New South Wales

Approximately 180 000 ha of land have shallow watertables or are affected by dryland salinity in New South Wales. Over 90% occurs in five catchments - the Murray, Murrumbidgee, Lachlan, Macquarie and Hunter rivers. The Hunter and Hawkesbury-Nepean river catchments have the most extensive areas of existing dryland salinity or shallow groundwaters of New South Wales in coastal catchments.

Within the Murray Darling Basin, the area predicted to be at risk will increase from approximately 152 000 ha to 1.3 million hectares by 2050, a greater than eight-fold increase.

Figure 3. Dryland Salinity Risk in New South Wales 2000

Areas of risk are based on groundwater levels and air photo interpretation. The merged data, at a nominal scale of 1:250 000, show actual areas where dryland salinity or watertables less than 2 m have been measured. For the extent map, every delineated area is underpinned by either air photo data or by one or more groundwater bores. Therefore, the area at risk is regarded as conservative due to limitations in the spatial coverage of air photo and bore data. A number of techniques to spatially extrapolate these data to infer potential areas at risk were trialed but were considered scientifically or statistically inadequate. Estimates of impacts are based on areas at risk having groundwater levels of less than 2 m. An impact assessment based on groundwater less than 5 m and rising was considered inappropriate. Total areas affected with groundwater less than 5 m and rising have been presented, but only for improved consistency with other States.

Coastal catchments are not represented in the prediction for 2050 due to the paucity of groundwater data on which to make the estimates.

Figure 4.Dryland salinity risk in New South Wales in 2050

Dryland salinity risk in New South Wales 2050.

Table 5.Estimated areas (ha) with depth of watertable less than 2 m under current conditions and year 2020 and year 2050 scenarios for major catchments of the Murray Darling Basin and coastal catchments.

Catchment	2000	2020	2050
Lake Hume	127	3 973	19 254
Murray	39 526	168 978	293 191
Murrumbidgee	58 098	286 848	469 500
Lachlan	19 793	38 845	153 264
Macintyre	3 800	25 500	67 224
Gwydir	0	0	2 973
Namoi	2 896	4 288	27 837
Castlereagh	1 197	12 005	174 666
Macquarie	25 072	36 767	90 848
Richmond	155	n/a	n/a
Clarence	91	n/a	n/a
Bellinger	27	n/a	n/a
Manning	34	n/a	n/a
Hunter	22 954	n/a	n/a
Hawkesbury-Nepean	4806	n/a	n/a
Georges-Cooks	13	n/a	n/a
Deua	11
Total	180 600	579 224	1 300 807

n/a = not available

Table 6.Estimated areas (ha) affected by depth to less than 5 m with a rising watertable trend for eastern Murray Darling Basin catchments.

Catchment	2000	2020	2050
Lake Hume	3 973	12 999	37 496
Murray	168 978	227 187	293 514
Murrumbidgee	156 319	483 300	997 058
Lachlan	72 726	153 105	294 524
Macintyre	24 259	63 871	127 385
Gwydir	661	10 024	24 169
Namoi	10 244	20 427	57 528
Castlereagh	12 015	110 396	243 245
Macquarie	47 548	106 856	324 974
Total	496 722	1 188 163	2 399 892

The best available estimates of rates of groundwater rise indicate that by 2020 rising watertables will occur in large areas of the Murrumbidgee and Murray catchments. By 2050, large areas of the Lachlan, Castlereagh and Macintyre catchments will also be affected (Tables 5 & 6).

Assuming no change in management and a continuation of similar climate variability to that observed during the assessment period, salt loads are predicted to increase during the next 50 years for many catchments (Table 7). The most marked increases in total salt loads for the major inland rivers in New South Wales are predicted for the Lachlan, Murrumbidgee and Namoi Rivers. The Bogan, Macquarie and Namoi catchments showed the largest increase in salinity (e.g. water salinity in the Bogan River is predicted to rise from its current level of approximately 700 µS/cm electrical conductivity to almost 2000 µS/cm in 2050; the Macquarie River rises from approximately 600 to 1700 µS/cm over the period). These predicted values exceed the World Health Organization's recommended limit for potable drinking water (800 µS/cm).

Table 7.Redistribution of salt load in the landscape by catchment.

Catchment	Median salt load (tonnes per year)
	2000	2020	2050
Macintyre at Mungindi	68 000	68 000	68 000
Gwydir near Collarenebri	6 600	7 000	8 500
Namoi at Goangra	50 000	81 000	100 000
Barwon Darling at Menindee	132 500	215 000	265 000
Castlereagh at end-of-valley	18 400	20 100	36 500
Macquarie at Carinda	32 100	65 500	89 000
Bogan at Gongolgon	24 600	48 000	63 500
Lachlan at Forbes	234 800	290 500	428 300
Murrumbidgee at Balranald	139 000	166 500	180 500

Findings

Table 8.Key assets at risk from shallow watertables within the catchments of the Murray Darling Basin and the coastal catchments of the Hunter and Hawkesbury-Nepean rivers*, New South Wales.

Assets	2000	2020	2050
Cropping land (ha)	28 700	114 445	223 658
Forests (ha)	540	15 348	34 507
Horticulture land (ha)	1000	1 913	4 780
Managed protection areas (ha)	130	186	744
Nature conservation areas (ha)	2400	9 450	35 502
Pasture land (ha)	132400	412 125	927 171
Remnant vegetation (ha)	5 300	17 370	46 514
Built-up areas (ha)	1 182	2 209	3 646
Towns (number)	38	82	125
Highways (km)	130	331	534
Major roads (km)	110	298	701
Minor roads (km)	700	1 959	3 615
Railways (km)	100	226	416
Bridges (number)	20	22	43
Wetlands (directly affected) (number)	9	1	2

* Data for the Hunter and Hawkesbury-Nepean only for 2000.

Groundwater trends are dominated by rising or stable trends. No groundwater flow system under dryland agricultural systems has a significant falling trend.
Large areas of the Western Slopes, the Hunter Valley and the Sydney Basin already have saline groundwater within 2 m of the surface.
Within the Murray Darling Basin, areas affected by shallow watertables will increase
four-fold over the next 20 years, and eight-fold over by 2050.
Of the 152 000 ha of land at risk from shallow groundwater within the Murray Darling Basin, 93% is agricultural land.
The area of agricultural land within the Murray Darling Basin that is affected by shallow watertables will increase from the current 142 000 ha to almost 1.2 million hectares by 2050.
Forecasted scenarios indicate that areas of conservation and remnant vegetation affected by shallow watertables will increase twelve-fold over the next 50 years.
Areas of forest affected by shallow watertables could potentially increase seventy-fold over the next 50 years.
In-stream saltloads are forecast to increase by at least a factor of two in most Murray Darling Basin catchments by 2050. In some catchments, it is predicted that river EC levels will more than exceed international drinking water guidelines.
An estimated 954 ha of built-up areas within the Murray Darling Basin are affected by shallow watertables. This could increase to over 3600 ha by 2050.

Key issues

Development of acceptable and achievable performance targets for major catchments contributing to dryland salinity will be a major challenge. This will require very considerable technical and process support to regional community groups.
Development of economically viable and socially acceptable management options for many areas will be extremely difficult because of the nature of the groundwater systems controlling the salinity.

Government responses

The New South Wales Government released its State Salinity Strategy in August 2000. The strategy provides an integrated framework for salinity management in New South Wales. It advocates a shared responsibility involving land managers, conservationists, Aboriginal communities, scientists, businesses and all levels of government. Key tools are:

development of end-of-valley salinity targets that reflect the salinity levels the community is prepared to accept and can afford to live with;
establishment of market-based solutions to encourage strategic investment and provide land managers with an incentive to manage their properties for specific environmental outcomes, such as reduced salinity;
introduction of a Salinity Business Development Program to encourage emerging industries that can use saline land productively;
better use of regulatory tools (e.g. incorporating salinity impact assessment into the clearing application approval process, water licensing and environmental planning instruments);
improvement in the ability of front-line staff to provide advice to land managers;
investment in upgrading data and analytical tools, and in ensuring that information is user-friendly and accessible;
undertaking and facilitating research into land use systems that minimise recharge, use of saline-affected land and water, impacts of salinity on natural ecosystems and social and economic issues; and
improvement of the focus of catchment management planning systems through catchment management boards to manage for change at the appropriate geographical scales.

Table of Contents for the Australian Dryland Salinity Assessment 2000

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