National Groundwater Resources and

A series of water resources assessments were conducted in Australia, with a primary focus on surface water. These assessments included:

• a review of Australia's Water Resources (1975), Australian Water Resources Council (1976), resulting among other outputs in 'Australian Rainfall and Runoff', a key work on hydrological data and methods in the continent;

• first national survey of water use in Australia (1981), Department of National Development;

• a review of Australia's Water Resources (1985), Australian Water Resources Council (1987);

• Water and the Australian Economy (AATSE) (1999);

• Water Account for Australia, Australian Bureau of Statistics (2000);

• National Land and Water Resources Audit (NLWRA) (2000), update of AWRC (1985).

Most of these studies were complemented by detailed hydrogeological and water resources assessments in the states, but had historically focused on resource development, and there was little information on actual groundwater use. The NLWR. A provides the most comprehensive national overview of groundwater availability and use in Australia to date. It estimated that the national groundwater availability amounts to 25.78 billion cubic metres per year on average, of which 21 billion cubic metres is of potable quality (NLWRA, 2002). Total abstraction in 1996/97 amounted to less than 10% of this at 2.49 billion cubic metres. On the face of it, this does not look to be a problem. However, poor distribution of groundwater use across available resources has resulted in overallocation of many good-quality and readily accessible groundwater stores - often the alluvial plains of prior and existing riverbeds within which surface water irrigation districts lie. The sustainable yield of groundwater in each state is shown in Table 15.1 and is disaggregated by salinity status, showing that about 63% is of high quality. It shows that salinity concerns are greatest in Victoria, western Australia and south Australia (SA). Salinity problems are on the rise in specific localities in NSW.

Nationally, about 50% of total groundwater abstraction is for irrigated agriculture (Table 15.2), but this figure rises to 65% in Victoria and NSW and is highest in SA at 80%. Groundwater allocation is a little over one-fourth of the total national water resources availability and less than one-third of the surface water allocation. The available resource in Northern Territories (NT) (Table 15.2) is enormous compared with actual allocation, so the fact that actual use exceeds allocation is not necessarily significant in resource management terms. The same story is broadly true for Tasmania. Rural water use includes stock and domestic water provision, and the majority of water abstracted from the Great Artesian Basin (covering large parts of NSW, Queensland and NT) is for pastoral use. A detailed breakdown of groundwater use is available for 286 out of 538 groundwater management units across the nation, and summary data are available for 377 of them. Groundwater is the sole source of water for many rural towns, mines and associated settlements.

Many surface-irrigated properties in northern Victoria and throughout NSW also have bores as drought insurance and for supplementing surface water supplies. Generally they abstract from deeper, higher-quality aquifers, which are separated from saline layers by an aquitard. Nevertheless, some provide water of suboptimal quality which is mixed with surface water before being applied to the crop (known colloquially as 'shandying').

In many areas, actual use is significantly less than allocation (Table 15.3). However, the local balance of use and conservation can be highly variable between years.

Table 15.1. Sustainable yield, by salinity status, of groundwater in Australia. (From National Land and Water Audit, 2002.)

<500

5001 ,000

1 ,000-1 ,500

1,5003,000

3,0005,000

5,00014,000

>14,000

Total

NSW

554

4,237

1 29

790

480

-

-

6,189

VIC

302

422

244

367

207

1,377

797

3,717

QLD

1,422

1,030

113

160

35

23

-

2,784

WA

514

1 ,1 62

1,150

1 ,500

766

841

371

6,304

SA

-

290

709

102

21

25

-

1 ,1 46

TAS

1,585

767

-

178

-

-

-

2,531

NT

5,785

1 86

324

1 41

5

-

-

6,441

ACT

103

-

-

-

-

-

-

1 03

Total

10,264

8,094

2,670

3,238

1 ,51 5

2,266

1 ,1 68

29,215

%

35

28

9

11

5

8

4

1 00

Table 15.2. Mean annual groundwater extraction by category of use (million). (From National Land and Water Audit, 2002.)

Irrigation

Urban/industrial

Rural

In situ

Total

NSW

643

160

205

0

1 008

VIC

431

1 27

54

10

622

QLD

816

265

541

0

1 622

WA

280

821

37

0

1 1 38

SA

354

23

42

24

430

TAS

9

7

4

0

20

NT

47

48

33

0

1 28

ACT

2

0

3

0

5

Total

2003

1 370

788

34

41 71

Table 15.3. Total annual water allocations in Australia, in MCM. (From National Land and Water Audit, 2002.)

Surface

Ground

Total

water

water

Total

water

A allocation -

% difference

allocation

allocation

allocation

use

use

allocation-use

NSW

9,825

2,665

12,490

10,004

2,486

25

VIC

5,469

780

6,249

5,788

-461

7

QLD

3,202

983

4,185

4,591

406

-9

WA

855

1 ,1 38

1 ,993

1 ,796

1 97

10

SA

740

630

1 ,370

1 ,266

1 04

8

TAS

403

20

423

471

-48

-11

NT

53

73

1 26

179

-53

-42

ACT

76

7

83

73

10

12

Total

20,623

6,296

26,919

23,280

3,639

16

While groundwater development in western Australia, NT and the Australian Capital Territory is dominated by priority (town supply, stock and domestic) uses, intermittent surface flows have resulted in the agricultural development of groundwater as a primary agricultural source in many parts of SA. SA is also distinguished by the security of its surface water supply via the Murray River, which is a volume secured in agreement with Victoria, NSW and the Commonwealth (case study 1). This allows SA much tighter accounting mechanisms than can be accommodated by the less certain water budgets of other states.

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