Indicator: IW-05 Average annual groundwater depth

Data

Groundwater resources of the Murray Basin
Location	Approx aquifer depth	Estimated sustainable volume, ML/year	Estimated current usage, ML/year	Average quality, mg/L	Range of usage quality, mg/L
NSW - Southern Riverine Plain, Murray	Shallow	400 000	30 000	<1 000	100 - 7 000
NSW - Southern Riverine Plain, Murray	Deep			<1 000	200 - 5 000
NSW - Mid-Riverine Plain, Murrumbidgee	Shallow	650 000	140 000	<1 000	100 - 7 000
NSW - Mid-Riverine Plain, Murrumbidgee	Deep			<1 000	100 - 5 000
NSW - Nth'n Riverine Plain, Lachlan	Shallow	330 000	26 000	-	-
NSW - Nth'n Riverine Plain, Lachlan	Deep			<1 000	100 - 3 500
NSW - Darling River, Alluvium	Shallow	uncertain	500	<1 000	100 - 7 000
VIC - Riverine Plain	Shallow	200 000	70 000	1000	500 - 3 000
VIC - Riverine Plain	Deep	40 000	20 000	1000	300 - 1 500
VIC - Mallee and Wimmera	Deep	50 000	5 000	1 000	800 - 3 000
VIC - Grampians fringes	Shallow	4 000	100	1 500	500 - 3 000
SA - Coastal plain	Shallow	40 000	36 000	1 500	1 000 - 4 000
SA - Mallee	Deep	100 000	34 000	1 500	800 - 7 000

Source: Groundwater Working Group 1996, Groundwater Development Potential in the Murray Basin, Technical Report No.1, Murray-Darling Basin Commission, Canberra, viewed 23 Mar 2005, http://www.mdbc.gov.au/nrm/water_management/groundwater, p. 4, cited in Murray-Darling Basin Commission, Groundwater Resources, Table 5

Sustainable yield groundwater, by level of salinity - 2000
Level of salinity	NSW	Vic	Qld	SA	WA	Tas	NT	Aust
Volume (ML) Less than 1500 mg/L Less than 500 mg/L 500–1000 mg/L 1000–1500 mg/L Total	698 215 3 927 969 34 000 4 660 184	193 560 827 000 386 357 1 406 917	1 373 040 994 530 119 460 2 487 030	55 850 228 640 679 515 964 005	1 898 876 1 061 380 995 171 3 955 427	1 585 388 766 705 449 2 352 542	4 412 001 287 238 454 972 5 154 211	10 216 930 8 093 462 2 669 924 20 980 317
1500 mg/L and over 1500–3000 mg/L 3000–5000 mg/L 5000–14000 mg/L More than 14000 mg/L Total	812 450 1 550 440 400 — 1 254 400	243 735 707 133 200 750 797 000 1 948 618	113 540 29 750 62 730 — 206 020	252 645 600 761 900 — 1 015 145	1 467 640 588 568 841 195 370 668 3 268 071	178 230 — — — 178 230	139 306 182 917 — — 322 22	3 207 547 1 510 518 2 306 975 1 167 668 8 192 707
Total sustainable yield	5,914,584	3,355,535	2,693,050	1,979,150	7,223,498	2,530,772	5,476,434	29,173,024
Proportion (%) Less than 1500 mg/L 1500 mg/L and over	79 21	42 58	92 8	49 51	55 45	93 7	94 6	72 28

Source: Australian Bureau of Statistics 2004, Water Account Australia 2000-01, Cat. No. 4610.0, Australian Bureau of Statistics, Canberra, viewed 9 Nov 2005, http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/D828F04237840B07CA256F4C007155B3, Table 10.10, p. 98

What the data mean

Data on depth of groundwater is unavailable. Groundwater sustainable yield data reported in 2001 show that there are approximately 29 173 gigalitres of groundwater available in Australia but it is not all of equal quality. Dissolved salt concentrations vary and determine the suitability of water use, eg a salinity level above 1500 mg/L is not suitable for irrigation.

Data Limitations

Data on depth of groundwater are unavailable. Groundwater sustainable yield data is reported as an alternative measure of availability of groundwater for human use, but does not provide insight into the pressure of rising groundwater on the land, biodiversity or surface waters.

Groundwater sustainable yield data was reported in 2001 but has not been updated, so there are currently no trend data on availability of groundwater for human use.

Variations in calculating sustainable yields occur between States and Territories.

Issues for which this is an indicator and why

Inland Waters - Catchment scale influences - Hydrological condition - Ground-water availability and human use

Depth to a groundwater resource is an important factor in determining the feasibility of developing the resource and is therefore a surrogate indicator for availability of the resource for human use as well as a direct indicator for the pressure of rising or falling groundwater on land and biodiversity. Groundwater levels fluctuate naturally with the seasons and in some aquifers fluctuate due to the high recharge rates, low storativity of the aquifer and extractions. Many of the good quality groundwater aquifers in Australia are highly developed, with some having falling levels due to over-extraction. In other areas with falling levels, drought conditions over the last few years are the cause. Groundwater levels do not respond immediately to recharge, and so the effects of drought or over-extraction may occur years after the stress on the system.

Salinity and waterlogging problems can occur where watertables have risen to near the ground surface due to vegetation clearing. This can reduce the availability of groundwater for both human and natural uses, as well as increasing surface salt with consequential impacts on land, surface waters and biodiversity.

In the absence of data on groundwater depth, estimates of sustainable yield are reported as a measure of availability of groundwater for human use. Sustainable yield is the level of extraction measured over a specified planning time frame that should not be exceeded to protect the higher value social, environmental and economic uses associated with the aquifer. Sustainable yield does not provide insight into the pressure of rising groundwater on the land, biodiversity or surface waters.