Australian Natural Resources Atlas

Natural Resource Topics

Salinity - Risk and Hazard - New South Wales

New South Wales

Location map

Where is there a dryland salinity risk or hazard and how was this determined?

New South Wales Areas of High Risk of Dryland Salinity

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 trialled 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.

Areas affected are based on groundwater levels and air photo interpretation. The methodology applied for NSW is documented in Appendix 1 of NSW Dryland Salinity Assessment 2000 Report. The merged data, at a nominal scale of 1:250 000, shows actual areas where dryland salinity or water tables <2m below the surface have been measured. For current extent, every delineated area is underpinned by either air photo data or by one or more groundwater bores. There is high confidence in the accuracy of each of the delineated areas shown in the map above. It must be acknowledged that there will be other areas currently affected by dryland salinity. These have not been identified due to a combination of the inadequacies in the spatial coverage of available data and the currently available methods to spatially generalise water table maps from point data. Therefore, the area at risk is regarded as conservative. A number of techniques to spatially extrapolate these data to infer potential areas at risk were trialed but were considered scientifically or statistically invalid or data limited. All assessments of risk in this report are based on the criteria that each area at risk has groundwater levels of < 2 m below the surface. An assessment based on groundwater < 5 m and rising was considered inappropriate because it would result in disproportionate areas being identified as currently at risk. Those areas currently at 5m and rising were considered at risk in the short to medium terms and hence, would likely be included in the areas forecasted at risk in 2020 or 2050.

In areas that were spatially data rich, there is high confidence in the data presented in the map above. A major area with limited data was the Gwydir catchment. According to the analyses presented in this report, there are no areas currently affected by dryland salinity in the Gwydir. This is simply due to limited data available for these analyses. Therefore, the predictions in this report, particularly for the Gwydir catchment should be seen as conservative under-predictions of the true current status of dryland salinity in NSW.

Groundwater trends

The forecasted areas of risk for 2020 and 2050 are based on water table rises calculated from a network of monitored groundwater bores in NSW. These are fully described in Appendix 1 and are summarised as catchment average water table rises in the table below.

Highest rates of rise are evident for the southernmost catchments in NSW. Rates of water table rise tend to decrease in a northerly direction. This suggests that the impacts of rising water tables will take longer to surface in the northernmost catchments of NSW. High rates of water table rise for the southern catchments is one factor explaining the larger extent of current shallow water tables and dryland salinity in southern NSW.

Table: Catchment average rates of water table rise from monitored bore data.
Catchment Rise (m/yr)
Murray 0.15
Murrumbidgee 0.14
Lachlan 0.11
Macquarie 0.09
Castlereagh 0.11
Namoi 0.06
Gwydir 0.04
Macintyre -0.01

How can dryland salinity risk change over time?

New South Wales Salinity Risk Map 2050

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 trialled 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.

Maps depicting the forecasted extent of dryland salinity in the years 2020 and 2050 reveal large areas of future shallow water tables, particularly in the Murray, Murrumbidgee, Castlereagh and Macintyre catchments.

Area of land affected by depth of water tables less than 2m, 5m and 10m, have been calculated for the major catchments of the eastern Murray-Darling Basin. There are large increases in areas affected by shallow water tables for all eastern Murray-Darling Basin catchments. The largest increases are within the Murrumbidgee, Murray and Castlereagh catchments. The large areas estimated with water tables less than 5m below the surface in 2050, indicates a continuing risk into the longer term. Assuming the current risk is based on a criterion of depth to water table less than 2m, there is approximately 150 000 ha of land currently affected in the eastern catchments of the Murray-Darling Basin. If an alternative criterion of less than 5m and rising is considered, this increases to over 560 000 ha currently affected. This indicates the sensitivity of the results to changes to just one of the criteria used to ascertain current risk. All analyses undertaken in this study have been designed to ensure that results err on the side on conservatism.

Table: 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/anot available

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 below).

Table: 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

Further information

New South Wales Dryland Salinity Assessment 2000

Link to Map maker to make a map using this information.

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