Water resource assessment for 
the Southern Gulf catchments 

 
Australia’s National 
Science Agency 
A report from the CSIRO Southern Gulf Water Resource 
Assessment for the National Water Grid 

Editors: Ian Watson, Caroline Bruce, Seonaid Philip, Cuan Petheram and Chris Chilcott 

 

 



ISBN 978-1-4863-2081-3 (print) 

ISBN 978-1-4863-2082-0 (online) 

Citation 

Watson I, Bruce C, Philip S, Petheram C and Chilcott C (eds) (2024) Water resource assessment for the Southern Gulf catchments. A report from the 
CSIRO Southern Gulf Water Resource Assessment for the National Water Grid. CSIRO, Australia. 

Chapters should be cited in the format of the following example: Philip S, Watson I, Petheram C and Bruce C (2024) Chapter 1: Preamble. In: Watson 
I, Bruce C, Philip S, Petheram C, and Chilcott C (eds) (2024) Water resource assessment for the Southern Gulf catchments. A report from the CSIRO 
Southern Gulf Water Resource Assessment for the National Water Grid. CSIRO, Australia. 

Copyright 

© Commonwealth Scientific and Industrial Research Organisation 2024. 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, 
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CSIRO is committed to providing web accessible content wherever possible. If you are having difficulties with accessing this document, please 
contact Email CSIRO Enquiries
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CSIRO Southern Gulf Water Resource Assessment acknowledgements 

This report was funded through the National Water Grid’s Science Program, which sits within the Australian Government’s Department of Climate 
Change, Energy, the Environment and Water. 

Aspects of the Assessment have been undertaken in conjunction with the Northern Territory (NT) and Queensland governments. 

The Assessment was guided by two committees: 

i. The Governance Committee: CRC for Northern Australia/James Cook University; CSIRO; National Water Grid (Department of Climate 
Change, Energy, the Environment and Water); Northern Land Council; NT Department of Environment, Parks and Water Security; NT 
Department of Industry, Tourism and Trade; Office of Northern Australia; Queensland Department of Agriculture and Fisheries; 
Queensland Department of Regional Development, Manufacturing and Water 
ii. The Southern Gulf catchments Steering Committee: Amateur Fishermen’s Association of the NT; Austral Fisheries; Burketown Shire; 
Carpentaria Land Council Aboriginal Corporation; Health and Wellbeing Queensland; National Water Grid (Department of Climate 
Change, Energy, the Environment and Water); Northern Prawn Fisheries; Queensland Department of Agriculture and Fisheries; NT 
Department of Environment, Parks and Water Security; NT Department of Industry, Tourism and Trade; Office of Northern Australia; 
Queensland Department of Regional Development, Manufacturing and Water; Southern Gulf NRM 


Responsibility for the Assessment’s content lies with CSIRO. The Assessment’s committees did not have an opportunity to review the Assessment 
results or outputs prior to their release. 

This report was reviewed by Mr Mike Grundy (Independent consultant). Individual chapters were reviewed by Dr Peter Wilson, CSIRO (Chapter 2); 
Dr Andrew Hoskins, CSIRO (Chapter 3); Dr Brendan Malone, CSIRO (Chapter 4); Dr James Bennett, CSIRO (Chapter 5); Dr Nikki Dumbrell, CSIRO 
(Chapter 6); Mr Darran King, CSIRO (Chapter 7). The material in this report draws largely from the companion technical reports, which were 
themselves internally and externally reviewed. 

For further acknowledgements, see page xxviii. 

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 

Saltwater Arm, a tributary of the Albert River. This view typifies the tidal rivers and estuaries along the southern coast of the Gulf of Carpentaria. 
Source: Shutterstock


Director’s foreword 

Sustainable development and regional economic prosperity are priorities for the Australian, 
Queensland and Northern Territory (NT) governments. However, more comprehensive 
information on land and water resources across northern Australia is required to complement 
local information held by Indigenous Peoples and other landholders. 

Knowledge of the scale, nature, location and distribution of likely environmental, social, cultural 
and economic opportunities and the risks of any proposed developments is critical to sustainable 
development. Especially where resource use is contested, this knowledge informs the consultation 
and planning that underpin the resource security required to unlock investment, while at the same 
time protecting the environment and cultural values. 

In 2021, the Australian Government commissioned CSIRO to complete the Southern Gulf Water 
Resource Assessment. In response, CSIRO accessed expertise and collaborations from across 
Australia to generate data and provide insight to support consideration of the use of land and 
water resources in the Southern Gulf catchments. The Assessment focuses mainly on the potential 
for agricultural development, and the opportunities and constraints that development could 
experience. It also considers climate change impacts and a range of future development pathways 
without being prescriptive of what they might be. The detailed information provided on land and 
water resources, their potential uses and the consequences of those uses are carefully designed to 
be relevant to a wide range of regional-scale planning considerations by Indigenous Peoples, 
landholders, citizens, investors, local government, and the Australian, Queensland and NT 
governments. By fostering shared understanding of the opportunities and the risks among this 
wide array of stakeholders and decision makers, better informed conversations about future 
options will be possible. 

Importantly, the Assessment does not recommend one development over another, nor assume 
any particular development pathway, nor even assume that water resource development will 
occur. 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. 

 

Chris Chilcott 

C:\Users\bru119\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Word\C_Chilcott_high.jpg
Project Director 

 














Key findings for the Southern Gulf catchments 
The Southern Gulf catchments have an area of 108,200 km2 across the Northern Territory (NT) and 
Queensland. They comprise the catchments of Settlement Creek (17,600 km2), Nicholson River 
(52,200 km2), Leichhardt River (33,400 km2) and, Morning Inlet (3,700 km2) and the Wellesley 
island groups (1,200 km2). The rivers of these catchments flow into the lower Gulf of Carpentaria, 
an important part of northern Australia’s marine environment with high ecological, cultural and 
economic values. Within the study area, 12% of the land is Aboriginal freehold tenure of which 
33% is national park, including the UNESCO World Heritage-listed Australian Fossil Mammal Sites 
(Riversleigh, Queensland). The dominant land use by area is extensive grazing of beef cattle on 
native rangelands, constituting 77% of the study area. Mining occupies less than 0.05% of the land 
area and irrigated agriculture, occupies about 0.01% (~1,400 ha). 
The population of the catchments in 2021 was approximately 22,500 people, of whom about 27% 
were Indigenous Australians. In comparison, Indigenous Australians make up 25% of the 
population of the NT, 4% of the population of Queensland and 3% of Australia as a whole. There is 
one significant urban area, Mount Isa (population 18,000) and Doomadgee (population 1,387) is 
the only other settlement with a population greater than 1,000. Distinct demographic and socio-
economic differences exist within the Southern Gulf catchments based on the differences between 
Mount Isa and the remainder of the study area. The population density outside Mount Isa is one 
of the lowest in Australia, and some communities in the study area are ranked as being among the 
most disadvantaged in Australia. 
Indigenous Peoples have continuously occupied and managed the Southern Gulf catchments for 
tens of thousands of years. They retain significant and growing rights and interests in land and 
water resources, including crucial roles in water and development planning and as co-investors in 
future development. Indigenous Peoples remain closely tied to their territory associations. The key 
language groups are Garawa, Gangalidda, Waanyi, Kukatj, Lardil, Yangkaal, Kaiadilt, Wakabunga, 
Nguburinji, Kalkadoon, Mitakoodi, Mayi-Kutuna, Mayi‑Thakurti, Mayi‑Yapi and Mayi-Yali. A 
number of related groups and subgroups occur within these regional ownership descriptors. 
The creeks and rivers of the Southern Gulf catchments contribute about 6% of the mean annual 
discharge into the Gulf of Carpentaria, supporting many important ecological assets, some of 
national significance, and existing industries such as the Northern Prawn Fishery. 
This fishery had a prawn catch across whole of northern Australia valued at $85 million in 
2019–20. While the Leichhardt River is deeply incised over much of its length, high-flow 
distributary channels have formed where the Nicholson and Gregory rivers flow across the 
extensive Armraynald Plain.
The Nicholson and Leichhardt rivers are the two largest rivers in the Southern Gulf catchments and 
have median annual discharges of 1,873 and 1,211 GL, respectively. The Settlement Creek 
catchment encompasses numerous relatively short rivers, including Running, Settlement, Lagoon, 
Eight Mile, Cliffdale and Moonlight creeks. The median annual discharge from the creeks within 
the Settlement Creek catchment is 1,304 GL. The Gregory River, which flows into the Nicholson 
ii | Water resource assessment for the Southern Gulf catchments 












River approximately 85 km from the coast, is the largest perennial river in semi‑arid Queensland. 
The Gregory River and its major tributary, Lawn Hill Creek, receive groundwater discharge 
throughout the dry season from the Cambrian Limestone Aquifer (CLA), which is comprised mostly 
of the Camooweal Dolostone and Thorntonia Limestone in the south of the study area. 
The concentration of mining and industrial activity around Mount Isa has resulted in sufficiently 
high water demand from high-value industries for the construction of five large, purpose-built 
reservoirs of at least 10 GL capacity in the Leichhardt catchment, including the Leichhardt Dam 
(Lake Moondarra) and Julius Dam (Lake Julius). Consequently, as a proportion of its median annual 
streamflow, the water in the Leichhardt River is more heavily regulated than most other rivers in 
northern Australia west of the Great Dividing Range. As a result of existing entitlements 
(105.7 GL/year) and licence conditions in the Leichhardt catchment, only limited quantities of 
water could be reliably available for irrigated agriculture from Julius Dam without affecting the 
reliability of water supply to existing water entitlement holders. The study area has numerous 
small dams (<10 GL) providing water to mines as well as farm-scale dams, several for irrigation, but 
the only other instream water structure of note is a low weir (<1 GL capacity) on the Nicholson 
River downstream of Doomadgee, which is used to supply water for the town. 
With irrigation, the Southern Gulf catchments have a climate that is suitable for a wide range of 
annual and perennial horticulture, and broadacre crops and forages. However, the opportunities 
and risks of irrigation development adjacent to each of the major rivers are starkly different. 
Adjacent to the east bank of the Gregory River downstream and slightly upstream of the township 
of Gregory, the grey cracking clay soils of the treeless Armraynald Plain are highly favourable for 
large-scale irrigation developments (based on instream dams) or small-scale irrigation 
developments (based on water harvesting). The large contiguous areas of soil suitable for 
broadacre irrigation and ringtanks (1.03 million ha) gently slope away from the Gregory River, 
enabling water to be efficiently distributed using gravity and natural distributary channels running 
away from the river. The most cost-effective potential site for a dam in the study area is located 
approximately 70 km upstream of the township of Gregory, but that potential dam’s reservoir 
would be located within a part of the Gregory River that is a nationally significant wetland, the 
Thorntonia Aggregation. Being one of the few perennial rivers in the Southern Gulf and 
neighbouring Flinders catchment region, the Gregory River is particularly highly valued by local 
residents. 
On the Nicholson River downstream of Doomadgee are contiguous areas of red sandy and loamy 
soils (totalling 23,000 ha) suitable for irrigated vegetables. However, in the absence of a dam 
upstream, on-farm storage of water for irrigated annual horticulture would be challenging due to 
the difficulty of constructing ringtanks on these sandy soils. These soils are unlikely to be suitable 
for perennial horticulture due to the risk of flooding. 
The Leichhardt catchment has opportunities for irrigated horticulture on the friable soils 
(103,000 ha) on the narrow levees of the Leichhardt River downstream of Kajabbi. Adjacent to 
these soils, and up to 1 km from the river, are friable clay soils suitable for broadacre irrigation. 
While these heavier soils are suitable for constructing ringtanks, conveying water pumped from 
the Leichhardt River across the sandy levee soils to ringtanks may be costly and inefficient in some 
locations. The proximity of the eastern side of the mid-reaches of the Leichhardt River to the Burke 
Developmental Road and Mount Isa would be an advantage to new irrigation developments 


compared with more remote parts of northern Australia. For example, the more remote Nicholson 
and Settlement Creek catchments are often inaccessible for long periods due to flooding during 
the wet season. 

It is physically possible that water harvesting could extract 150 GL of water in 75% of years, spread 
across the Nicholson and Leichhardt catchments, without affecting the reliability of supply of 
existing water entitlement holders. This extraction would reduce the median and mean annual 
discharge to the Gulf of Carpentaria from these catchments by 5% and 3%, respectively. It would 
be sufficient water to irrigate about 12,000 ha of mixed broadacre crops. 

A hypothetical total of 10,000 ha of irrigated mixed broadacre (85%) and horticulture (15%) 
agriculture in the Southern Gulf catchments, would result in total annual increased economic 
activity (direct and indirect) of potentially as much as $190 million and support up to 360 full-time-
equivalent jobs. 

In reality, the nature and scale of future surface water development would depend heavily upon 
community and government values, acceptance of potential impacts to water-dependent 
ecosystems, and the likely beneficiaries. Economic data from the NT and north-western 
Queensland indicate that, like other industries such as mining, grazing and fishing, benefits arising 
from agriculture developments elsewhere in the NT and Queensland have been heavily skewed to 
non-Indigenous households relative to Indigenous households. 

The most promising groundwater resources in the Southern Gulf catchments are the regional-
scale CLA and Gilbert River Aquifer (GRA). The CLA coincides with large, contiguous areas of 
cracking clay soils suitable for irrigated broadacre cropping (308,000 ha) along the south-western 
margin of the study area. However, groundwater discharge from the CLA provides the dry-season 
flow in Lawn Hill Creek and the Gregory and O’Shannassy rivers and some of their tributaries. The 
major rivers of the Southern Gulf catchments are also characterised by relatively extensive alluvial 
aquifers, up to 5 km either side of the river. These systems are poorly characterised but likely to be 
highly heterogeneous and connected to the rivers, meaning the alluvial aquifers could be 
recharged by and discharge into ‘connected’ rivers at different times of the year. In addition to the 
3.5 GL of existing groundwater entitlements in the study area, it is physically possible that 
groundwater systems across the Southern Gulf catchments could supply up to approximately 30 
GL of water per year for irrigated agriculture, sufficient to irrigate about 4,000 ha of mixed 
broadacre cropping. Up to 10 GL of additional groundwater per year could potentially be extracted 
for other uses from areas of hard rock (i.e. poor soil) and poor water quality. The actual quantity of 
water extracted, however, would depend on community and government acceptance of impacts 
to groundwater-dependent ecosystems (GDEs) and existing groundwater users. 

Irrigated agriculture and aquaculture in the Southern Gulf catchments is only likely to be 
financially viable where there is an alignment of good prices for high‑value crops and market 
advantages. This makes achieving scale challenging. Other factors include availability of suitable 
markets for the products, investment in fundamental infrastructure such as all-weather roads and 
bridges and land tenure arrangements. New agricultural developments in the study area, if they 
were to eventuate, are likely to start irrigating broadacre crops on heavier clay soils before 
progressing to higher‑value and higher-input enterprises, such as horticulture on sandy and loamy 
soils, as farmers build confidence in their skills and expertise in this largely greenfield region. 
Landholders could potentially transition from broadacre cropping to annual horticulture on the 


heavy clay soils and nearby sandy levees adjacent to the Leichhardt River. Along the lower coastal 
reaches, about 194,000 ha of land is suitable for prawn and barramundi aquaculture, using 
earthen ponds. For all of the area estimates noted above, the land is considered suitable but with 
minor to considerable limitations and would require careful soil management. 

Growing irrigated forages or hay to feed young cattle to improve market access or to enable sale 
at younger ages is unlikely to be financially viable. Irrigation increases beef production but 
requires high capital outlay, and gross margins would be reasonably similar to, or less than, 
baseline cattle operations. Consistent rainfed cropping in the catchment is likely to be 
opportunistic (only possible in suitable years) and depend upon farmers’ appetite for risk and 
future local demand. How land cultivated for rainfed agriculture is managed in the years when 
rainfall is insufficient for rainfed cropping will be crucial for sustainable farming operations and the 
industry’s social licence to operate. 

Changes to groundwater baseflow and streamflow under projected drier future climates are likely 
to be considerably greater than changes that would result from plausible groundwater and surface 
water developments. Of the global climate models examined, 44% projected a drier future climate 
over the Southern Gulf catchments and 40% projected ‘little change’. Adopting a conservatively 
dry global climate model projection of a 13% reduction in long‑term mean annual rainfall and a 9% 
increase in potential evaporation, the modelled reduction in median annual discharge to the Gulf 
of Carpentaria from the Nicholson and Leichhardt catchments was 30%. 

The Southern Gulf catchments, although not pristine, have many unique characteristics and 
valuable ecological assets, which support existing industries such as grazing, tourism and 
commercial fishing. Whether based on groundwater or offstream storage, irrigated agricultural 
development has a wide range of potential benefits and risks that differentially intersect diverse 
stakeholder views on ecology, economy and culture. The detailed reports upon which this 
summary is based provide information that can be used to help consider the trade-offs from 
potential developments. 



Leichhardt River flowing through the Isa Highlands 

Photo: CSIRO – Nathan Dyer 



Overview of the Southern Gulf catchments 

The Southern Gulf catchments comprise four river basins defined by the Australian Water 
Resource Council, referred to here as catchments, that discharge into the Gulf of Carpentaria: 
Settlement Creek, Nicholson, Leichhardt and Morning Inlet. The study area also encompasses the 
Wellesley islands groups. 

The Southern Gulf catchments have a highly variable climate 

Northern Australia’s tropical climate is notable for the extremely high variability of rainfall 
between seasons and especially between years. This has major implications for evaluating and 
managing risks to development, infrastructure and industry. 

The climate of the Southern Gulf catchments is hot and semi-arid to dry subhumid. Generally, 
these catchments are water-limited environments, so efficient and effective methods for 
capturing, storing and using water are critical. 


•The mean and median annual rainfall – averaged across the Southern Gulf catchments – are 
602 mm and 554 mm, respectively. A strong rainfall gradient runs from Mornington Island in the 
north (1,150 mm annual median) to the south of Mount Isa (400 mm annual median).
•Averaged across the catchments, 6% of the rainfall occurs in the dry season (May to October). 
Median annual dry‑season rainfall ranges from 15 mm in the south-east to 60 mm along the 
western boundary.
•Annual rainfall totals in the Southern Gulf catchments are highly variable. Annual totals are 
approximately 1.3 times more variable than in comparable parts of the world.


The seasonality of rainfall presents opportunities and challenges for both wet- and dry-season 
cropping. 

•Information about water availability (i.e. soil water and water in storages) helps minimise risk 
when it is known ahead of important agricultural decisions – before planting time for most 
dry-season planted crops. Such information allows farmers to manage risk by choosing crops 
that optimise use of the available water or by deciding to forego cropping for a season.


Rainfall is difficult to store. 

•Mean annual potential evaporation is higher than rainfall, averaging about 1,850 mm over mostof the study area, with the highest values near the mouth of the Leichhardt River and MorningInlet.
•Large farm-scale ringtanks lose about 30% to 50% of their water to evaporation and seepagebetween April and October. Deeper farm-scale gully dams lose about 20% to 40% of their waterover the same period. Using stored water early in the season is the most effective way to reducethese losses.


The more promising agricultural land in the Southern Gulf catchments is in the middle to lower 
reaches of the rivers, which are the parts of the study area most susceptible to destructive 
cyclonic winds. 


•Of the 53 consecutive cyclone seasons prior to 2021–22, the Southern Gulf catchments had notropical cyclones in 60% of those seasons, one cyclone in 36% of seasons and two cyclones in 4%
of seasons.


More than twice as many global climate models project a drier future climate than a wetter 
future climate for the Southern Gulf catchments, thus it is prudent to plan for water scarcity. 

•For the Southern Gulf catchments, 44% of climate models project a drier future, 16% project awetter future and 40% project a future within ±5% of the historical mean, indicating ‘littlechange’. Other studies indicate that tropical cyclones will be fewer but more intense in thefuture, although uncertainties remain.
•Palaeoclimate records indicate past climates have been both wetter and drier over the pastseveral thousand years.
•Climate and hydrology data that support short- to medium-term water resource planning shouldcapture the full range of likely or plausible conditions and variability at different timescales, andparticularly for periods when water is scarce. These are the periods that most affect industryand the environment. When industries ‘compete’ with the environment for water when it ismost scarce, it can have profound long-term consequences to both if the scarcity is poorlyunderstood and not planned for.
•Future changes in temperature, vapour pressure deficit, solar radiation, wind speed and carbondioxide concentrations will separately act to increase or decrease crop water demand and cropyield under irrigation in northern Australia. For example, during the cooler months of the dryseason, cotton in the more southerly parts of the Southern Gulf catchments (e.g. BarklyTableland) may be limited by minimum temperatures at key stages of cotton boll development.
Higher temperatures may increase the irrigation water requirement, depending upon whetherother climate variables such as wind speed increase or decrease in the future. However, forsome crops, higher crop water demand, and hence smaller planted area, could be offset byhigher yields and lower risk of crop failure.
•Changes under future climates to the amount of irrigation water required and crop yield arelikely to be modest compared to improvements arising from new crop varieties and technologyover the next 40 years. Historically, these types of improvements have been difficult to predict,
but they are potentially large.


The Southern Gulf catchments are comprised of many different types of rivers and creeks 

The rivers and creeks of the Southern Gulf catchments constitute about 6% of the mean annual 
flow into the Gulf of Carpentaria, an important part of northern Australia’s marine environment 
with high ecological and economic values. 

•The mean and median annual discharges from the Southern Gulf catchments into the Gulf ofCarpentaria are 6,759 and 4,961 GL, respectively.
•The Nicholson and Leichhardt rivers are the two largest rivers in the Southern Gulf catchments.
The Nicholson River has the 13th largest median annual discharge (1,873 GL) of all rivers thatflow into the Gulf of Carpentaria, and the Leichhardt River has the 16th largest (1,211 GL).



•The Settlement Creek catchment encompasses numerous relatively short creeks and its medianannual discharge to the Gulf of Carpentaria is 1,304 GL. The median annual discharges from theMorning Inlet catchments and the Wellesley Island groups are 195 and 173 GL, respectively.
•Annual variability in streamflow in the Southern Gulf catchments is comparable with other riversin northern Australia with similar mean annual runoff, but the annual variability in runoff is twoto three times greater than rivers in the rest of the world in similar climates.


Broad-scale flooding occurs along the lower reaches of the rivers of the Southern Gulf 
catchments, particularly adjacent to the distributary channels from the Nicholson and Gregory 
rivers to the Albert River. 

•Between 1980 and 2023 (43 years), 51 streamflow events broke the banks of the Gregory Riverat Riversleigh Road crossing. All events occurred between November and April (inclusive), andabout 84% of events occurred between January and March (inclusive).


Under a potential dry future climate (13% reduction in rainfall), median annual discharges from 
the Nicholson and Leichhardt rivers are projected to decrease by approximately 30%. 

The Leichhardt catchment is one of the most regulated catchments in northern Australia, west 
of the Great Dividing Range, based on extractions as a proportion of its median annual flow. 

•Current licensed surface water extractions in the Leichhardt catchment are about 105.7 GL/year(~7% of median annual discharge). However, actual mean annual water use is estimated to beless than half this amount.
•Discounting tailings dams, the Leichhardt catchment contains five dams listed in the AustraliaNational Committee on Large Dams register: Julius Dam (107.5 GL capacity), Leichhardt RiverDam / Lake Moondarra (103 GL capacity), Greenstone Creek / Waggaboonya Lake (Greenstone)
(13.6 GL capacity), East Leichhardt Dam / Lake Mary Kathleen (12.1 GL capacity) and Rifle CreekDam (9.5 GL capacity). With the exception of East Leichhardt Dam, which is now only used forrecreation, the dams supply water for mining, industry and town uses.
•Water quality is variable across the Southern Gulf catchments. Studies in the late 2000s foundthe water quality of the upper Leichhardt River had been influenced by urban and miningactivity and exceeded a number of heavy metal water quality guideline trigger values, howeverthe drinking water source for Mount Isa (Lake Moondarra) was found to meet drinking waterguidelines.


The Gregory River, which flows into the Nicholson River approximately 85 km from the coast, is 
the largest perennial river in semi‑arid Queensland. 

•Lawn Hill Creek and the Gregory and O’Shannassy rivers receive groundwater dischargethroughout the dry season from the CLA, which is composed mostly of the CamoowealDolostone and Thorntonia Limestone.
•On average, approximately 87% of the streamflow in the Southern Gulf catchments occursbetween January and March. In the perennial Gregory River, however, approximately 78% ofstreamflow occurs over the same time period.



The Southern Gulf catchments contain a significant diversity of species and habitats, 
including freshwater, terrestrial and marine habitats of great cultural, conservation and 
commercial importance 

The Southern Gulf catchments are largely intact, but they are not pristine. 

• A range of economic enterprises, infrastructure and human-induced impacts occur in the 
Southern Gulf catchments, and the nature and extent to which these have modified the habitats 
and affected species of the Southern Gulf catchments vary. 
• The near-coastal and estuary habitats of the Southern Gulf catchments support fishing 
industries, including a commercial barramundi fishery, prawns and mud crabs (mainly Scylla 
serrata). 
• In the Leichhardt catchment, Lake Julius and Lake Moondarra are listed in the Directory of 
Important Wetlands in Australia (DIWA). While the water in these two storages predominantly 
supplies urban, mining and industrial demand around Mount Isa and Cloncurry, the permanent 
water provides important dry-season refuge for waterbirds and supports a variety of freshwater 
fish species. 
• In the Southern Gulf catchments, feral horses, wild pigs and cane toads are among the 
introduced animals. 
• Weed species of interest in and around the Southern Gulf catchments include prickly acacia, 
buffel grass, salvinia rubber vine and water hyacinth. 


Floods have economic significance because they underpin the health of the recreational and 
commercial fisheries in the Gulf of Carpentaria, which include a barramundi fishery and the 
Northern Prawn Fishery, which had a catch of prawns worth $85 million in 2019–20. 

• Wet-season flooding inundates significant parts of the lower reaches of the rivers in the 
catchments, connecting wetlands to river channels, inundating floodplains, and allowing the 
exchange of fauna, flora and nutrients, which drives an ecological productivity boom. 
• The 13 DIWA-listed wetlands in the Southern Gulf catchments include a variety of wetland 
types, ranging from estuarine wetlands with salt flats and saltmarshes to artificial lakes and 
spring-fed creeks and rivers. 
• Protected areas located in the Southern Gulf catchments include the UNESCO World Heritage-
listed Australian Fossil Mammal Sites (Riversleigh, Queensland), which is in Boodjamulla 
National Park (Queensland), and Finucane Island National Park (Queensland). There are also 
three Indigenous Protected Areas: Ganalanga‑Mindibirrina, NT; Nijinda Durlga, Queensland; and 
Thuwathu/Bujimulla, Queensland. 
• The marine, near-shore and estuarine environments of the Southern Gulf catchments have 
extensive intertidal flats and estuarine communities, including mangroves, salt flats, coral reefs 
and seagrass habitats. These habitats are highly productive, have high cultural value and include 
many areas of national significance. 
• Seagrass beds in the near-coastal Gulf of Carpentaria have high diversity and grow in vigorous 
stands. They provide important food and habitat for dugongs (Dugong dugon), green sea turtles 
(Chelonia mydas) and prawns (Penaeus spp.). 



• The dominant vegetation types in the catchments are open eucalypt woodlands, Melaleuca 
forests and woodlands, and, on the cracking clay plains, tussock grasslands characterised by the 
Mitchell grasses (Astrebla spp.). 
• The marine and near-shore marine areas of the catchments contain significant habitat for sea 
turtles, shorebirds and seabirds. 
• Protected species include freshwater or largetooth sawfish (Pristis pristis; Vulnerable, EPBC Act) 
and the Gulf snapping turtle (Elseya lavarackorum). 
• The Southern Gulf catchments provide important stopover habitat for migratory shorebird 
species listed under the EPBC Act, including the eastern curlew (Numenius madagascariensis; 
Critically Endangered) and the Australian painted snipe (Rostratula australis; Endangered). 


Indigenous values, rights and development goals 

Indigenous Peoples are a significant and increasing population of the Southern Gulf catchments. 

• Traditional Owners have recognised native title and cultural heritage rights, have Aboriginal 
freehold land ownership and control, or are the custodians of, significant natural and cultural 
resources, including land, water, coastline and sea. 
• Water-dependent fishing and hunting are key health, customary and economic roles for 
Indigenous Peoples in the Southern Gulf catchments. The rivers and underground water support 
food security and good nutrition, and are crucial to geographical and cultural relationships. 
• The history of pre-colonial and colonial patterns of land and natural resource use and 
preservation in the Southern Gulf catchments is important to understanding present 
circumstances. This history has shaped residential patterns, including across the Queensland–NT 
border, and it also informs responses by the Indigenous Peoples to future development 
possibilities. 
• The Indigenous population of the Southern Gulf catchments outside the Mount Isa urban centre 
is 60% of the total population. 


From an Indigenous perspective, ancestral powers are still present in the landscape, including 
underground water, and they intimately connect Peoples, Country and culture. 

• Those powers must be considered in any action that takes place on Country. 
• Patterns of ownership and language affiliation follow features of the landscape and waterways 
and are reflected in the place names and songs of significant Dreamings and totemic figures. 
• Water is central to the cultural landscape. Riverine and aquatic areas are known to be strongly 
correlated with cultural heritage sites. 
• Some current cultural heritage considerations restrict Indigenous capacity to respond to 
development proposals because some knowledge is culturally sensitive and cannot be shared 
with those who do not have the cultural right and authority to know. 


Catchment-wide deliberative processes will be vital to ensuring that Indigenous water rights and 
interests are actively engaged and included in future water-dependent development and 
planning. 


• Indigenous Peoples, especially those in the downstream parts of the catchments, see 
environmental impact assessments as crucial tools to assist them to make decisions about 
water-dependent development. 
• Indigenous Peoples have business and water development objectives designed to create 
opportunities for existing residential populations, including the supply of safe and secure 
community water to residents, and to aid the return of Peoples living elsewhere. 
• Indigenous Peoples want to be owners, partners, investors and stakeholders in any future 
development. This reflects their status as the longest-term residents with deep inter-
generational ties to the catchment. Indigenous custodians in the catchments are engaged in 
diverse collaboration and partnership models with the private, non-government, government 
and research sectors. 


Opportunities for agriculture and aquaculture 

There is about 1,400 ha of irrigated agriculture and 4,000 ha of rainfed agriculture in the 
Southern Gulf catchments. 

Although an abundance of soil is suitable for irrigated agriculture in the Southern Gulf 
catchments, the area that can be irrigated is limited by water. 

• Up to about 5.1 million ha of soils in the Southern Gulf catchments are classified as moderately 
suitable with considerable limitations (Class 3) or better (Class 1 or Class 2) for irrigated 
agriculture, depending on the crop and irrigation method chosen. 
• Class 3 soils have considerable limitations that lower production potential or require more 
careful management than more suitable soils, such as Class 2 soils. 
• About 4.7 million ha of soils in the Southern Gulf catchments are rated as Class 3 or better for 
irrigated pulses (i.e. food legumes) using spray irrigation in the dry season. Most of this area is 
rated as Class 2. In comparison, about 1.7 million ha of soils are rated Class 3 or better using 
furrow irrigation in the dry season for the same crops. 
• About 4.7 million ha of soils in the Southern Gulf catchments are rated as Class 3 or better for 
cotton or grains crops using spray irrigation in the dry season. Under furrow irrigation in the dry 
season, there are about 1.8 million ha of soil suitable for cotton or grain crops, all of which are 
rated as Class 3. 


Bushfoods are an emerging niche industry across northern Australia. Kakadu plum, though not 
recorded as occurring in the Southern Gulf catchments, is one of the best known and has one of 
the most well-developed supply chains. However, most bushfoods continue to be 
wild‑harvested with very little grown commercially. Limited information on commercial 
bushfood operations is publicly available. 

The soils in different parts of the study area are starkly different. 

• The largest arable areas in the Southern Gulf catchments are the self-mulching cracking clay soils 
of the Armraynald Plain (1.03 million ha) and Barkly Tableland (308,000 ha). The cracking clay 
soils are likely to present severe trafficability constraints throughout much of the wet season. 
Irrigation of the Armraynald Plain and Barkly Tableland would be best suited to use of surface 
water and groundwater respectively. 



•Downstream of Doomadgee are large contiguous areas of red sandy and loamy soils suitable forirrigated vegetables (23,000 ha) along the Nicholson River. However, in the absence of a damupstream, on-farm storage of water for broad-scale irrigation would be challenging due to thedifficulty of constructing ringtanks on these sandy soils. These soils are unlikely to be suitable forperennial horticulture due to the risk of flooding. It may be possible to slightly raise and enhancethe existing weir on the Nicholson River near Doomadgee to provide some additional water toirrigate small-scale market gardens either on these sandy and loamy soils or on similar soilscloser to Doomadgee.
•The Leichhardt catchment has opportunities for irrigated horticulture on the friable soils(103,000 ha) on the narrow levees of the Leichhardt River downstream of Kajabbi. Adjacent tothese soils, and up to 1 km from the river, are friable clay soils suitable for broadacre irrigation.
While these heavier soils are suitable for constructing ringtanks, conveying water pumped fromthe Leichhardt River across the sandy levee soils to ringtanks may be costly and inefficient insome locations.


Irrigation enables higher yields and more flexible and reliable production than rainfed 
crops 

•Many annual crops can be grown at most times of the year with irrigation in the Southern Gulfcatchments. Irrigation provides increased yields and flexibility in sowing date.
•Sowing dates must be selected to balance the need for the best growing environment(optimising solar radiation and temperature) with water availability, pest avoidance,
trafficability, crop sequences, supply chain requirements, infrastructure requirements, marketdemand, seasonal commodity prices and, in the case of genetically modified cotton, plantingwindows specified within the cotton industry.
•Irrigated crops likely to be commercially viable with a dry-season planting (late March to August)
include annual horticulture, cotton and mungbean. Irrigated crops likely to be commerciallyviable with a wet-season planting (December to early March) include cotton, forages andpeanuts.
•Seasonal irrigation water applied to crops can vary enormously with crop type (e.g. due tovariations in duration of growth, rooting depth), season of growth, soil type and rainfallreceived. For example, cotton planted in the wet season and dry season requires about 5 ML/haand 6 ML/ha, respectively, of irrigation water in at least 50% of years. A high-yielding perennialforage such as Rhodes grass requires up to about 20 ML/ha each year, averaged across a fullproduction cycle.
•Rainfed cropping is theoretically possible but most likely to be opportunistic in the Southern Gulfcatchments based on rainfall received and stored soil water.How cultivated land is managed inthe years when rainfall is insufficient for rainfed cropping will be crucial for sustainable farmingoperations and the industry’s social licence to operate.


Excess rainfall can also constrain crop production on some soils. 

•High rainfall and possible inundation mean that wet-season cropping on the alluvial clay soils ofthe Armraynald Plain carries considerable risk due to potential difficulties with access topaddocks, trafficability, waterlogging of immature crops and deteriorating water quality where



agricultural runoff is poorly managed.• Accumulation of soil salinity due to irrigation over time 
in these soils is currently unknown and would need to be monitored, especially in the 
imperfectly drained soils on the northern part of the Armraynald Plain. 


Establishing irrigated cropping in a new region (i.e. greenfield development) is challenging. It has 
high input costs, high capital requirements and requires an experienced skills set. 

• For broadacre crops, gross margins of the order of $4,000 per hectare per year are required to 
provide a sufficient return on investment where on-farm development capital costs are about 
$20,000/ha. Crops likely to achieve such a return include cotton and to a lesser extent Rhodes 
grass hay, noting that the gross margins of hay are highly sensitive to local demand, price and 
the transport costs. 
• Horticultural gross margins would have to be higher (of the order of $7,000 to $11,000 per 
hectare per year) to provide an adequate return on the higher capital costs of developing this 
more intensive type of farming (relative to broadacre). Profitability of horticulture is extremely 
sensitive to prices received, so the locational advantage of supplying out-of-season (winter) 
produce to southern markets is critical to viability. Annual horticulture row crops would be the 
most likely to achieve these returns in the Southern Gulf catchments, but would be marginal. 


Growing more than one crop per year may enhance the viability of greenfield irrigation 
development. 

• There are proven benefits to sequentially cropping more than one crop per year in the same 
field in northern Australia, particularly where additional net revenue can be generated from the 
same initial investment in farm development. 
• Numerous options for crop sequences could be considered, but these would need to be tested 
and adapted to the particular opportunities and constraints of the Southern Gulf catchments’ 
soils and climates. While somewhat opportunistic, the most likely sequential farming systems 
could be those combining short-duration crops such as annual horticulture (e.g. melons), 
mungbean, chickpea and grass forages. Following a rainfed wet-season crop with an irrigated 
dry-season crop might also be possible. 
• Trafficability constraints on the alluvial clay soils will limit the options for sequential cropping 
systems. The well‑drained loamy soils on elevated plains near Doomadgee and the friable soils 
adjacent to the Leichhardt River pose fewer constraints for scheduling sowing times and the 
farm operations required for sequencing two crops in the same field each year. Even so, 
sequential cropping systems would be very tight operationally. 
• Tight scheduling requirements mean that even viable crop sequences may be opportunistic. The 
challenges in developing locally appropriate sequential cropping systems, and the management 
packages and skills to support them, should not be under-estimated. 


Irrigated cropping has the potential to produce off-site environmental impacts, although these 
can be mitigated by good management and new technology. 

• The pesticide and fertiliser application rates required to sustain crop growth vary widely among 
crop types. Selecting crops and production systems that minimise the requirement for pesticides 
and fertilisers can simultaneously reduce costs and negative environmental impacts. 



•Refining application rates of fertiliser to better match crop requirements, using controlled-
release fertilisers and improving irrigation management, are effective ways to minimise nutrientadditions to waterways and, hence, the risk of harmful microalgae blooms.
•Adherence to well-established best management practices can significantly reduce erosionwhere intense rainfall and slope would otherwise promote risk. This would also decrease the riskof herbicides, pesticides and excess nitrogen entering the natural environment.
•More than 99% of the cotton grown in Australia is genetically modified. The geneticmodifications have allowed the cotton industry to substantially reduce insecticide (by greaterthan 85%) and herbicide application to much lower levels than previously used. In addition toreducing the likelihood and severity of off-site impacts, genetically modified crops offer healthbenefits to farm workers who handle fewer chemicals. This technology has considerablerelevance to northern Australia.


Irrigated forages can increase the number of cattle sold and the income of cattle enterprises. 
However, the increased income is usually offset by the high initial capital costs and ongoing 
costs of irrigating a forage crop. 

•The dominant beef production system in the Southern Gulf catchments is a cow–calf breedingenterprise, with several markets possible. There is limited fattening of cattle within the studyarea, and many cattle are moved to different parts of Queensland before their final destination.
•While native pastures are generally well adapted to harsh environments, they imposeconstraints on beef production through their low productivity and digestibility and theirdeclining quality through the dry season. Growing irrigated forages and hay would allow higher-
quality feed to be fed to specific classes of livestock to achieve higher production and/ordifferent markets. These species could include perennial grasses, forage crops and legumes.
•Grazing of irrigated forages by young cattle, or feeding them hay, decreases the time they taketo reach sale weight and, in particular, increases their daily weight gain through the dry season.
•While ostensibly simple, there are many unknowns regarding the best way to implement asystem whereby irrigated forages and hay are grown on-farm to augment an existing cattleproduction system.
•Growing forages or hay to feed young cattle for the export market was not financially viable inthe modelled scenarios tested when capital costs were considered.While beef production andtotal income increased, gross margins were reasonably similar to, or less than, baseline cattleoperations.


Pond-based black tiger prawns or barramundi (in saltwater) or red claw crayfish (in fresh 
water) offer potentially high returns 

Along the coastal reaches of the Southern Gulf catchments, approximately 194,000 ha of land is 
suitable for prawn and barramundi aquaculture, using earthen ponds. 

•A large (i.e. 100 ha) pond-based marine culture aquaculture farm typically uses less than 
4 GL/year of freshwater.



•Prawn and barramundi aquaculture elsewhere have proven land-based production practices andwell‑established markets for harvested products. These are not fully established for otheraquaculture species being trialled in northern Australia.
•Prawns could potentially be farmed in either extensive (low-density, low-input) or intensive(higher-density, higher-input) pond-based systems. Land-based farming of barramundi wouldlikely be intensive.
•The most suitable areas of land for pond-based marine aquaculture systems are restricted to theareas of the catchment under tidal influence and the river margins where cracking clay andseasonally or permanently wet soils dominate.
•Annual operating costs for intensive aquaculture are so high that they can exceed the initial costof developing the enterprise. Operational efficiency is therefore the most importantconsideration for new enterprises, particularly the production efficiency in converting feed tosaleable product.


Surface water storage potential 

Indigenous customary, residential and economic sites are usually concentrated along major 
watercourses and drainage lines. Consequently, potential instream dams are more likely to have 
an impact on areas of high cultural significance than are most other infrastructure developments 
of comparable size. 

•Complex changes in habitat resulting from inundation could create new habitat to benefit somespecies, while other species could experience a negative impact through loss of habitat.


Many of the upland regions of the Southern Gulf catchments are topographically and 
geologically favourable for large instream dams. However, the semi-arid climate and small 
catchment areas would result in most potential dam sites being relatively low yielding. 


•The most cost-effective potential dam sites in the Southern Gulf catchments are on the Gregory 
River and Gunpowder Creek. In the 1960s and 1970s, the Queensland Water Supply 
Commission investigated potential dam sites on both drainage lines.
•Potential dam sites on the Gregory River at natural constrictions upstream of the township of 
Gregory are the highest yielding and most cost-effective due to the large streamflow and 
proximity to large contiguous areas of black and grey cracking clay soils of the Armraynald Plain. 
The topography, sloping away from the Gregory River, enables cheap gravity-based methods of 
distributing water.
•A hypothetical dam on the Gregory River upstream of Gregory with a reservoir full supply level 
such that it does not extend into the Boodjamulla National Park could yield 133 GL in 85% of 
years and cost $683 million (−20% to +50%) to construct, assuming favourable geological 
conditions. This would be sufficient water to support approximately 10,000 ha of dry-season 
cropping under surface irrigation, with the reticulation infrastructure costing approximately 
$38 million, or $3,800 per hectare of irrigated land.
•A previous study found that residents of Mount Isa place high value on particular rivers. The 
Gregory River, being one of the few perennial rivers in north‑west Queensland, has a high value 
to Indigenous and non‑Indigenous residents.



•A hypothetical dam on Gunpowder Creek could potentially yield 119 GL in 85% of years and cost$773 million. If used for agriculture, the nearest suitable soils are approximately 35 kmdownstream near the junction of Gunpowder Creek and the Leichhardt River. This would besufficient to irrigate approximately 11,000 ha of dry-season broadacre and horticultural cropsunder spray irrigation. However, the grade of the land and the sandy texture of the surface soilsmean that water would need to be piped from the river, greatly increasing the cost ofreticulation infrastructure (estimated to be about $320 million or $29,000 per hectare ofirrigated land).
•The higher cost of the irrigation schemes associated with a potential dam at Gunpowder Creekcompared to the potential site on the Gregory River mean that high‑value annual horticulturewould need to be grown on the friable soils downstream of the former site to offset the highercosts, assuming there was a market for the produce.
•Although there are some potential dam sites on the Nicholson River, this part of the study areais particularly remote, greatly increasing capital and ongoing costs.


On-farm water storages may have more prospects of being commercially viable than large 
instream dams in the Southern Gulf catchments. 

•Suitably sited large farm-scale gully dams are a relatively cost-effective method of supplyingwater. Although most sites are located in the uplands, where the soil is rocky and shallow andless suitable for their construction and irrigated agriculture, some locations – such as thenorth‑western part of Settlement Creek, Mornington Island, the lower Leichhardt River andupper parts of Morning Inlet – have a coincidence of topography and soils that is favourable forgully dams and irrigated agriculture.


The alluvial clay soils on the Armraynald Plain offer different opportunities and risks to the 
loamy soils near Doomadgee. 

•Approximately 21% of the Southern Gulf catchments has soils that are likely to be suitable forthe construction of ringtanks. The most promising areas are the cracking clay soils of theArmraynald Plain east of the Gregory River and downstream of Gregory, where the natural slopeaway from the river enables the cost-effective conveyance of water using gravity.
•Except for in the lower reaches of the Nicholson River, the soils of the Nicholson catchment aregenerally too sandy for ringtanks. The Leichhardt River downstream of Kajabbi has soils suitablefor ringtanks; however, sandy levees adjacent to the river can be up to 1 km wide, increasingconveyance costs and/or losses. Further downstream, although the soils are suitable forringtanks adjacent to the Leichhardt River, to the west the land slopes towards the river, whichwould result in additional pumping costs.
•With water harvesting it is physically possible to extract 150 GL of water in 75% of years,
assuming an even split between the Nicholson and Leichhardt catchments, without havingimpacts on the reliability of water supply to existing licensed users. This quantity of water issufficient to irrigate about 12,000 ha of broadacre crops during the dry season by pumping ordiverting water and storing it in offstream storages such as ringtanks. This would result inreductions in the mean and median annual discharges to the Gulf of Carpentaria from theNicholson and Leichhardt catchments of about 3% and 5%, respectively.



Energy infrastructure constraints are a key consideration for energy‑intensive 
enterprises in the Southern Gulf catchments 

•Mount Isa and immediate surrounds are provided power by the North West Power System.
•As a grid isolated from the rest of the Queensland electricity grid, the availability of generationon the North West Power System is largely matched to the existing demand of the major miningcustomers. Dispatch protocols may place limits on availability of power to new large retailcustomers, such as a large irrigation development.
•Capacity on the existing Ergon 220kV transmission line that runs from Mount Isa to CenturyMine is limited, and new developments would need to negotiate with both Ergon and majorcustomers on the line to obtain the required energy and capacity.
•New energy-intensive enterprises would require development of dedicated electricaldistribution infrastructure such as new substations and distribution lines.
•CopperString 2032 will connect the North West Power System to the National Electricity Market,
alleviating any constraints in generation. However, constraints in the transmission anddistribution system would remain.


Development of a large in-river storage solely for hydro-electric power purposes would 
not be commercially feasible in the Southern Gulf catchments. 

Other existing and potential industries that depend on water 

Mining 

The Southern Gulf catchments fall within the North West Minerals Province, which is considered 
to be one of the world’s most significant areas for producing base and precious metals. Mining is 
by far the largest industry in the study area and has an annual value more than 100 times that of 
grazing. 

•Mining provides about 28% of all jobs in the Southern Gulf catchments.
•Mount Isa is in a period of transition, with major lead, copper and zinc mines in the regionrecently closing or scheduled to cease operations imminently. However, technological advances(e.g. batteries, super magnets, electronics, medical imaging) have resulted in increased demandfor rare earth elements. These are referred to as critical minerals and strategic materials, andthe NT and Queensland governments have programs to attract investment in exploration andinfrastructure.
•Occurrences of critical minerals and strategic materials have been recorded in the Southern Gulfcatchments, and mineral and petroleum exploration leases cover 67% of the study area. Futuredemand for minerals is highly speculative.


Across Australia, mining uses about one-tenth of the water used by irrigated agriculture, though 
water for mining is assigned a higher reliability than agriculture, which makes water use 
comparisons difficult. 


•The amount of water used for mining is highly variable depending upon a wide range of factors,
including mining methods, ore types, ore grades and processing treatments. With the exceptionof coal mines, which are not found in the Southern Gulf catchments, and large gold mines,
individual mines typically use less than 0.5 GL/year.
•Many uses of water by mining enterprises (e.g. dust suppression, cooling, slurry and processwater) do not require the water to be of potable quality.
•Because water is typically a very small fraction of the total input cost of a mine, and miningproduces high‑value products, mining enterprises have the capacity to develop their own watersupplies. In the Southern Gulf catchments, the historical concentration of mining, industrial andurban activity around Mount Isa resulted in sufficiently high water demand for the constructionof large, purpose-built reservoirs.
•Recent water use from existing reservoirs in the Mount Isa region is estimated to be modestrelative to total supplemented entitlements (<35%), indicating that the existing dams havescope to supply water for a modest expansion of mining, depending upon the location ofpotential mines.
•There is limited scope for existing or new dams in the Southern Gulf catchments to be used forboth mining and irrigated agriculture because high-value minerals are located in areas with hardrock, which tend to be distant from large contiguous areas of soil suitable for irrigatedagriculture, such as alluvial plains.


Petroleum extraction and de-watering of mine pits produce water that needs to be treated and 
appropriately disposed. 

Tourism 

The Southern Gulf catchments have a highly seasonal and relatively low volume of visitation, 
largely due to their climate, remoteness, sparse population and limited tourism development. 

•Annual visitation to the study area is estimated to result in approximately $150 millionexpenditure. Most visitors go to Mount Isa, and a large proportion (~60%) of visitors travelling toMount Isa are on business (which cannot be separated in the visitation statistics).
•Although tourism in northern Australia consumes very small quantities of water relative to otherindustries, the state of northern Australia’s tourism economy is closely tied to the state andperceived attractiveness of its ecosystems, including its rivers and water‑dependent ecosystems.
•Self-drive is the predominant tourism market, representing 87% of visitors to outbackQueensland. Many self-drive visitors are motivated by experiencing an ancient, vast and ‘empty’landscape with opportunities for exploration and solitude.
•With a large proportion of the Southern Gulf catchments in a relatively ‘undisturbed’ state,
there is potential for growth in nature-based tourism, particularly as Mount Isa’s airportprovides a commercial gateway to the region and critical infrastructure that many other parts ofnorthern Australia lack. However, the remoteness of the region and lack of supportinginfrastructure beyond Mount Isa considerably constrain tourism’s potential, as does the highseasonality of visitation, which limits enterprise profitability and year-round employmentopportunities.



•Much of the appeal of the Southern Gulf catchments to self-drive tourists is likely to be theabsence of human and commercial infrastructure, so development that alters the region’scurrent characteristics could be either appealing or alienating to current tourist markets.


While water resource development for agriculture has the potential to negatively affect tourism 
opportunities in the Southern Gulf catchments, some developments and associated supporting 
infrastructure (e.g. roads, accommodation) may, conversely, present opportunities to foster 
tourism growth. 

•Lake Argyle in the east Kimberley region (WA) developed as an irrigation dam to supply the OrdRiver Irrigation Area. It is now advertised as one of WA’s most spectacular attractions, offering awide range of tourism activities. Studies have identified that Lake Argyle is perceived by visitorsin a similar fashion to some ‘natural’ local attractions such as billabongs. The cultivated land ofthe Ord River Irrigation Area, however, is reportedly perceived by visitors differently, as being‘domesticated’.
•Due to the presence of Lake Moondarra and Lake Julius, the recreational value of additionaldams near Mount Isa is unlikely to make a discernible impact on the local economy, thoughdams in more remote regions of the Southern Gulf catchments could encourage self-drivetourists to stay in those regions longer.
•Tourism has the potential to enable economic development within Indigenous communitiesbecause Indigenous tourism enterprises, which are usually micro businesses, often havecompetitive advantages.
•While tourism offers economic and employment opportunities, it can also cause impacts such asclearing of vegetation and environmental damage due to foot, bike or vehicle traffic. This canreduce amenity for local residents and increase risks such as the potential for the spread ofweeds, pests, or root rot fungus.


The Southern Gulf catchments have productive groundwater systems 

Groundwater systems in the Southern Gulf catchments are poorly studied. Nonetheless, it is 
estimated that they could potentially supply up to approximately 40 GL of water per year in 
addition to the 3.5 GL/year of existing licensed entitlements, depending on community and 
government acceptance of impacts to groundwater-dependent ecosystems (GDEs) and existing 
groundwater users. 

•Not all of this water could be used for irrigated agriculture, due to poor water quality, distanceto suitable soil, and/or low bore yields.• The most promising groundwater resource in theSouthern Gulf catchments is the regional-scale Cambrian Limestone Aquifer (CLA), which ismostly comprised of the Camooweal Dolostone and Thorntonia Limestone. With appropriatelysited groundwater borefields, it is physically possible that multiple small- to intermediate‑scale(1 to 3 GL/year) groundwater-based enterprises could extract approximately 10 to 20 GL/year ofwater from the CLA, depending on community and government acceptance of impacts to GDEsand existing groundwater users.
•The mean annual recharge across the CLA within the Southern Gulf catchments is estimated tobe approximately 160 GL. The conservative mean annual recharge is estimated to be between40 and 80 GL.



•The CLA outcrops along the south-western part of the Southern Gulf catchments. Groundwaterdischarge from the aquifer occurs from ecologically and culturally important springs and pointsof lateral outflow where the streams are incised into the CLA along Lawn Hill Creek and theGregory and O’Shannassy rivers.
•Groundwater from the CLA varies from very fresh (<500 mg/L total dissolved solids (TDS)) tobrackish (<3,000 mg/L TDS), which is towards the upper limit of salinity for most crops.


The regional-scale Gilbert River Aquifer (GRA) within the geological Carpentaria Basin underlies 
the central and northern parts of the study area. 

•The GRA does not outcrop within the Southern Gulf catchments, so there is no direct rechargeto this aquifer within the study area. Recharge predominantly occurs as lateral inflow ofgroundwater from the east of the Leichhardt catchment boundary.
•With appropriately sited groundwater borefields, it is possible that multiple small- tointermediate-scale (1 to 3 GL/year) developments could extract up to approximately 5 GL/yearfrom the GRA.
•The GRA is shallowest (<250 m below ground level (mBGL)) at its south-western basin margin inthe mid‑reaches of the study area. It hosts some fresh water (<1,000 mg/L TDS) in places alongits south-western margin between Settlement Creek and the Leichhardt River. The GRAincreases in depth in a north-east direction towards the coast (>400 mBGL), and the waterbecomes increasingly brackish (>2,000 mg/L TDS), presenting economic challenges forgroundwater infrastructure.
•The GRA becomes artesian approximately 20 to 50 km from its southern basin margin, andartesian conditions extend into the Gulf of Carpentaria.
•Potential opportunities for future groundwater resource development are likely to be limitednear existing licensed groundwater users, such as the communities of Burketown and Gununa,
where the GRA is at depths of greater than 500 mBGL. Neither licence is currently in use, due tothe naturally poor water quality of the aquifer.
•It is unknown whether the GRA contributes groundwater to springs and seeps within the studyarea, though it is unlikely, given the depth of the aquifer.


Collectively, other groundwater systems in the Southern Gulf catchments may yield 
approximately 15 GL/year. 


•The Cenozoic alluvial aquifers in the mid- to lower reaches of the Nicholson, Gregory and 
Leichhardt rivers, and Settlement Creek and its tributaries, host local-scale groundwater 
systems. However, data are very sparse, and these water resources remain poorly understood. 
Imagery of the study area appears to indicate that alluvial material is more laterally extensive 
than found elsewhere in northern Australia.
•Alluvial aquifers have potential for multiple small-scale (<0.5 GL/year) localised developments or 
as a conjunctive water resource where surface water is available. Opportunities are likely to be 
limited where the saturated thickness of the aquifer is thin (<10 m), as well as in areas within 
1 km of the prescribed watercourses of the Nicholson, Gregory and Leichhardt rivers. Impacts 
on local GDEs would need to be evaluated, because streamflow and persistent waterholes in 
some rivers are potentially supported by groundwater discharge from the alluvium.



•The sparse groundwater data available for the alluvial aquifers suggest that the groundwaterquality in these systems is good (<600 mg/L TDS) in places.
•Fractured and weathered rock aquifers are hosted in a variety of Proterozoic rocks across thesouthern, central and northern parts of the study area. These aquifers are highly variable incomposition and water quality, and typically groundwater bores yield little water (<2 L/s).
Where these aquifers occasionally exhibit higher yields, due to extensive fracturing and jointing,
they are often storage limited.


There is potential to undertake managed aquifer recharge in aquifers of the Cenozoic alluvium 
and in the CLA. 

•The most promising aquifers for infiltration-based managed aquifer recharge in the Southern 
Gulf catchments are aquifers within the Cenozoic alluvium, which is associated with many of 
the major rivers in the study area. However, there are few bore logs and limited groundwater‑level information available for the Cenozoic alluvium, and it is likely the opportunity for MAR 
may vary between locations. If an alluvial aquifer is found to be suitable for MAR, it will be more 
cost-effective to extract groundwater in the first instance.


Changes in volumes and timing of river flows have ecological impacts 


•Although irrigated agriculture occupies only a small percentage of the landscape, relatively small 
areas of irrigation can use large quantities of water, and the resulting changes in the flow regime 
can have profound effects on flow-dependent flora and fauna and their habitats.
•Changes in river flow may extend considerable distances downstream and onto the floodplain, 
including into the marine environment, and their impacts can be exacerbated by other changes, 
including changes to connectivity, water quality and invasive species. The magnitude and spatial 
extent of ecological impacts arising from water resource development are highly dependent on 
the type of development, location, timing, extraction volume and mitigation measures 
implemented.
•Ecological impacts, inferred here by calculating change in ecological flow dependency for a range 
of fresh water–dependent ecological assets for the Nicholson and Leichhardt catchments, 
increases non-linearly with increasing scale of surface water development (i.e. large instream 
dams and water harvesting). A change in ecological flow dependency does not necessarily 
correlate to change in ecological condition. Change in ecological condition varies between assets 
depending on the importance of river flow to each asset’s condition and other drivers (e.g. 
rainfall, local runoff, groundwater).
•At equivalent levels of water resource development (i.e. in terms of volume of water extracted), 
and without mitigation measures the mean impact on surface‑flow‑dependent ecology of an 
instream dam on a major tributary of the Leichhardt River was found to be less than water 
harvesting averaged across the Leichhardt catchment. The mean impact of an instream dam on 
the Gregory River averaged across the Gregory –Nicholson catchment was found to be larger 
than water harvesting.
•Mud crabs, mullet, threadfin and prawn species are among the ecological assets most affected 
by flow changes for water harvesting. However, different types of development affected assets 
differently.



•Water harvesting developments extracting a total of 50 to 300 GL/year of water from the 
Nicholson and Leichhardt catchments without mitigation strategies resulted in minor and 
negligible changes to ecology flow dependencies of freshwater assets when averaged across 
each catchment respectively. Local impacts below points of extraction, however, were generally 
moderate for freshwater assets at the higher extraction volumes and generally minor for 
near-shore marine assets at higher extraction volumes.


Mitigation strategies that protect low flows and first flows of a wet season are successful in 
reducing impacts on ecological assets. These can be particularly effective if implemented for 
water harvesting developments. 

•At equivalent volumes of water extraction, imposing an end-of-system (EOS) annual flowrequirement, where water harvesting can only commence after a specified volume of water hasflowed past the EOS and into the Gulf of Carpentaria, is an effective mitigation measure forwater harvesting. However, the efficacy of this mitigation measure is reduced with a pump-startthreshold of 600 ML/day, as is required to ensure there are no impacts on existing consumptivewater users.
•The additional impact caused by water harvesting developments extracting 150 GL/year andwith a pump-start threshold of 600 ML/day is less across most ecological assets than the impactof existing levels of development and use compared with pre‑European development.
•A dry future climate has the potential to have a larger mean impact on ecological flowdependencies across the Nicholson and Leichhardt catchments than the largest physicallyplausible water resource development scenarios. However, the perturbations to flow arisingfrom a combined drier future climate and water resource development result in greater impactson ecology flow dependency than either factor on their own.


For instream dams, location matters, and there is potential for high risks of local impacts. 
Improved outcomes are associated with maintaining attributes of the natural flow regime. 

•Potential dams may result in an extreme change in the ecological flow dependency of someassets immediately downstream of the dam. However, impacts reduce downstream with theaccumulation of additional tributary flows, so when averaged over the entire catchment ormeasured at the EOS, the change in ecological flow dependency is minor.
•Providing translucent flows (flows allowed to ‘pass through’ the dam for ecological purposes)
improves flow regimes for ecology, particularly for perennial rivers like the Gregory River. Itdoes, however, reduce the yield from the dam’s reservoir.


But it is not just flow, other impacts and considerations are also important. 

•At catchment scales, the direct impacts of irrigated agriculture on the terrestrial environmentare relatively small. However, indirect impacts such as weeds, pests and landscapefragmentation may be considerable, particularly in riparian zones.
•Loss of connectivity associated with new instream structures and changes in low flows may limitmovement patterns of many species within the catchment.



Inefficient farm practices, poorly managed irrigation outflows and uncontrolled runoff from 
irrigation areas close to drainage lines may have a larger impact on ecological condition than 
likely changes in river flow patterns and volume in the Southern Gulf catchments. 

•Nitrogen, phosphorus and potassium are the three primary nutrients used in agriculturalfertilisers. Irrigation outflows and tailwater runoff from irrigation events can be high in thesenutrients as well as in pesticides, herbicides and total dissolved solids.
•If best practice is not followed, the concentrations of these contaminants can be elevated inreceiving surface water and groundwater bodies. However, the extent to which irrigatedagriculture affects the quality of receiving waters is highly variable. It depends on a wide rangeof factors, including crop type, farm management and mitigation measures, type and scale ofdevelopment, water application method, proximity to drainage lines and environmental factorssuch as climate, soil type, topography, hydrogeochemistry and susceptibility of irrigated land toflooding.
•Studies in parts of Queensland with a seasonal hydrology have found that first-flow eventsfollowing irrigation or rainfall play a critical role in determining water quality. Studies haveshown that pesticide concentrations in furrow irrigation runoff are highest following initialirrigation events and decrease in subsequent events.
•When pesticide application rates are managed well and irrigation schedules are aligned withcrop growth stages, the concentration of pesticides in receiving waters is typically low, studies inthe Ord River Irrigation Area have found.
•Vegetated areas can intercept agricultural runoff, reducing pesticide concentrations in surfacewaters approximately three times more than areas of bare soil. This highlights the importance ofmaintaining a wide riparian buffer zone.
•Water quality issues will be most significant closest to the source of the contaminant, because ofdilution and naturally occurring processes by which aquatic systems can partially processcontaminants and regulate water quality. Such processes include denitrification of nitrogen andmicrobial degradation and ultraviolet photolysis of pesticides. There are no equivalent naturalprocesses for reducing phosphorus.


Commercial viability and other considerations 

The total annual economic value of irrigated agriculture in the Southern Gulf catchments has the 
potential to increase substantially, from less than $1 million to over $190 million. 

•The estimated total annual gross value of agricultural production in the Southern Gulfcatchments in 2020–21 was $243.6 million. Livestock commodities accounted for most of this,
and cropping accounted for only $0.9 million.
•Agriculture is a relatively small employer in the Southern Gulf Catchments; it is not listed in thetop five industries of employment.





Large dams could be marginally viable if public investors accepted a 3% discount rate or partial 
contributions to water infrastructure costs, similar to established irrigation schemes in other 
parts of Australia. 

•On-farm water storages provide better prospects and, where sufficiently cheap waterdevelopment opportunities can be found, could likely support viable broadacre farms andhorticulture with low development costs.
•Proponents of large infrastructure projects have a systematic tendency to substantially underestimate development costs and risks and to over estimate the scale and rate at which benefitswill be achieved. This Assessment provides information on realistic unit costs and demandtrajectories to allow potential irrigation developments to be benchmarked and assessed on alike-for-like basis.
•The viability of irrigated developments would be determined by: (i) markets and supply chainsthat can provide a sufficient price, scale and reliability of demand, (ii) farmers’ skills in managingthe operational and financial complexity of adapting crop mixes and production systems suitedto the environments of the Southern Gulf catchments, (iii) the nature of water resources interms of the volume and reliability of supply relative to optimal planting windows, (iv) thenature of the soil resources and their proximity to supply chains, and (v) the costs needed todevelop those resources and grow crops compared with alternative locations.


It is prudent to stage developments to manage financial risk and to allow small‑scale trialling on 
new farms. 

•Farm productivity is subject to a range of risks, and setbacks that occur early have the greatesteffect on a development’s viability. A period of initial underperformance must be anticipated forestablishing greenfield farming in a new location, and this must be planned for.
•There is a strong incentive to start any new irrigation development with well-established andunderstood crops, farming systems and technologies, and to incorporate lessons fromagricultural development elsewhere in northern Australia. Local experience and experience fromthe neighbouring Flinders catchment, complemented by learnings from long-establishedirrigation schemes such as the Ord River Irrigation Area and the Burdekin Haughton WaterSupply Scheme, would provide some guidance.
•New agricultural developments in the study area are likely to start irrigating broadacre cropsand pastures on heavier clay soils before progressing to higher-value and more costlyenterprises such as horticulture on sandy and loamy soils.
•Staging allows ‘learning by doing’ at a small scale, where risks can be contained while testinginitial assumptions of costs and benefits and while farming systems adapt to unforeseenchallenges in local conditions.





Irrigated agriculture has a greater potential than rainfed production to generate economic and 
community activity. 

•Studies in the southern Murray–Darling Basin have shown that irrigation generates a level ofeconomic and community activity that is three to five times higher than would be generated byrainfed production.
•Irrigated developments can unlock the economies of scale for supply chains and support servicesthat allow rainfed farming to establish more easily around the irrigated core.
•A large proportion of increased economic activity during the construction phase of potentialirrigation developments in the Southern Gulf catchments would be expected to leak outside thestudy area. Assuming $250 million in capital costs, which could potentially enable 10,000 ha ofirrigated agriculture (~20 new farm-scale developments with on-farm water sources) the totalregional economic activity within the Southern Gulf catchments associated with the constructionphase would be approximately $200 million (assuming 50% leakage out of the study area).
Additional benefits would flow to other regions, including Townsville, Brisbane and potentiallysome areas outside Queensland and the NT.
•The total annual increased economic activity (direct and indirect) from 10,000 ha of irrigatedmixed broadacre (85%) and horticulture (15%) agriculture in the Southern Gulf catchments couldpotentially amount to $190 million, supporting up to 360 full‑time‑equivalent jobs.
••Based on economic data for North West Queensland, the additional income that flowed toIndigenous households from beef cattle developments was about 5% of that which flowed tonon-Indigenous households. For aquaculture, forestry and fishing together the figure was about2.5% and for mining about 6%. The additional income that flowed to Indigenous householdsfrom other agricultural developments (excluding beef) was about 1.5% of that which flowed tonon-Indigenous households. This indicates that, if agricultural developments in the SouthernGulf catchments are to equally benefit Indigenous and non‑Indigenous households, concertedaction will need to be taken by all stakeholders, including government, industry groups andproponents.


Sustainable irrigated development requires resolution of diverse stakeholder values and 
interests. 

•Establishing and maintaining a social licence to operate is a precondition for substantialirrigation development.
•The geographic, institutional, social and economic diversity of stakeholders increases theresources required to develop a social licence and reduces the size of the ‘sweet spot’ in which asocial licence can be established.
•Key interests and values that stakeholders seek to address include the purpose and beneficiariesof development, the environmental conditions and environmental services that developmentmay alter, and the degree to which stakeholders are engaged.





The Southern Gulf Water Resource Assessment Team 

Project Director 

Chris Chilcott 

Project Leaders 

Cuan Petheram, Ian Watson 

Project Support 

Caroline Bruce, Seonaid Philip 

Communications 

Emily Brown, Chanel Koeleman, Jo Ashley, Nathan Dyer 

Activities 

Agriculture and socio-
economics 

Tony Webster, Caroline Bruce, Kaylene Camuti1, Matt Curnock, 
Jenny Hayward, Simon Irvin, Shokhrukh Jalilov, Diane Jarvis1, Adam Liedloff, 
Stephen McFallan, Yvette Oliver, Di Prestwidge2, Tiemen Rhebergen, 
Robert Speed3, Chris Stokes, Thomas Vanderbyl3, John Virtue4 

Climate 

David McJannet, Lynn Seo 

Ecology 

Danial Stratford, Rik Buckworth, Pascal Castellazzi, Bayley Costin, 
Roy Aijun Deng, Ruan Gannon, Steve Gao, Sophie Gilbey, Rob Kenyon, 
Shelly Lachish, Simon Linke, Heather McGinness, Linda Merrin, 
Katie Motson5, Rocio Ponce Reyes, Jodie Pritchard, Nathan Waltham5 

Groundwater hydrology 

Andrew R. Taylor, Karen Barry, Russell Crosbie, Margaux Dupuy, 
Geoff Hodgson, Anthony Knapton6, Stacey Priestley, Matthias Raiber 

Indigenous water 
values, rights, interests 
and development goals 

Pethie Lyons, Marcus Barber, Peta Braedon, Petina Pert 

Land suitability 

Ian Watson, Jenet Austin, Bart Edmeades7, Linda Gregory, Ben Harms10, 
Jason Hill7, Jeremy Manders10, Gordon McLachlan, Seonaid Philip, 
Ross Searle, Uta Stockmann, Evan Thomas10, Mark Thomas, Francis Wait7, 
Peter Zund 

Surface water hydrology 

Justin Hughes, Matt Gibbs, Fazlul Karim, Julien Lerat, Steve Marvanek, 
Cherry Mateo, Catherine Ticehurst, Biao Wang 

Surface water storage 

Cuan Petheram, Giulio Altamura8, Fred Baynes9, Jamie Campbell11, 
Lachlan Cherry11, Kev Devlin4, Nick Hombsch8, Peter Hyde8, Lee Rogers, 
Ang Yang 



Note: Assessment team as at September, 2024. All contributors are affiliated with CSIRO unless indicated otherwise. Activity Leaders are 
underlined. 

1James Cook University; 2DBP Consulting; 3Badu Advisory Pty Ltd; 4Independent contractor; 5 Centre for Tropical Water and Aquatic Ecosystem 
Research. James Cook University; 6CloudGMS; 7NT Department of Environment, Parks and Water Security; 8Rider Levett Bucknall; 9Baynes Geologic; 
10QG Department of Environment, Science and Innovation; 11Entura 


Acknowledgements 

A large number of people provided a great deal of help, support and encouragement to the 
Southern Gulf Water Resource Assessment (the Assessment) team over the past three years. Their 
contribution was generous and enthusiastic and we could not have completed the work without 
them. 

Each of the accompanying technical reports (see Appendix A) contains its own set of 
acknowledgements. Here we acknowledge those people who went ‘above and beyond’ and/or 
who contributed across the Assessment activities. The people and organisations listed below are in 
no particular order. 

The Assessment team received tremendous support from people in the NT Government, 
Queensland Government and associated agencies. They are too numerous to all be mentioned 
here but they not only provided access to files and reports, spatial and other data, information on 
legislation and regulations, groundwater bores and answered innumerable questions but they also 
provided the team with their professional expertise and encouragement. For the NT – Sally 
Heaton, Lauren Cooper, Brad Sauer, Nathaneal Mills, Brett Herbert, Rob Williams and Nerida 
Horner. For Queensland – Greg Mason, Michael Reid, Geoffrey Cahill, Graham Herbert, Ceri 
Pearce, Enrico Perotti, Michelle Smith, Wayne Vogler, Hayden Ferguson and Neale Searle. 

The Assessment acknowledges the staff of the Carpentaria Land Council Aboriginal Corporation 
who guided consultations and provided valuable assistance to plan and execute the on-ground 
meetings with the board members of the Prescribed Body Corporate entities it represents and 
services. It also acknowledges advice provided by staff of other Prescribed Body Corporate entities 
in the upper sections of the Southern Gulf catchments that influenced the focus of the 
Assessment.” 

A number of people in private industry, universities, local government and other organisations 
also helped us. They include Ernie Camp, Mark Thyer, Rob Worlein, Belinda Worlein, William 
Weaver and Craig Cahill. Land managers and landholders at several properties provided 
hospitality, support and information. They include Lorraine, Wernadinga, Cliffdale and Floraville. 

Our documentation, and its consistency across multiple reports, were much improved by a set of 
copy-editors and Word-wranglers who provided great service, fast turnaround times and patient 
application (often multiple times) of the Assessment’s style and convention standards. They 
include Joely Taylor, Margie Beilharz, Jeanette Birtles and Sally Woollett. Greg Rinder provided 
graphics assistance. 

Colleagues in CSIRO, both past and present, provided freely of their time and expertise to help 
with the Assessment. This was often at short notice and of sufficient scale that managing their 
commitment to other projects became challenging. The list is long, but we’d particularly like to 
thank (in no particular order) Tony Zhen, Ali Wood, Nikki Dumbrell, Daniel Grainger, Veronica 
Hannan, Mahdi Montazeri, Ash Shokri, Zaved Khan, Kellie Muffatti, Carmel Pollino, Sonja Serbov, 
Jai Vaze, Francis Chiew, Heather Stewart, Dilini Wijeweera, Jordan Marano, Juliet Morris, Tenneal 
Maskell, Rachel Harm, Jodie Hayward, Heather Stewart, June Chin, Christian Lawrence, Gillian 


Foley, Anne Freer, Sharon Hall, Sonja Heyenga, Amy Edwards, Sally Tetreault Campbell, Larissa 
Sherman, Phil Davies, Anna Rorke and Amy Nicholson. 

This project was funded through the National Water Grid’s Science Program, which sits within the 
Department of Climate Change, Energy, the Environment and Water. Staff in the Science Program 
supported the smooth administration of the Assessment despite the many challenges that arose 
during the project years. 

A long list of expert reviewers provided advice that improved the quality of our methods report, 
the various technical reports, the catchment report and the case study report. The Governance 
Committee and Steering Committee (listed on the verso pages) provided important input and 
feedback into the Assessment as it progressed. 

Finally, the complexity and scale of this Assessment meant that we spent more time away from 
our families than we might otherwise have chosen. The whole team recognises this can only 
happen with the love and support of our families, so thank you. 

 

Some of the CSIRO staff involved in field work in northern Australia water resource assessments who applied their 
experience to the Southern Gulf analyses 

Photo: CSIRO – Nathan Dyer 

 



Contents 

Director’s foreword .......................................................................................................................... i 
Key findings for the Southern Gulf catchments .............................................................................. ii 
Overview of the Southern Gulf catchments ....................................................................... vi 
Indigenous values, rights and development goals .............................................................. x 
Opportunities for agriculture and aquaculture .................................................................. xi 
Other existing and potential industries that depend on water....................................... xvii 
The Southern Gulf catchments have productive groundwater systems .......................... xix 
Changes in volumes and timing of river flows have ecological impacts .......................... xxi 
Commercial viability and other considerations .............................................................. xxiii 
The Southern Gulf Water Resource Assessment Team .............................................................. xxvi 
Acknowledgements .................................................................................................................... xxvii 
Part I Introduction and overview 1 
1 Preamble ............................................................................................................................. 2 
1.1 Context .................................................................................................................. 2 
1.2 The Southern Gulf Water Resource Assessment .................................................. 4 
1.3 Report objectives and structure ............................................................................ 9 
1.4 Key background ................................................................................................... 12 
1.5 References ........................................................................................................... 16 
Part II Resource information for assessing potential development opportunities 18 
2 Physical environment of the Southern Gulf catchments ................................................. 19 
2.1 Summary .............................................................................................................. 20 
2.2 Geology and physical geography of the Southern Gulf catchments ................... 22 
2.3 Soils of the Southern Gulf catchments ................................................................ 31 
2.4 Climate of the Southern Gulf catchments ........................................................... 46 
2.5 Hydrology of the Southern Gulf catchments....................................................... 60 
2.6 References ........................................................................................................... 94 
3 Living and built environment of the Southern Gulf catchments .................................... 101 
3.1 Summary ............................................................................................................ 102 
3.2 Southern Gulf catchments and their environmental values ............................. 106 
3.3 Demographic and economic profile .................................................................. 133 
3.4 Indigenous values, rights, interests and development goals ............................ 169 
3.5 Legal and policy environment ........................................................................... 182 
3.6 References ......................................................................................................... 186 
Part III Opportunities for water resource development 205 
4 Opportunities for agriculture in the Southern Gulf catchments .................................... 206 
4.1 Summary ............................................................................................................ 207 
4.2 Land suitability assessment ............................................................................... 212 
4.3 Crop and forage opportunities in the Southern Gulf catchments .................... 217 
4.4 Crop synopses .................................................................................................... 245 
4.5 Aquaculture ....................................................................................................... 279 
4.6 References ......................................................................................................... 292 
5 Opportunities for water resource development in the Southern Gulf catchments ...... 296 
5.1 Summary ............................................................................................................ 297 
5.2 Introduction ....................................................................................................... 301 
5.3 Groundwater and subsurface water storage opportunities ............................. 302 
5.4 Surface water storage opportunities ................................................................ 323 
5.5 Water distribution systems – conveyance of water from storage to crop ....... 366 
5.6 References ......................................................................................................... 373 
Part IV Economics of development and accompanying risks 378 
6 Overview of economic opportunities and constraints in the Southern Gulf catchments 
........................................................................................................................... 379 
6.1 Summary ............................................................................................................ 380 
6.2 Introduction ....................................................................................................... 381 
6.3 Balancing scheme-scale costs and benefits ...................................................... 383 
6.4 Cost–benefit considerations for water infrastructure viability ......................... 399 
6.5 Regional-scale economic impact of irrigated development ............................. 408 
6.6 References ......................................................................................................... 414 
7 Ecological, biosecurity, off-site and irrigation-induced salinity risks ............................. 417 
7.1 Summary ............................................................................................................ 418 
7.2 Introduction ....................................................................................................... 422 
7.3 Ecological implications of altered flow regimes ................................................ 424 
7.4 Biosecurity considerations ................................................................................ 451 
7.5 Off-site and downstream impacts ..................................................................... 467 
7.6 Irrigation-induced salinity.................................................................................. 474 
7.7 References ......................................................................................................... 478 
Appendices 495 
........................................................................................................................... 496 
Assessment products ...................................................................................................... 496 
........................................................................................................................... 499 
Shortened forms ............................................................................................................. 499 
Units ........................................................................................................................... 502 
........................................................................................................................... 503 
List of figures ................................................................................................................... 503 
List of tables .................................................................................................................... 512