Water resources and management overview ... - NSW Office of Water

Water resources and management overview

Lower Darling River Catchment

www.water.nsw.gov.au

Publisher NSW Department of Primary Industries, Office of Water. Level 18, 227 Elizabeth Street GPO Box 3889 Sydney NSW 2001 T 02 8281 7777 F 02 8281 7799 [email protected] www.water.nsw.gov.au

The NSW Office of Water manages the policy and regulatory frameworks for the state’s surface water and groundwater resources, to provide a secure and sustainable water supply for all users. It also supports water utilities in the provision of water and sewerage services throughout New South Wales.

Water resources and management overview: Lower Darling River Catchment May 2012 ISBN 978 0 7313 3532 9

This report may be cited as: Green D., Ali A., Petrovic J., Burrell M., Moss P. (2012) Water resources and management overview: Lower Darling River Catchment, NSW Department of Primary Industries, Sydney

Cover photo: Aerial view of the Lower Darling River, May 2010

© State of New South Wales through the NSW Department of Trade and Investment, Regional Infrastructure and Services, 2012 This material may be reproduced in whole or in part for educational and non-commercial use, providing the meaning is unchanged and its source, publisher and authorship are clearly and correctly acknowledged. Disclaimer: While every reasonable effort has been made to ensure that this document is correct at the time of publication, the State of New South Wales, its agents and employees, disclaim any and all liability to any person in respect of anything or the consequences of anything done or omitted to be done in reliance upon the whole or any part of this document.

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Water resources and management overview: Lower Darling River catchment

Contents 1

The Lower Darling catchment.................................................................................................... 1

2

Climate.......................................................................................................................................... 4 2.1 Rainfall ................................................................................................................................ 4 2.2 Evaporation ......................................................................................................................... 5

3

Land use....................................................................................................................................... 6

4

Environment ................................................................................................................................ 8 4.1 Native vegetation ................................................................................................................ 8 4.2 Parks and reserves ............................................................................................................. 8 4.3 Wetlands ............................................................................................................................. 9 4.4 Significant biodiversity ...................................................................................................... 10

5

Surface water............................................................................................................................. 11 5.1 The Darling River .............................................................................................................. 11 5.2 Great Darling Anabranch .................................................................................................. 12 5.3 Streamflow characteristics ................................................................................................ 12

6

Groundwater .............................................................................................................................. 15

7

River operations and management ......................................................................................... 17 7.1 Major storages and regulating structures ......................................................................... 17 7.2 Murray-Darling Basin Agreement...................................................................................... 20 7.3 Licensed water use ........................................................................................................... 20 Surface water .................................................................................................................... 20 Groundwater ..................................................................................................................... 21 7.4 Water sharing plans .......................................................................................................... 22 Surface water sharing plans ............................................................................................. 22 Surface and groundwater.................................................................................................. 23 Groundwater plans............................................................................................................ 24

8

References ................................................................................................................................. 26

i | NSW Office of Water, May 2012


Tables Table 1: Land use in the Lower Darling catchment............................................................................... 6 Table 2: Threatened aquatic species of the Lower Darling River ....................................................... 10 Table 3: Mean daily flow for selected Lower Darling gauges.............................................................. 12 Table 4 - Menindee Lakes Storage Details ......................................................................................... 17 Table 5: Surface water share components for the Lower Darling catchment 2010–11 ...................... 20 Table 6: Groundwater share components for the Lower Darling catchment 2010-11 ........................ 22

Figures Figure 1: The Menindee Lakes and Lower Darling catchment.............................................................. 2 Figure 2: Topography and elevation of the Lower Darling catchment .................................................. 3 Figure 3: Average annual rainfall in the Lower Darling catchment ....................................................... 4 Figure 4: Mean monthly rainfall at Menindee 1876–2010 ..................................................................... 4 Figure 5: Average annual pan evaporation in the Lower Darling catchment ........................................ 5 Figure 6: Average daily evaporation at Broken Hill 1995–2010 ............................................................ 5 Figure 7: Land use in the Lower Darling catchment.............................................................................. 7 Figure 8: Annual flow in the Darling River at Weir 32 1959–2010 ...................................................... 13 Figure 9: Hydrograph of daily flows and cumulative deviation from the mean for Weir 32 1958-2011 ....................................................................................................................... 14 Figure 10: Groundwater aquifers of the Lower Darling catchment ..................................................... 15 Figure 11: Groundwater Management Areas of the Lower Darling catchment.................................. 16 Figure 12: The Menindee Lakes Scheme ........................................................................................... 17

ii | NSW Office of Water, May 2012


1 The Lower Darling catchment The Darling River is located in the semi-arid environment western New South Wales. The ‘Lower Darling’ commonly refers to that portion of the Darling River which is regulated by releases from the Menindee Lakes Scheme, near the township of Menindee downstream to its junction with the Murray River at Wentworth, 530 km downstream (Figure 1). The general topography of the catchment is flat with elevations across most of the floodplain area being less than 100 metres (Figure 2). Land use is dominated by grazing with smaller areas of cropping occurring in the southern half of the catchment and on some of the region’s lake beds. Prior to construction of the Menindee Lakes Scheme the Lower Darling River was unregulated, and like the unregulated portion of the catchment above Menindee, it was subject to highly variable flow conditions. With completion of the scheme in 1960 the flow regime of the river was altered significantly, with reduced monthly flow volumes, long periods of constant low flow and reduced frequency of small to medium sized flow events (Green et al. 1998) A major feature of the Lower Darling is the Great Darling Anabranch and its series of large overflow lakes. Once filled, the ephemeral lakes of the Anabranch hold water for extended periods of time making the area highly productive and important as waterbird habitat. Prior to European settlement the Lower Darling was occupied by the Barkindji people. They called the river the ‘Barka’ and their homelands ranged along the riverine plains from Wentworth up to Wilcannia. The region is rich in Aboriginal heritage, and the river and its lakes remain important cultural sites for the local indigenous population. Today the Lower Darling catchment supports a very sparse rural population. The main urban centres are Wentworth in the south (population 1,300), Menindee in the north (population 330) and the small village of Pooncarie (population 48) which nestles by the river midway between Menindee and Wentworth.

River red gums along the Great Darling Anabranch

1 | NSW Office of Water, May 2012


Figure 1: The Menindee Lakes and Lower Darling catchment



Figure 2: Topography and elevation of the Lower Darling catchment



2 Climate 2.1 Rainfall The Lower Darling region receives some of the lowest rainfall in NSW. Annual rainfall averages just 220 to 280 mm across most of the catchment with a gradient of increasing rainfall occurring from north-west to the south-east (Figure 3). At Menindee the rainfall is distributed fairly evenly across the year with monthly rainfall averaging from 16 to 23 mm (Figure 4). Figure 3: Average annual rainfall in the Lower Darling catchment

Source: Hutchinson and Kesteven 1998

Figure 4: Mean monthly rainfall at Menindee 1876–2010

Source: Bureau of Meteorology Climate Data Online



2.2 Evaporation High summer temperatures result in very high evaporation rates across the Lower Darling catchment. Class A pan evaporation increases from around 1,900 mm in the south-east to 2,100 mm in the northwest (Figure 5). No stations record evaporation within the catchment. However data for Broken Hill (north-west of Menindee) shows that daily evaporation rates in the north of the catchment are highly seasonal ranging from 2 mm per day in winter up to 13 mm per day in summer (Figure 6). Figure 5: Average annual pan evaporation in the Lower Darling catchment

Source: Hutchinson and Kesteven 1998

Figure 6: Average daily evaporation at Broken Hill 1995–2010

Source: Bureau of Meteorology Climate Data Online



3 Land use Grazing accounts for over 90 per cent of the land use in the Lower Darling catchment. Small areas of dryland cropping occur in the southern portion of the catchment and there is some minor irrigation development around Wentworth (Figure 7 and Table 1). Some of the lake beds in the catchment are used permanently or opportunistically for cropping. Lake Tandou was previously part of the Menindee Lakes system but has been under permanent cultivation since 1972. Cotton, wheat and barley are grown under rotation with other crops including sorghum, corn, soybeans, sunflowers, chickpeas and canola (Tandou Limited 2007). The lakes of the Great Darling Anabranch are also subject to cropping when they are dry. Table 1: Land use in the Lower Darling catchment 2 Area (km )

Proportion of area (%)

Grazing

31,608

91.5

Lakes, rivers, dams

1,333

3.9

Native landscapes

652

1.9

Conservation

634

1.8

Forestry

157

0.5

Dryland cropping and horticulture

106

0.3

Wetlands

17