and Indigenous people about particular developments and their potential positive and negative effects on Indigenous populations. The key questions that this activity will seek to address in the Roper catchment include: • What is the existing documented information pertaining to Indigenous people in the Assessment area, and to Indigenous water and development issues more generally? This will emphasise: – the historical and contemporary context for Indigenous people living in the Roper catchment – local Indigenous residence and tenure regimes in the Roper catchment – key issues in Indigenous water values, rights, interests and development goals in the Roper catchment – key issues for Indigenous people regarding water, irrigated agricultural development and other water-related development opportunities in the catchment. • How do current Traditional Owners of, and Indigenous residents in, the Roper catchment perceive water resource assessment and development? • What potential issues regarding cultural heritage arise from water resource assessment and development? • What are the key legal and policy issues with respect to Indigenous people, water and irrigated agricultural development? • What are the barriers to, and enablers of, Indigenous people participating in water resource development? • What are the barriers to, and enablers of, Indigenous people deriving social and economic benefits from water resource development? 6.2 Linkages to other Assessment activities Components of the Roper Indigenous values, rights, interests and development goals activity will have close connections with components of the agriculture and socio-economic (Chapter 7), land suitability (Chapter 4) and the ecology (Chapter 8) activities. The Indigenous activity will, through consultations with Traditional Owners and Indigenous corporations and their partners, provide a guiding framework to support the agriculture and socio-economic activity with an economic analysis of selected bush foods from the catchment. This framework will also guide the selection of bush foods for the land suitability activity. Considerations of Traditional Owners’ intellectual property and control of knowledge and potential future business opportunities are critical considerations in this work. The Indigenous activity will support the ecology activity through the collaborative identification of key natural and cultural assets of significance to Indigenous people of the Roper catchment. Indigenous knowledge will be crucial in understanding how particular assets have human ecological significance, and how they function as nodes in interconnected networks supporting biocultural diversity and sustainability. Connections with other Roper River Water Resource Assessment activities will also be identified as the study progresses. 6.3 Linkages to other research projects in the Roper catchment There are a range of other research initiatives being undertaken in the Roper catchment that provide important context for the research undertaken through the Roper River Water Resource Assessment. A key research initiative relevant to the Indigenous activity is the CSIRO Geological and Bioregional Assessment (GBA) Program in the Beetaloo Sub-basin to assess the potential environmental impacts of shale and light gas development to inform regulatory frameworks and appropriate management approaches. The Assessment results are useful to the Northern Territory Government in developing water allocation plans that are directly relevant to Indigenous communities. An understanding of the key research activities at Beetaloo Sub-basin, and the types of research results being produced, including access to fact sheets and other communication products will be important in addressing questions and directing Traditional Owners and Indigenous residents to information about the study. The Indigenous activity of the Assessment builds on previous work undertaken by Barber and Jackson (Barber and Jackson, 2011; Barber and Jackson, 2012) in the upper Roper River, on the inclusion of Indigenous knowledge in water planning. In addition, it will incorporate principles for sustainable development, barriers and enablers of participation in water planning, and whole of catchment and inter-generational impacts. 6.4 Context and consultation The Roper catchment is unique in terms of its: • governance and tenure regimes • population size and demographics • levels of pre-existing development including water-related development • existence of previous research • ongoing current and proposed future research, etc. This context makes ongoing consultation with key stakeholders crucial to determining the exact scope of the Indigenous activity. This consultation is expected to continue throughout the conduct of the research and is likely to include stakeholders from: • Australian Government • state and territory governments • local governments • Northern Land Council • regional councils • local Indigenous landholders and prescribed bodies corporate (PBC) • local Indigenous land trusts • Aboriginal Areas Protection Authority • catchment management agencies • Indigenous development agencies. 6.5 Scope Previous experience from the Flinders and Gilbert Agricultural Resource Assessment (Barber, 2013) and the Northern Australia Water Resource Assessment (NAWRA) (Barber, 2018; Barber and Woodward, 2018; Lyons and Barber, 2018) within the project team suggests that consultations about project scope and methods in the Roper catchment are likely to be iterative, and that maintaining some flexibility in project scope is important in the initial planning stages. The research will not seek to directly enable or facilitate Traditional Owner group consensus about water and irrigation development in general, or specific development scenarios considered by the Assessment. Rather, the project will focus on generating a representative set of Indigenous issues, perspectives and aspirations regarding water development that can be used as a guide and foundation for subsequent discussions between public and private developers and Indigenous interests. The evaluation and refinement of development options undertaken by the other components of the Assessment provides further shared foundations for this process. Further refinements in project scope, including jurisdictionally specific refinements, are expected to be made following further consultation. 6.6 Research ethics Prior to the commencement of the fieldwork component of the project, the research aims and proposed methods will be reviewed by the CSIRO Social Science Human Research Ethics Committee (CSSHREC). Project information sheets and a free, prior and informed consent form will also be submitted for approval by CSSHREC as part of the application. CSSHREC oversight will continue throughout the project. Following initial consultations and briefings, a one-year whole-of-Assessment research permit has been approved by the Northern Land Council. The project will make annual submissions to the Northern Land Council for a reissue of the research permit during the project life. Further consultation will be undertaken with local and subregional Indigenous organisations. Participation in the project will be entirely voluntary. Potential research participants will be provided with clear explanations of the research process and outcomes through a combination of telephone, face-to-face, and written contact prior to them making any decision to participate. Wherever practicable, research participants will be afforded an extended period (of 1 month or more) after first contact by research staff to allow time for further consideration and consultation before making a decision to participate. During initial contact, the project information sheets and the written consent form will be supplied. After this process had taken place, verbal consent will be sought and then confirmed through the participant signing the consent form. These forms are to be retained by CSIRO staff in a secure location. Based on experience of past projects, it is expected that rather than participants being individually identified, comments that appear in any report will be identified through a more general group identifier. This retains anonymity but also provides a level of geographic specificity. 6.7 Methods 6.7.1 Review of existing information The review of existing documented information will encompass: • the historical and contemporary context for Indigenous people living in the Roper catchment • local Indigenous residence and tenure regimes • key issues in Indigenous water values, rights, interests and aspirations • key issues for Indigenous people regarding water, irrigated agricultural development and its interactions with other water-related development. Relevant supporting data generated by other activities (for example, ecological data with biocultural implications) will also be integrated with the review. 6.7.2 Fieldwork and direct consultation The fieldwork will emphasise direct consultation with Traditional Owners of, and Indigenous residents in, the Roper catchment through a combination of: • telephone and face-to-face interviews • group meetings and workshops • trips to key locations • other research methods developed in consultation with local and regional stakeholders. Local Indigenous organisations and individuals in each jurisdiction will influence the degree to which particular methods (e.g. individual interviews) are positioned with respect to other options (large workshops and groups). Participants will be identified through a ‘snowball’ method of iterative consultation with key local and regional Indigenous organisations – Northern Land Council, local group-based Indigenous corporations, and catchment management agencies. The objectives and intended methods of the research will be explained, copies of project information and consent forms provided, and further direction taken about people and organisations who should be contacted in the preliminary scoping and identification stage of the Assessment. Key organisations and individuals nominated by these Indigenous organisations will then be approached for further consultation during planned field trips. 6.7.3 Cultural heritage assessment The Assessment will provide regionalised, landscape-scale desktop information about cultural heritage based on information agreed with the Aboriginal Areas Protection Authority. It will also contain general commentary, drawn from past work in the Northern Australia Water Resource Assessment (NAWRA) project, about the cultural heritage values and issues that are potentially significant in future water resource development. Particular attention will be paid to future water storage options identified through Assessment research. 6.7.4 Legal and policy analysis This component of the activity will provide a desktop description of current legislative and policy requirements relevant to the inclusion of Indigenous interests in the Assessment and development of water resources in the Northern Territory (including water rights, cultural heritage, Aboriginal freehold and native title). It will also identify key legislative and policy challenges to, and opportunities for, recognising and valuing Indigenous interests associated with water resources in the Northern Territory. The analysis will focus on rights and interests recognised in the Australian Commonwealth and Northern Territory legal systems including recent developments designed to better accommodate Indigenous water values and rights in the Northern Territory Government’s allocation planning processes. The analysis will also note instances where Indigenous customary laws and cultural understandings of water are not currently recognised by the legal and regulatory system. 6.8 Data analysis and preliminary dissemination The data from the literature and interviews will be iteratively analysed using NVivo qualitative analytical software to identify major themes and key findings. Key information and research participant comments from the interviews will be identified, extracted and then formally checked with the respective research participants as both an accurate reflection of their views and as able to be used in further analysis and public presentation. The resulting information and analysis will then be combined into a draft research report. This will be disseminated to local Indigenous research participants and key Indigenous stakeholders for further comment, correction and confirmation. The report will be augmented by further presentations to group meetings. The resulting feedback will be incorporated into a revised draft report, which will then be subjected to scientific peer review and further community comment prior to finalisation. 6.9 Staff and collaboration The Indigenous activity team includes Peci Lyons, the project lead, and Marcus Barber as project advisor. Peci Lyons led the Mitchell catchment Indigenous sub-project of the NAWRA project and Marcus Barber was the overall project lead for all three catchments of NAWRA. Together they bring over 20 years of research experience on Indigenous water issues in northern Australia. Peci Lyons will coordinate the activity and its articulation with other Assessment activities, and undertake primary fieldwork. Additional CSIRO and non-CSIRO staff may be added on an as-needs basis. 6.10 Project governance and oversight Project governance and oversight containing Indigenous representation will be established at the ‘whole-of-project’ level in consultation with the Northern Land Council. Specific governance and oversight for the Indigenous activity will be provided through regular reporting to the relevant regional councils of the Northern Land Council. Further reporting to the Northern Land Council Executive and Full Council will be at the direction of the Northern Land Council. 6.11 References Barber M (2013) Indigenous water values, rights and interests in the Flinders and Gilbert catchments. A technical report to the Australian Government from the CSIRO Flinders and Gilbert Agricultural Resource Assessment, part of the North Queensland Irrigated Agriculture Strategy. CSIRO Water for a Healthy Country and Sustainable Agriculture flagships, Australia. Barber M (2018) Indigenous water values, rights, interests and development objectives in the Darwin catchments. A technical report to the Australian Government from the CSIRO Northern Australia Water Resource Assessment, part of the National Water Infrastructure Development Fund: Water Resource Assessments, Australia. Barber M and Jackson S (2011) Indigenous water values and water planning in the upper Roper River, Northern Territory. CSIRO, Darwin. Barber M and Jackson S (2012) Indigenous water management and water planning in the upper Roper River, Northern Territory: history and implications for contemporary water planning. CSIRO, Darwin. Barber M and Woodward E (2018) Indigenous water values, rights, interests and development objectives in the Fitzroy catchment. A technical report to the Australian Government from the CSIRO Northern Australia Water Resource Assessment, part of the National Water Infrastructure Development Fund: Water Resource Assessments, Australia. Lyons I and Barber M (2018) Indigenous water values, rights, interests and development objectives in the Mitchell catchment. A technical report to the Australian Government from the CSIRO Northern Australia Water Resource Assessment, part of the National Water Infrastructure Development Fund: Water Resource Assessments, Australia. 7 Surface water storage The purpose of the surface water storage activity is to provide a comprehensive overview of the different surface water storage options in the Roper catchment, to enable decision makers to take a long-term view of water resource development and to inform future allocation decisions. In this chapter, methods are described by which different surface water storage options will be assessed in the Assessment. The key questions that this activity seeks to address in the Roper catchment include: • Where are the highest yielding and most geologically suitable farm-scale and large dam sites? • How much water could dams yield and at what cost? • Would the reservoir inundate endangered ecosystems? • After how many years would large dam(s) infill with sediment? • What is the opportunity for storing water in offstream farm-scale water storages, such as ringtanks? • How much water is contained in naturally occurring wetlands and waterholes? • Where are the best opportunities for hydro-electric power generation? This chapter consists of two parts. The first part details the methods that will be undertaken as part of a scoping-level assessment and pre-feasibility assessment of large (i.e. >10 GL) instream and offstream storages. The second part examines opportunities for farm-scale water storage structures (i.e. <10 GL), such as hillside dams and ringtanks. 7.1 Introduction In a highly seasonal climate such as the Roper catchment, and in the absence of a suitable groundwater resource, industries that require year-round use of water will need to invest in surface water storage infrastructure. Currently no major surface water storages exist in the Roper catchment, nor have any previous studies on surface water storage in the Roper catchment been identified. 7.2 Large instream and offstream storages This section describes the methods by which potential dam sites will be selected (Section 7.2.1) for pre-feasibility analysis (Section 7.2.2). Section 7.2.4 describes the additional analysis that is intended for the short-listed sites. 7.2.1 Initial scoping-level assessment using the DamSite model Instream storages are highly contentious because they can affect existing environmental, cultural and recreational values. The process by which large dams are selected for investigation has often been unclear or seemingly subjective, and the decision-making process is not always transparent to all stakeholders. This section presents an open and transparent method by which sites will be selected for a pre-feasibility analysis. The first step involves running the DamSite model over the entire catchment to identify those locations in the catchment likely to be more promising for large instream dams, farm-scale gully dams and offstream storages. DamSite model The DamSite model (Read et al., 2012; Petheram et al., 2013) uses a digital elevation model (DEM) to assess all locations on a river network and test simulated dam walls of varying heights, to produce a comprehensive dataset of sites with relevant attributes, including catchment area, runoff, reservoir volume, reservoir surface area, dam height, dam width and dam face area. Saddle dams are included in the Assessment if required by the terrain. This dataset will include an exhaustive set of potential dam locations – more than 100,000 potential sites in each catchment (based on previous experience with DamSite). These sites are then filtered to identify approximately 5000 of the most suitable sites, using a combination of criteria including yield, construction cost, and yield per dollar construction cost. Yield is initially calculated at every location and every metre increment height using the Gould– Dincer Gamma method, and then refined for the subset of around 5000 sites using a behaviour analysis model. Construction cost is calculated using a cost algorithm that serves to penalise higher and longer dam walls. The cost algorithm will be refined as part of the Assessment to improve its accuracy. Key input data to the DamSite model are the SRTM DEM-H (Shuttle Radar Topography Mission; the best available DEM across the Roper catchment), gridded climate data and gridded runoff data from the surface water hydrology activity. 7.2.2 Pre-feasibility analysis The pre-feasibility analysis is largely a detailed desktop analysis of a selection (approximately six) of the more promising potential dam sites in the Roper catchment. It involves a comprehensive review of past studies, a reassessment of each site using a consistent set of methods and models, and a site investigation by an experienced infrastructure planner and engineering geologist. Each site will be evaluated and the results reported against a consistent set of criteria. The criteria and the methods by which each criteria will be evaluated are described in Table 7-1. Table 7-1 Proposed methods for assessing potential dam sites in the Roper catchment For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au 7.2.3 Assessment of system yield The system yield from of two or more reservoirs in series will be investigated as part of the river system scenario modelling. 7.2.4 Short-listed dam sites Based on the pre-feasibility analysis, a short list will be compiled of approximately three of the more promising dam sites in the Roper catchment. Short-listed sites will be primarily selected based on topography of the dam axis, geological conditions, proximity to suitable soils, water yield, and ecological and cultural considerations. Additional studies undertaken for the short-listed dam sites will include a flood design study, a detailed cost estimate and a desktop cultural heritage assessment. High-resolution data will be acquired for the short-listed dam sites using laser altimetry or photogrammetry methods. For any of these options to advance to construction, a feasibility analysis would need to be undertaken, which would involve several iterations of detailed (and expensive) studies, and ultimately development of a business case. Studies at this level of detail are beyond the scope of the current regional-scale resource assessment. 7.3 Farm-scale instream and offstream storages This section describes the methods for assessing the opportunities for farm-scale instream and offstream water storage structures (i.e. <10 GL). Instream storages include gully dams and hillside dams, while offstream water storage facilities can take the form of ringtanks, turkey nest tanks and excavated tanks (described in more detail in Table 7-2). Weirs can also be used in conjunction with some offstream water storages, where the weir is used to raise the upstream water level to allow diversion into an offstream storage or the creation of a pumping pool. The most suitable type of farm-scale water storage depends on a number of factors, including topography, the availability of suitable soils, excavation costs and the source of water (e.g. groundwater or surface water pumping, flood harvesting). Table 7-2 Types of offstream water storages (Lewis, 2002) For more information on this figure, table or equation please contact CSIRO on enquiries@csiro.au The following analysis will be undertaken to assess the opportunities for farm-scale water storages in the Roper catchment: • The soil attribute grids (to a depth of 1.5 m) generated as part of the land suitability activity and locally specific rules will be used to identify those parts of the Assessment area that are more and less suitable for farm-scale water storages. The Assessment will draw on bore lithology logs, expert and local knowledge, and electromagnetic data to make assessments below 1.5 m. • The DamSite model will be used to identify those parts of the Assessment area that are likely to be hydrologically and topographically favourable for instream farm dams (e.g. hillside dams). • Likely physical constraints to water pumping in key river reaches (i.e. minimum pumping thresholds) will be estimated. • Spatial analysis, remotely sensed imagery and local engineering expertise will be used to identify those parts of the landscape that are likely to be more suitable for diversion structures. • Over those sections of river reach where there are opportunities to impound water running down flood-outs, a higher-resolution DEM will be obtained using laser altimetry flown by helicopter; the reliability with which the flood-outs run will be estimated using a one- dimensional hydraulic model. Acquisition of higher-resolution DEM cross-sections will primarily occur in those areas identified by the interim land suitability maps as having large continuous areas of land suitable for irrigated agriculture. In assessing regional-scale economics of water harvesting schemes, local variations in scale and site-specific nuances can present challenges. These can result in considerably different construction and ongoing operational costs from one site to another (e.g. costs for different amounts of diesel required for pumping, removal of sediment deposited in diversion channels, replacement of worn and damaged equipment). Hence, operationally, each site would require its own specifically tailored engineering design. As a result, the Assessment will not produce individual engineering designs for water harvesting infrastructure for each landholder in the Assessment area; this is beyond the scope and resources of the Assessment. Besides, most landholders will have observed the way in which water moves across their land and will have given considerable thought to their most suitable water harvesting configurations. However, the Assessment will provide some overarching principles that could be used by individual landholders in designing, siting and costing water harvesting infrastructure in the Roper catchment, as well as a relevant list of references on farm dam planning, construction and maintenance. 7.4 References Lewis B (2002) Farm dams: planning, construction and maintenance. Landlinks, Collingwood, Victoria. Liu WT, Katsaros KB and Businger JA (1979) Bulk parameterization of air-sea exchanges of heat and water vapor including the molecular constraints at the interface. Journal of the Atmospheric Sciences 36(9), 1722–1735. Morton FI (1983) Operational estimates of lake evaporation. Journal of Hydrology 66(1–4), 77– 100. Petheram C, Rogers L, Eades G, Marvanek S, Gallant J, Read A, Sherman B, Yang A, Waltham N, McIntyreTamwoy S, Burrows D, Kim S, Podger S, Tomkins K, Poulton P, Holz L, Bird M, Atkinson F, Gallant S and Kehoe M (2013) Assessment of surface water storage options in the Flinders and Gilbert catchments. A technical report to the Australian Government from the CSIRO Flinders and Gilbert Agricultural Resource Assessment, part of the North Queensland Irrigated Agriculture Strategy. CSIRO Water for a Healthy Country and Sustainable Agriculture flagships, Australia. Read AM, Gallant JC and Petheram C (2012) DamSite: an automated method for the regional scale identification of dam wall locations. 34th Hydrology and Water Resources Symposium, Sydney, Australia, 19–22 November 2012. Engineers Australia, Canberra. 8 Agriculture and socio-economics The approach used to analyse the viability of agricultural development options in the Roper catchment will draw on similar recent technical assessments (Petheram et al., 2013a; Petheram et al., 2013b; Ash et al., 2014; Ash et al., 2017; Ash et al., 2018a; Ash et al, 2018b; Stokes et al., 2017). The key question that this activity seeks to address in the Roper catchment is: • What farming options are likely to be able to cover the costs of new development(s) and/or deliver the most economic benefit to the Roper catchment region? The agriculture and socio-economics activity will take a multi-scale approach (Figure 8-1), from farm to regional scale. Methods for key components of the activity are outlined below and expanded in this chapter. • The emphasis of the ‘farm-scale component’ will be a bottom-up analysis, working from the biophysical and management determinants of crop productivity to indicative farm gross margins that could be achieved for a range of cropping and fodder options. • The ‘scheme-scale component’ will initially take a generic top-down approach, working backwards from the costs of new developments to the farm gross margins that would have to be sustained to cover those costs. • The ‘regional-scale component’ will look at the knock-on economic impacts that could occur if new agricultural areas were developed in the Roper catchment. For more information on this figure or equation or table, please contact CSIRO on enquiries@csiro.au StakeholdersOpportunitiesto be evaluatedFarm-scale: bottom-up GMCrop physiology, Models, Gross marginScheme-scale: top-down GMGM required to pay for infrastructureRegional-scale: input–outputKnock-on regional economic impactSoilsWaterClimateCostsManagementVIABLE ? Figure 8-1 Overview of the approach for assessing the agricultural and economic viability of agricultural development options in the Roper catchment Note: In the figure, GM = gross margin. The combined analytical framework will also allow fully integrated cost–benefit analysis of specific case studies, based on farm-scale analyses and information from assessments of land and water resources and associated surface water storage options. Rather than being prescriptive about cropping systems for particular locations, the aim is to provide insights on the issues and opportunities associated with developing integrated cropping or crop–livestock systems, which will be illustrated with a range of contrasting prospective cropping options. The set of crops that will be considered in the analyses will be determined as the project progresses and will rely heavily on the surface water hydrology (Chapter 3), surface water storage (Chapter 7) and land suitability (Chapter 4) activities, and stakeholder input (including the Indigenous activity, Chapter 6) to define the scale, location, costs and nature of ‘development opportunities’. 8.1 Farm-scale analyses 8.1.1 Overview Assessing the viability of different farming options requires bringing together information and knowledge on climate, soils, water resources, agronomy, natural resource management, pests and diseases, and farm economics and using analytical tools to provide quantitative outputs for interpretation. This information will be used in the Assessment to drive an analysis of the type of cropping systems and/or crop–livestock systems to deliver the most favourable yields and farm gross margins, given the constraints of soils, environment, climate, and supply and reliability of irrigation resources. The approach requires an understanding of crop physiology and the sensitivity of crop growth to local climate as a precursor to individual crop and fodder assessment, using modelling, industry best practice and expert knowledge, as no field work is planned for model validation. Climate (temperature, rainfall and radiation) influences crop type, optimal growing windows and crop management not only in the context of individual crop needs but also in terms of how cropping and forage systems can be constructed to make the most effective use of available resources, such as water. Past publications and expert input will be sought and reviewed, covering cropping and livestock experience (either actual (trial, commercial) or desktop). Expert knowledge and local industry experience from existing agriculture in the Katherine and Douglas Daly regions will be particularly important in the Roper catchment due to the lack of broadacre cropping or horticulture experience in the catchment. 8.1.2 Agricultural viability Crop and forage modelling and analysis The cropping systems analysis will depend on having estimates of crop, forage and livestock production for individual components of the system and will require data and outputs from the land suitability and surface water storage activities. For the Roper catchment, a range of crops and forages are potentially suitable, including broadacre crops (e.g. sorghum, pulses), horticultural crops (e.g. mangoes, melons), root crops (e.g. peanuts, cassava), forages (e.g. sorghum, lablab) and industrial crops (e.g. cotton, industrial hemp). Estimating crop and forage production relies on highly parameterised simulation models such as the Agricultural Production Systems sIMulator (APSIM) and the Crop Livestock Enterprise Model (CLEM). Initial estimates of production will be based on generic soils selected to match as closely as possible existing soils information in the Assessment area, but these will be adjusted as new information becomes available. The modelling work also provides estimates of water used for different crops and forages. Ultimately, this will link to water requirements for cropping systems, with feedback to water resource requirements, availability and reliability. Losses of water from irrigation land may affect water quality in streams and aquifers. It will be important to link with the ecology activity (Chapter 9) to consider possible off-site impacts. The influence of irrigated agriculture on Indigenous water values, rights and development goals may also need to be considered. APSIM may not have the capability to simulate all the development options of interest in the Roper catchment, so a pluralistic approach will be taken, using simulation models, industry data, best practice and expert knowledge. For crops such as some cucurbits, tree crops, vegetables, some fodder or pastures and industrial crops such as hemp, expert and local experience from existing agricultural regions in northern Australia will be used to develop an assessment of production potential and water use. For some of these cropping systems, simple day degree models exist that have been designed to estimate harvest date and potential yield. These simple models will be compared with available data in each catchment to determine their utility. Where existing cropping systems (e.g. mango and melon) operate in north Queensland, Western Australia and Northern Territory, production and water use data will be collected from the existing farming systems to inform the Assessment. Crop calendars will be developed for each crop and forage assessed. Agricultural Production Systems sIMulator APSIM is a modelling framework that has been developed to simulate biophysical process in farming systems (Holzworth et al., 2014) and has been used for a broad range of applications, including on-farm decision making, seasonal climate forecasting, risk assessment for government policy making, and evaluating changes to agronomic practices (Keating et al., 2003; Verburg et al., 2003). It has demonstrated utility in predicting performance of commercial crops, provided that soil properties are well characterised (Carberry et al., 2009). Validated crop models have been used in previous assessments of cropping potential for a range of prospective crops in northern Australia (Carberry et al., 1991; Pearson and Langridge, 2008; Webster et al., 2013; Yeates, 2013; Ash et al., 2017). The APSIM simulation framework has been extensively employed in earlier agricultural assessments in northern Australia (Northern Australia Water Resource Assessment (NAWRA), Flinders and Gilbert Agricultural Resource Assessment, Northern Australia Food and Fibre Supply Chains Study). Although the focus of this work will be on fully irrigated crop and forage production, opportunistic dryland and supplementary irrigation options will be considered. Crop Livestock Enterprise Model CLEM will be used to explore the opportunities for irrigated forages and crops to increase productivity in the beef industry and to provide different market opportunities beyond live export. CLEM is a whole-farm-scale dynamic simulation model that mimics the response over time of a beef cattle enterprise with a specified herd structure of age and sex classes. It integrates livestock, pasture and forage crop production with labour and land resource requirements and availability; accounts for component revenue and cost streams; and provides estimates of the expected environmental consequences (e.g. land condition, soil erosion) of various management options. CLEM was developed from the North Australian Beef Systems Analyser (NABSA) (Ash et al., 2015) that has been utilised in previous studies in northern Australia. Farm gross margins and overheads The farm gross margin is the difference between the revenue received for the harvested produce and the variable costs incurred in growing the crop. Gross margin templates will be set up for each crop to calculate variable costs and revenue under a range of conditions and locations in the Roper catchment, based on similar work that was done in NAWRA. Farm overheads, the fixed costs that a farm incurs each year even if no crop were planted, will be calculated for a generic broadacre farm. Annual net farm revenue is the difference between the farm gross margin and the overhead costs. 8.2 Scheme-scale analyses Scheme financial evaluations will use industry standard cost–benefit methods (OBPR, 2016), based on a discounted cashflow framework, to evaluate the commercial viability of irrigation developments. The framework, detailed in the NAWRA socio-economic technical report (Stokes et al., 2017), provides a purely financial evaluation of the conditions that would be required to produce an acceptable return from an investor’s perspective. Initially, a generic ‘top-down’ approach will be taken, working backwards from the costs of developing a new irrigation scheme to determine the farm gross margins that would be required to generate an acceptable rate of return on the investment. This will be compared against the ‘bottom-up’ indicative farm gross margins from the farm-scale analyses to identify which crop options could be potentially viable. A discounted cashflow analysis considers the lifetime of costs and benefits following capital investment in a new project. Costs and benefits that occur at different times are expressed in constant real dollars, with a discount rate applied to streams of costs and benefits. Costs included will be the capital costs of developing the land and water resources, and the ongoing maintenance and operating costs. Cohorts of infrastructure assets will be tracked according their lifespans to account for replacement and residual values over the evaluation period. Net farm revenue each year will be calculated by subtracting fixed overhead costs from the gross margin. Additional analyses will quantify the effects of various risks and risk-mitigation measures on the farm gross margins that would be required for a scheme to break even. 8.3 Regional economic impacts The full, catchment-wide impact of the economic stimulus provided by an irrigated development extends far beyond the impact on those businesses and workers directly involved both in the short term (construction phase) and longer term (operational phase). There are knock-on stimulus effects to other businesses in the region whose goods and services are purchased to support the new economic activity, and household incomes increase where local residents are employed (as a consequence of the direct and/or production-induced business stimuli) leading to increases in household expenditure that further stimulates the regional economy. The combined regional economic benefit would depend on the scale of the development, the type of agriculture that is established, and how much spending from the increased economic activities occurs within the region. The size of the impact on the Roper catchment regional economy will be estimated using regional economic multipliers (derived from input–output tables that summarise expenditure flows between industry sectors and households within the Northern Territory region (Murti, 2001)), following the approach used in NAWRA (Stokes et al., 2017). 8.4 References Ash A, Gleeson T, Cui H, Hall M, Heyhoe E, Higgins A, Hopwood G, MacLeod N, Paini D, Pant H, Poulton P, Prestwidge D, Webster T and Wilson P (2014) Northern Australia: food and fibre supply chains study project report. CSIRO & ABARES, Australia. Ash AJ, Hunt L, McDonald C, Scanlan J, Bell L, Cowley R, Watson I, McIvor J and Macleod N (2015) Boosting the productivity and profitability of northern Australian beef enterprises: exploring innovation options using simulation modelling and systems analysis. Agricultural Systems 139, 50–65. Ash A, Gleeson T, Hall M, Higgins A, Hopwood G, MacLeod N, Paini D, Poulton P, Prestwidge D, Webster T and Wilson P (2017) Irrigated agricultural development in northern Australia: value-chain challenges and opportunities. Agricultural Systems 155,116–125. Ash A, Bristow M, Laing A, MacLeod N, Niscioli A, Paini D, Palmer J, Poulton P, Prestwidge D, Stokes C, Watson I, Webster T and Yeates S (2018a) Agricultural viability: Darwin catchments. A technical report from the CSIRO Northern Australia Water Resource Assessment, part of the National Water Infrastructure Development Fund: Water Resource Assessments, Australia. Ash A, Cossart R, Ham, C, Laing A, MacLeod N, Paini D, Palmer J, Poulton P, Prestwidge D, Stokes C, Watson I, Webster T and Yeates S (2018b) Agricultural viability: Fitzroy catchment. A technical report from the CSIRO Northern Australia Water Resource Assessment, part of the National Water Infrastructure Development Fund: Water Resource Assessments, Australia. Carberry PS, Cogle AL and McCown RL (1991) Future prospects for cropping in the semi-arid tropics of north Queensland. Land Management Research, CSIRO Division of Tropical Crops and Pastures, St Lucia, Queensland. Carberry PS, Hochman Z, Hunt JR, Dalgleish NP, McCown RL, Whish JPM, Robertson MJ, Foale MA, Poulton PL and Van Rees H (2009) Re-inventing model-based decision support with Australian dryland farmers. 3. Relevance of APSIM to commercial crops. Crop & Pasture Science 60, 1044–1056. Holzworth DP, Huth NI, deVoil PG, Zurcher EJ, Herrmann NI, McLean G, Chenu K, van Oosterom E, Snow V, Murphy C, Moore AD, Brown H, Whish JPM, Verrall S, Fainges J, Bell LW, Peake AS, Poulton PL, Hochman Z, Thorburn PJ, Gaydon DS, Dalgliesh NP, Rodriguez D, Cox H, Chapman S, Doherty A, Teixeira E, Sharp J, Cichota R, Vogeler I, Li FY, Wang E, Hammer GL, Robertson MJ, Dimes J, Carberry PS, Hargreaves JNG, MacLeod N, McDonald C, Harsdorf J, Wedgwood S and Keating BA (2014) APSIM − evolution towards a new generation of agricultural systems simulation. Environmental Modelling & Software 62, 327–350. Keating BA, Carberry PS, Hammer GL, Probert ME, Robertson MJ, Holzworth D, Huth NI, Hargreaves JNG, Meinke H, Hochman Z, McLean G, Verburg K, Snow V, Dimes JP, Silburn M, Wang E, Brown S, Bristow KL, Asseng S, Chapman S, McCown RL, Freebairn DM and Smith CJ (2003) An overview of APSIM, a model designed for farming systems simulation. European Journal of Agronomy 18: 267–288. Murti S (2001) Input-output multipliers for the Northern Territory 1997–1998. Office of Resource Development, Darwin, NT. OPBR (2016). Cost-benefit analysis: guidance note. Office of Best Practice Regulation. Department of Prime Minister and Cabinet, Canberra. Pearson L and Langridge J (2008) Climate change vulnerability assessment: review of agricultural productivity. CSIRO Climate Adaptation Flagship Working paper No.1. Viewed 2/12/2019, https://doi.org/10.4225/08/5856d20d07ed3 . Petheram C, Watson I and Stone P (eds) (2013a) Agricultural resource assessment for the Flinders catchment. A report to the Australian Government from the CSIRO Flinders and Gilbert Agricultural Resource Assessment, part of the North Queensland Irrigated Agriculture Strategy. CSIRO Water for a Healthy Country and Sustainable Agriculture flagships, Australia. Petheram C, Watson I and Stone P (eds) (2013b) Agricultural resource assessment for the Gilbert catchment. A report to the Australian Government from the CSIRO Flinders and Gilbert Agricultural Resource Assessment, part of the North Queensland Irrigated Agriculture Strategy. CSIRO Water for a Healthy Country and Sustainable Agriculture flagships, Australia. Stokes C, Addison J, Macintosh A, Jarvis D, Higgins A, Doshi A, Waschka M, Jones J, Wood A, Horner N, Barber M, Bruce C, Austin J and Lau J (2017) Costs, benefits, institutional and social considerations for irrigation development. A technical report to the Australian Government from the CSIRO Northern Australia Water Resource Assessment, part of the National Water Infrastructure Development Fund: Water Resource Assessments, Australia. Verburg K, Bond WJ and Smith CJ (2003) Use of APSIM to simulate water balances of dryland farming systems in south eastern Australia. CSIRO Land and Water, Canberra. Webster T, Poulton P, Yeates SJ, Cocks B, Hornbuckle J, Gentle J, Brennan McKellar L, Mayberry D, Jones D and Wixon A (2013) Agricultural productivity in the Flinders and Gilbert catchments. A technical report to the Australian Government from the CSIRO Flinders and Gilbert Agricultural Resource Assessment, part of the North Queensland Irrigated Agriculture Strategy. CSIRO Water for a Healthy Country and Sustainable Agriculture flagships, Australia. Yeates SJ, Strickland GR and Grundy PR (2013) Can sustainable cotton production systems be developed for tropical northern Australia? Crop & Pasture Science 64, 1127–1140. Part IV What are the likely risks and opportunities to the natural environment due to changes in the river flow regime as a result of water resource development? 9 Ecology River flow regimes are regarded as a primary driver of riverine and floodplain wetland ecology (Bunn, 2002 #318 ; Junk, 1989 #822 ; Poff, 2010 #4267 ). Water resource development has the potential to change the flow regime leading to changes in important flow attributes such as the magnitude, timing, duration and rate of change of flow events to which the ecosystem is adapted. These changes create new conditions, thereby resulting in potential ecological changes and consequences for the biota and ecosystem processes of a catchment (Poff, 1997 #420 ). The ecology activity seeks to determine the relative trade-offs between different water resource development scenarios in the Roper catchment using a set of prioritised water-dependent assets. The analysis focuses on understanding outcomes resulting from changes in the flow regime. The key questions that this activity seeks to address in the Roper catchment include: • What is the main environmental context of the Roper catchment that could influence water resource development? • What are the key environmental drivers and stressors that are currently occurring or likely to occur in the Roper catchment (including key supporting and threatening processes such as invasive species, water quality and habitat changes)? • What are the known linkages between flow and ecology? • What are the key ecological trade-offs between different water resource developments considering potential changes in flow? 9.1 Regional overview The Roper River is a large perennial flowing river with one of the largest catchment areas draining into the western gulf (82,000 km2) (Faulks, 2001 #2 ). Due to the very flat topography of the upper catchment, the river braids into smaller channels that provide a diverse habitat structure (CSIRO, 2009 #4 ). The wet-dry tropical climate of the catchment results in highly seasonal flow, with high flows occurring during the wet season. During the dry season river flows are reduced and much of the streams in the catchment recede to pools. Streams and waterholes that persist provide critical refuge habitat for many species (Barber, 2011 #5 ) where dry-season flow is largely supported by the groundwater discharge from the Tindall Limestone Aquifer of the Daly Basin. Important springs between Mataranka and the Red Lily Lagoon provide habitat and enrich the river flow by seepage through the river banks (Northern Territory Government, 2010 #9 ). About 2% of the Roper catchment is under protection. There are two national parks (Elsey and Limmen), one Indigenous Protected Area (South East Arnhem Land Indigenous Protected Area), a private nature reserve (Wongalara Sanctuary) and a management area (St Vidgeon). The catchment contains two wetlands of national significance (Directory of Important Wetlands in Australia (DIWA) listed), being the Limmen Bight (Port Roper) Tidal Wetlands System and the Mataranka Thermal Pool (Department of the Environment, 2010 #10 ). The Limmen Bight Tidal Wetlands System is the second-largest area of saline coastal flats in the Northern Territory (185,000 ha), forming one of the most important habitat systems of tidal wetlands (intertidal mud flats, saline coastal flats and estuaries) for migratory shorebirds in the Northern Territory (Department of the Environment, 2010 #10 ). This wetland system provides important habitat for species listed in the Environment Protection and Biodiversity Conservation Act 1999 (Cth) (EPBC Act) including the northern Siberian bar-tailed godwit (Limosa lapponica menzbieri; critically endangered), eastern curlew (Numenius madagascariensis; critically endangered) and the Australian painted snipe (Rostratula australis; endangered). Mataranka Thermal Pool in the upper catchment is maintained by permanent thermal springs located within Elsey National Park in an area of less than 10 ha (Department of the Environment, 2010 #10 ). Listed species in this national park include the red goshawk (Erythrotriorchis radiatus; vulnerable) and the Mertens’ water monitor (Varanus mertensi; vulnerable for the Northern Territory). Overall the Roper catchment contains a high diversity of flora and fauna including about 270 vertebrate species (Dasgupta, 2019 #14 ). Freshwater crocodiles (Crocodylus johnstoni) are very common within the Roper River and its tributaries (CCNT, 1994 #12 ), while the saltwater crocodile (C. porosus) occurs upstream along the Roper River to Elsey Station (Griffiths, 1997 #11 ). Extensive seagrass beds in nearby coastal Gulf of Carpentaria waters are an important feeding area for dugongs (Dugong dugon) and turtles and support a major juvenile habitat for tiger and endeavour prawns (Penaeus spp. and Metapenaeus spp.) (Department of the Environment, 2010 #10 , Kenyon et al. 1999). Additionally, the near-coastal waters and estuaries support six listed species of marine turtles and a major commercial barramundi (Lates calcarifer) fishery, while harvest of mud crabs (mainly Scylla serrata) also occurs at Port Roper and along nearby coasts (Northern Territory Government, 2019 #15 ). Only a relatively small proportion of the catchment is occupied by riparian habitats. These habitats however, frequently have a higher abundance and species richness compared to surrounding habitats (Lynch R.J., 1999 #13 ). The riparian vegetation mainly consists of Livistona mariae subsp. rigida, although Pandanus spp. and Melaleuca spp. also occur. The distribution of L. mariae palm community is very restricted in northern Australia and, as such, is considered a special community (Faulks, 2001 #2 ). This vegetation community contains a rich frog fauna and the little red flying-fox (Pteropus scapulatus) often use it as a maternity colony. The gulf snapping turtle (Elseya lavarackorum), which is listed as endangered in the EPBC Act, has been associated with sections of river with riparian areas. Other EPBC Act-listed vertebrate species in the study area include the critically endangered speartooth shark (Glyphis glyphis) and the endangered northern quoll (Dasyurus hallucatus) and the Gouldian finch (Erythrura gouldiae). The freshwater sawfish (Pristis pristis), the dwarf sawfish (Pristis clavata) and the green sawfish (Pristis zijsron) are listed as vulnerable and migratory in the EPBC Act and the dugong as marine and migratory. 9.2 Ecology activity breakdown In order to understand the potential risks to the natural environment associated with water resource development, the ecology activity is using an ecological asset approach and building upon and adapting the methods used in the ecology synthesis and assessment component of the Northern Australia Water Resource Assessment (NAWRA) (Pollino, 2018 #4526 ; Pollino, 2018 #4502 ). This includes undertaking a prioritisation of assets, reviewing and updating asset knowledge bases, conceptual relationships and evidence narratives, including the flow–ecology relationships, and considering their context and application in the Roper catchment. The ecology activity will use a hierarchal modelling approach that utilises a range of assessment methods for a set of prioritised assets that transition from qualitative to more quantitative methods as sufficient relationships between flow and ecological outcomes are sufficiently known and can be suitably supported. The ecology activity modelling will use hydrology scenarios developed by the surface water hydrology activity and compare outcomes as relative differences between scenarios and a baseline. 9.2.1 Prioritisation of assets For the purpose of the ecology activity, assets are classified as species, functional groups or habitats and can be considered as either partially or fully freshwater dependent, or marine dependent upon freshwater flows. To identify priority assets to undertake the ecological analysis, a review and prioritisation of assets will be undertaken for the Roper catchment, building upon the asset descriptions developed by Pollino, 2018 #4502 ). For the purposes of this Assessment, assets are defined as: • being listed as threatened, vulnerable or endangered species or communities • being wetlands, species or communities that are formally recognised in international agreements • providing vital, near-natural, rare or unique habitat for water-dependent flora and fauna • supporting significant biodiversity for water-dependent flora and fauna • providing recreational, commercial or cultural value. From the full range of potential assets occurring in the Roper catchment, the process for selecting priority assets will consider if they are: • representative – to capture a range of flow requirements for biota and ecological processes • distinctive – to enable a broad representation of water requirements • describable – with sufficient peer-reviewed evidence available to describe relationships with flow • significant – considering ecological, conservation, cultural and recreational importance. 9.2.2 Conceptual modelling and evidence base Conceptual models will be used to describe the ecological understanding of the assets, including flow relationships and other influences that may contribute to the sustainability, function or health of the asset. The conceptual models provide a framework to underpin the analyses of the impacts of water resource development by providing a knowledge and evidence base linking key drivers to outcomes. Standardised conceptual models will be adapted or developed that synthesise the best available knowledge of flow–ecology relationships considering aspects such as life history, flow triggers, movement, refuge, productivity, water quality or connectivity requirements as relevant for each ecological asset. The conceptual models will include key potential risks from a range of sources, including water resource development and changes in land use, as well as physical changes (e.g. increases in sedimentation), water quality changes (e.g. increased nutrients) and invasive species (spread of pests and weeds), and articulate how these can result in changes in ecology or to the asset. Assets will be mapped across the Roper catchment to understand their distribution and important habitat associations. By considering their distribution across the catchment, we can identify where they will be exposed to changes in the flow associated with different water resource developments. A range of data sources will be explored to develop maps and spatial relationships of these assets in the Roper catchment. 9.2.3 Analysis of potential ecological impacts The ecology activity will undertake an assessment of the potential impacts for the prioritised assets using a hierarchal modelling approach. This approach will provide a consistent framework to understand ecological impacts resulting from flow regime changes. The modelling approach will incorporate semi-quantitative and quantitative modelling methods, with each method considering the asset’s knowledge base and the ability to support quantitative relationships between flow, ecological responses and outcomes. The ecological analysis will utilise daily hydrology data generated with river system and hydrodynamic models to understand the relative differences between scenarios and a baseline, by considering the types of changes in the flow regime, the asset flow relationships and the distribution of assets within the catchment using the asset mapping. The ecological analysis will include a ‘flow requirements assessment’, a ‘habitat suitability assessment’ and a ‘connectivity assessment’. Each are described briefly below. Flow requirements assessment The flow requirements (hydrometrics – statistical properties of the long-term flow regime) assessment identifies the key components of the hydrograph important for each asset. This assessment calculates the change in these asset-specific hydrometrics occurring between the baseline and the model scenarios. The relative differences between sites and scenarios can be compared to understand what scenarios are likely to impact which ecological assets and where. Habitat suitability assessment The habitat suitability (preference curve) assessment captures how components of flow meet the habitat needs of the selected assets. The preference curves relate an attribute of flow to a condition value of the asset. A set of preference curves will be used for each asset to generate an overall condition score for the baseline and modelled hydrology scenarios. The preference curves consider ecological needs such as movement, breeding or survival requirements, and how changes in key flow attributes impact the asset, considering outcomes such as population size or condition. Connectivity assessment The connectivity assessment uses hydrodynamic modelling to develop a time series of inundation extents for a range of scenarios. For these scenarios, across a sample of flood events, the pattern and extent of inundation will be used to quantify the connectivity of assets (wetlands) to the main river channel via connection across the floodplain or via flood runners. Differences in the connection or duration of connection between the scenarios will be quantified. 9.3 References Barber M and Jackson S (2011) Indigenous water values and water planning in the upper Roper River, Northern Territory. CSIRO: Water for a Healthy Country National Research Flagship, Australia. Bunn SE and Arthington AH (2002) Basic principles and ecological consequences of altered flow regimes for aquatic biodiversity. Environmental Management 30(4), 492–507. Conservation Comission of the Northern Territory Government (1994) A Conservation Strategy for the Northern Territory. Northern Territory Government, Darwin. CSIRO (2009) Water in the Gulf of Carpentaria Drainage Division. A report to the Australian Government from the CSIRO Northern Australia Sustainable Yields Project. CSIRO Water for a Healthy Country Flagship, Australia. Dasgupta, S., Blankenspoor, B., Herzog, T. & Davies, A. Terrestrial biodiversity indicators. doi:https://datacatalog.worldbank.org/dataset/terrestrial-biodiversity-indicators (2019). Department of the Environment. Directory of Important Wetlands in Australia, (2010). Faulks JJ (2001) Roper River catchment – an assessment of the physical and ecological condition of the Roper River and its major tributaries. Technical report no. 36/2001. Department of Lands, Planning and Environment, Katherine, NT. Griffiths AD (1997) Biological survey of Elsey National Park. Technical report no. 63. Parks and Wildlife Commission of the Northern Territory. Junk WJ, Bayley PB and Sparks RE (1989) The flood pulse concept in river-floodplain systems. Canadian Special Publication of Fisheries and Aquatic Sciences 106, 110–127. Kenyon R, Burridge C, Poiner C and Hopkins E (1999) Impact of the McAuthur River project mine transhipment facility on the marine environment. CSIRO Marine Research, Cleveland Queensland. Lynch RJ and Catterall CP (1999) Riparian wildlife and habitats. In: Lovett S and Price P (eds) Riparian land management technical guidelines, volume one: principles of sound management. LWRRDC, Canberra. Northern Territory Government (2010) Gulf water study: Roper River facts. Northern Territory Government, Darwin. Northern Territory Government (2019) Sites of conservation significance: Limmen Bight and associated coastal floodplains Northern Territory. Northern Territory Government, Darwin. Poff LN and Zimmerman JKH (2010) Ecological responses to altered flow regimes: a literature review to inform the science and management of environmental flows. Freshwater Biology 55, 194–205. Poff NL, Allan JD, Bain MB, Karr JR, Prestegaard KL, Richter BD, Sparks RE and Stromberg JC (1997) The natural flow regime: a paradigm for river conservation and restoration. BioScience 47(11), 769–784. Pollino C, Barber E, Buckworth R, Cadiegues M, Deng R, Ebner B, Kenyon R, Liedloff A, Merrin L, Moeseneder C, Morgan D, Nielsen D, O’Sullivan J, Ponce Reyes R, Robson B, Stratford D, Stewart-Koster B and Turschwell M (2018a) Synthesis of knowledge to support the assessment of impacts of water resource development to ecological assets in northern Australia: asset analysis. A technical report to the Australian Government from the CSIRO Northern Australia Water Resource Assessment, part of the National Water Infrastructure Development Fund: Water Resource Assessments, Australia. Pollino C, Barber E, Buckworth R, Cadiegues M, Deng R, Ebner B, Kenyon R, Liedloff A, Merrin L, Moeseneder C, Morgan D, Nielsen D, O’Sullivan J, Ponce Reyes R, Robson B, Stratford D, Stewart-Koster B and Turschwell M (2018b) Synthesis of knowledge to support the assessment of impacts of water resource development to ecological assets in northern Australia: asset descriptions. A technical report to the Australian Government from the CSIRO Northern Australia Water Resource Assessment, part of the National Water Infrastructure Development Fund: Water Resource Assessments, Australia. Part V Case studies, reports, key protocols and standards 10 Case studies 10.1 Rationale By its nature, the Assessment will produce information from a very broad range of disciplines. This is as it should be because the development of northern Australia will require the integration of knowledge from a similarly broad range of disciplines. The purpose of the case studies is to help readers: • understand how to ‘put the Assessment information together’ to answer their own questions about water resource development in the Roper catchment • understand the type and likely scale of opportunity of different types of water resource development in selected geographic parts of the Assessment area • explore some of the nuances associated with ‘greenfield’ developments in the Roper catchment, which are often difficult to capture in discipline-based information. 10.1.1 What the case studies are designed to do and not to do Although the case studies are designed to be realistic representations – that is, they will be ‘located’ in specific parts of the Assessment area, and use specific water and land resources, and realistic intensification options – they are illustrative only. They are not designed to demonstrate, recommend or promote particular development opportunities being proposed by individual development proponents, nor are they CSIRO’s recommendations on how development in the Roper catchment should unfold. 10.2 Proposed case study framings The specific case studies will be developed over time as the Assessment proceeds, and the Assessment team begins to assemble information from a range of sources and disciplines. These sources will include ideas generated by stakeholders within the Assessment area and will be guided by current enterprise types found in the Assessment area. Proposed case studies will then be tested with the Program Steering Committee before being finalised. Although the case studies are yet to be developed, the following framings can be used as a guide: 1. large schemes, privately funded (greater than about $500 million) 2. large schemes, publicly funded (greater than about $500 million) 3. medium-sized schemes, such as might be developed by pastoral corporates or large family businesses (from tens of millions of dollars to about $500 million) 4. small-scale schemes, such as an individual or family business might develop (from about $1 million to about $10 million). Coupled to this framing, various methods of water capture and supply will be considered. Various agricultural systems will be included in the case studies. The case studies will consider the costs and challenges of supplying water using various configurations of capture and distribution, the timing of water supply and demand, assumptions concerning annual water yield (at varying reliabilities), and conveyance and field application losses. Soil and landscape attributes will be considered in terms of their proximity to the water supply, risks such as secondary salinity, and suitability for various crop and aquaculture types. Interactions and links with other industries (e.g. the beef industry), processing facilities, transport logistics, and hard and community infrastructure requirements will be factored in. The case studies will be grounded within the social and cultural context of the Roper catchment, including infrastructure availability and constraints. Economic analyses will consider gross margins, as well as the ability of the enterprise to service capital costs. One way to envisage what these case studies will look like is to consider those used in previous land and water resource studies in the Flinders catchment (Petheram et al., 2013a), the Gilbert catchment (Petheram et al., 2013b) and the Northern Australia Water Resource Assessment (Petheram et al., 2018). 10.3 References Petheram C, Hughes J, Stokes C, Watson I, Irvin S, Musson D, Philip S, Turnadge C, Poulton P, Rogers L, Wilson P, Seo L, Pollino C, Ash A, Webster T, Yeates S, Chilcott C, Bruce C, Stratford D, Taylor A, Davies P and Higgins A (2018) Case studies for the Northern Australia Water Resource Assessment. A report to the Australian Government from the CSIRO Northern Australia Water Resource Assessment, part of the National Water Infrastructure Development Fund: Water Resource Assessments, Australia. Petheram C, Watson I and Stone P (eds) (2013a) Agricultural resource assessment for the Flinders catchment. A report to the Australian Government from the CSIRO Flinders and Gilbert Agricultural Resource Assessment, part of the North Queensland Irrigated Agriculture Strategy. CSIRO Water for a Healthy Country and Sustainable Agriculture flagships, Australia. Petheram C, Watson I and Stone P (eds) (2013b) Agricultural resource assessment for the Gilbert catchment. A report to the Australian Government from the CSIRO Flinders and Gilbert Agricultural Resource Assessment, part of the North Queensland Irrigated Agriculture Strategy. CSIRO Water for a Healthy Country and Sustainable Agriculture flagships, Australia. 11 Reports, products, protocols and standards 11.1 Reports, products and protocols The Assessment management team will provide quality assurance for all data and reports produced from the Roper River Water Resource Assessment. To meet this objective, the team will: • provide templates, standards, processes and workflows for reporting • provide collaborative working spaces (including SharePoint, Google Drive) • review all technical material • ensure that sensitive and important modelling is undertaken within a best modelling practice framework – that is, a three-stage independent review process of i) conceptual model, ii) calibration model, and iii) simulation model • edit and produce catchment and summary reports • develop processes, and provide information sheets and training to Assessment members on data management protocols, the CSIRO metadata catalogue, and the CSIRO data access portal and data audit trails. SharePoint is a website that provides a central storage for the Assessment team to share documents that require version control. The Assessment team will store all versions of the catchment and summary report documents on the CSIRO SharePoint website. All final versions of the technical reports will be stored on the SharePoint CSIRO SharePoint website . A OneDrive site has been established for the Assessment team. This will be the team’s primary collaboration space to share non-sensitive documents, calendars, photos, meeting minutes, guideline documents and videos, stakeholder contact information and other similar material. Table 1-1 details key deliverables for the Roper River Water Resource Assessment. These will be complemented by a minimum of six technical reports, which will provide the technical underpinning for the summary material. Alternative (non-report) products for the delivery of information to key stakeholders will include incorporation of river models into NAWRA river (NAWRA River Model website ) and other datasets into the NAWRA explorer (NAWRA Explorer website ). The CSIRO data access portal will be used as the final repository for key datasets such as the land suitability grids. 11.2 Standards The Assessment management team will define editorial standards to guide authors in reporting the findings of the Assessment. These standards will include map and figure conventions, and will be available in a document titled Reporting standards. These standards are based on: • the Australian Government Style manual for authors, editors and printers • CSIRO brand identity guidelines • standards used in the Flinders and Gilbert Agricultural Resource Assessment and the Northern Australia Sustainable Yields (NASY) projects • the Australian Oxford dictionary. Since many specialist terms are not found in these resources, additional conventions specific to the Assessment will be developed in consultation with the Assessment team. Reporting standards will be a ‘living document’ that changes as the Assessment progresses, to document decisions on language and formatting. Conventions specified in early drafts, however, will not be changed unless necessary; the aim is to add conventions, not to backtrack on earlier decisions. Reporting standards will be published as a report at the end of the Assessment. As Australia’s national science agency and innovation catalyst, CSIRO is solving the greatest challenges through innovative science and technology. CSIRO. Unlocking a better future for everyone. Contact us 1300 363 400 +61 3 9545 2176 csiroenquiries@csiro.au csiro.au For further information Environment Dr Chris Chilcott +61 8 8944 8422 chris.chilcott@csiro.au Environment Dr Cuan Petheram +61 467 816 558 cuan.petheram@csiro.au Agriculture and Food Dr Ian Watson +61 7 4753 8606 Ian.watson@csiro.au