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Total water resource
Previous studies, including Australian Water Resources Assessment 2000 (NLWRA 2001) and Water Account, Australia, 2000–01, have presented the water resource as a ‘water stock’, which is the sum of mean annual runoff and sustainable groundwater yield. To this can be added the total volume of water already in storage across Australia at the start of the reporting year (July 2004), to describe a total water resource for Australia in 2004–05. It should be noted that 2000-01 figures used in the Water Account, Australia, 2004-05 have been updated since publication of the previous Water Account, and therefore may be different.
Water runoff, groundwater deep drainage, and evapotranspiration data were provided by the Bureau of Rural Sciences as part of the Water 2010 project. Modelling methods were used to estimate runoff, deep drainage and evapotranspiration.
Total water resource by jurisdiction in Australia in 1996-97 and 2004–05
| Inflows 2004-05 - Runoff (GL) |
149 |
30,266 |
47,151 |
93,018 |
1,285 |
32,084 |
14,266 |
24,560 |
242,779 |
| Inflows 2004-05 - Deep drainage (GL) |
29 |
7,133 |
8,382 |
13,599 |
2,925 |
1,228 |
2,695 |
13,182 |
49,174 |
| Total inflows 2004-05 (GL) |
178 |
37,399 |
55,533 |
106,618 |
4,210 |
33,312 |
16,961 |
37,742 |
291,953 |
| Volume in storage of large dams as at 1 July 2004 (GL) |
78 |
7,970 |
251 |
6,287 |
111 |
13,744 |
4,371 |
11,352 |
44,164 |
| Total water resource 2004-05 (GL) |
256 |
45,369 |
55,784 |
112,905 |
4,321 |
47,056 |
21,332 |
49,094 |
336,117 |
| Water stock 1996-97 (GL) |
520 |
47,841 |
80,905 |
159,902 |
3,916 |
48,113 |
23,544 |
50,357 |
415,097 |
| Total water resource 2004-05 as a proportion of water stock 1996-97 |
49% |
95% |
69% |
71% |
110% |
98% |
91% |
97% |
81% |
Note: Water stock 1996-97 data are based on NLWRA (2001) combined with new data supplied to the Australian Bureau of Statistics by Western Australian and Northern Territory government water management agencies.
Nationally, total inflows were estimated to be 291,953 gigalitres for the 2004–05 year, which includes a total surface water runoff of 242,779 gigalitres and groundwater recharge of 49,174, gigalitres. The volume stored in large dams was 44,164 gigalitres as at 1 July 2004, making a total water resource estimate for Australia of 336,117 gigalitres.
The total water resource figure is approximate, as it includes only modelled runoff and deep drainage data and data on large dams. Other water resource data that have not been included, are the capacity and levels of farm dams and other minor storages, this is because the data for these items are mostly unavailable.
The total water resource figure of 336,117 gigalitres in 2004–05 was 81 per cent of the water stock in 1996-97 (NLWRA 2001). A combination of two factors may explain the data differences: (i) that water resource availability during 2004–05 was lower than during the late 1990s; and (ii) differences in calculation methods may have contributed to this discrepancy. Rainfall, runoff and recharge have all been below average for a number of years, which have led to an increased demand to access stored water.
In relation to the differences in methods, NLWRA did not recognise the close interaction of surface water and groundwater resources. As a result, ‘double counting’ of the water resource (i.e. counting a parcel of water as contributing to both surface water yields and groundwater yields) was recognised as an issue that was not adequately addressed in NLWRA, which may have led to over-estimating of the quantity of the resource in that report.
.jpg) Murray River at Nildottie, South Australia
Image by Philip Engler, sourced from SKM
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