Water balance results

Water balances have been compiled for a range of catchments and scales across the nation. These water balances have been assessed for the July 2004 to June 2005 financial year and are presented individually in the Regional Water Resources Assessments section.

The combined results from the water balances have been used to assess how much water Australia’s systems have; how much is stored; what the variability factors are; and what the connections between resources are.

A discussion of the relative contribution of the main components of the balances is provided. However, care should be taken to avoid taking single figures out of context, as the intent is to assess the overall balance. Some comment on the context of the data has been provided where available to ensure the data is not misrepresented.

Simplified model of water balance, showing inflows, storages and outflows

Simplified model of water balance, showing inflows, storages and outflows

Further discussion of the water balances has focussed on drawing out the key messages from a national, state and regional perspective which are summarised according to the different scales (individual, interjurisdictional or capital cities) of the water balances.

This section is split up according to the main components of the water balances:

Water balance inflows

Climate variability is generally the greatest influence on the water balance inflows. With regard to the completed water balances there is no “norm” upon which water management decisions can be based. The variability across Australia is so great that not only the water source (groundwater or surface water) varies, but the nature of the resource is also highly variable. Broadly speaking there are five different areas in which water balances have been compiled:

  • Tropical zones covering the northern extent of Australia, covering the Timor Sea and Gulf of Carpentaria Drainage Divisions (Zone 4 in Australian Rainfall and Runoff);
  • Arid interior covering much of NT, SA and WA and QLD, which includes the Lake Eyre, Bulloo-Bancannia and Western Plateau Drainage Divisions, and much of the Indian Ocean Drainage Division (Zone 5 in Australian Rainfall and Runoff),
  • Temperate zone of south west Western Australia covering the South West Coast Drainage Division (Zone 8 in Australian Rainfall and Runoff),
  • North east coast division of NSW and QLD covering the North East Coast Drainage Division (Zone 3 of Australian Rainfall and Runoff), and
  • Temperate zones (Zones 1, 2 and 6 of Australian Rainfall and Runoff) of the Murray-Darling Basin and south-eastern Australia (including Tasmania).

Similarities between balances occur within these zones as rainfall patterns and runoff behaviour is similar.

Fate of rainfall

The average proportion of rainfall in 2004-05 to average rainfall for the water balances for 2004-05 was 92%. This varied from 45% in central Northern Territory to 135% in Carnarvon groundwater management unit. The Gwydir, Namoi and Hunter Rivers regulated water management areas also had above average rainfall for the 2004-05 year.

The 2004-05 annual rainfall and the monthly average rainfall for each area are provided in the Regional Water Resources Assessments section.

Returns from the economy

Returns from the economy (i.e. water that has been delivered once to a user and then is re-used or passed on in the water cycle) in the water balances included the following items:

  • Surface water returns from the economy:
  • Urban treated effluent
  • Irrigation returns
  • Other returns
  • Surface water returns from the economy outside of entity (i.e. from an adjacent water management area)
  • Groundwater returns from economy
  • Drainage to groundwater from irrigation
  • Seepage from septic tanks
  • Seepage from Surface water features (e.g. dams, wetlands, etc)
  • Conveyance losses (seepage from channels)
  • Aquifer reinjection (e.g. ASR)

Comparing the returns from the economy to total inflows within the water balance areas, most of the areas have less than 5% returns to the economy (water used twice or passed back into the system), with a few notable exceptions:

  • Murrumbidgee Regulated (9%) – irrigation and other surface water returns
  • Pioneer (9%) – returns from outside the entity
  • Adelaide (12%) – urban treated effluent returns
  • Wimmera (15%) – irrigation returns to groundwater

Most of these areas have significant irrigation returns except for Adelaide which has a high level of recycling of urban treated effluent. The capital city water balance effluent returns are discussed in more detail elsewhere.

Surface and groundwater inflows from other entities

Surface water inflows other than runoff within the catchment generally occur from upstream tributaries which lie outside the water management area. This is especially true for those water management areas within the Murray-Darling Basin (Murray-Darling Basin), and the regulated water management areas in NSW which only cover a portion of the catchment. Depending on the boundary of the water management area it may only encapsulate part of that catchment and so it is not hydrologically independent of neighbouring water management areas.

Groundwater inflows from other catchments would be expected to be detailed in all water balances as in most water management areas the aquifer crosses the boundary. If the water management area does not include all aquifers then it will also have components from inter-aquifer leakage from other aquifers situated either above or below the aquifer detailed by the water management area. These inter-aquifer components occur within a spatial entity, however, not all water management areas include all aquifers of all depths and they may be defined for individual aquifers. This means that most water management areas would be expected to have a component of inflows from other aquifers (via vertical leakage), or from throughflow. Reviewing the data it is apparent that most of the water management areas do not have data on aquifer throughflows or from vertical leakage. Those with data on groundwater inflows are predominantly groundwater management areas or those highly dependent on groundwater for supply such as in Western Australia, South Australia and the Northern Territory.

The Murrumbidgee, Murray-Darling Basin, Carnarvon (99% of inflows) and Hobart water balances have nearly 1 million ML of surface water inflows from other entities. There are also significant inflows from groundwater from other entities for the Perth, Great Artesian Basin and Lake Eyre water balances. These areas hence have a high % of total inflows from flows from other entities and transfers.

Bolivar recycled water aquifer storage and recovery (ASR) trial site on the Adelaide Plains, South Australia. 2002
Bolivar recycled water aquifer storage and recovery (ASR) trial site on the Adelaide Plains, South Australia. 2002
Image by Bob Schuster, sourced from CSIRO Land and Water

Transfers in

The volume of water transferred in (either groundwater or surface water) to a water management area was compiled for each water balance. It is apparent from the data that the following water management areas have transfers in from other entities:

  • Sydney (124 GL)
  • Murrumbidgee (8 GL - small transfer in from the Snowy Scheme)
  • Brisbane (12 GL)
  • Adelaide (110 GL)
  • Pittwater-Coal (11 GL - transfers from Hobart supply system)
  • Melbourne (81 GL)
  • Wimmera (33 GL)
  • Perth (37 GL - including Gnangara Mound)
  • Snowy River combined water management area (486 GL)

Most of these transfers occur in the capital cities (5 of the 8), with the exception of the Snowy and Murrumbidgee water management areas where transfers occur as part of the operation of the Snowy hydro-electric scheme, and the Pittwater-Coal water management area which takes water from Hobart Water’s supply system.

Based on the water balance data the other 38 water management areas appear to be able to source enough water from within the water management area, either from groundwater or surface water sources. Whether this changes in the future will depend on the economic viability of developing such transfer systems and the level of restrictions imposed by water authorities and the impact of water trading on where people will source their water from. The capital cities will continue to rely on transfers in from neighbouring catchments, but possibly without any increase to the current level of transfers if other alternative sources such as desalinisation, effluent re-cycling, and drainage water use are taken up in each city, coupled to water demand management initiatives.

Water balance outflows

Evapotranspiration from water balances

The evapotranspiration (ET) component of the water balances includes the following terrestrial ET components:

  • Evaporation from major storages (part of surface water outflows)
  • Evaporation from minor storages, including farm dams and wetlands
  • Evapotranspiration from surface waters including rivers, channels, and other expressions of surface runoff
  • Evapotranspiration from groundwater either from springs or vegetation (not including use of soil moisture from the unsaturated zone)

Of these four components the main item that information is available for is major storages which are generally well monitored with either pan evaporation measurements or modelled estimates. Some information is available for minor storages, which may also include seepage losses to groundwater where it is representative of a total volume lost from the storage, whilst there is little information on evapotranspiration from either surface waters or groundwaters. The most information on groundwater ET losses is found in the arid interior where groundwater springs are well known and understood, or where models of the aquifers have been used to estimate the ET losses from groundwater.

Evapotranspiration accounts for nearly 90% of rainfall in Australia. The remaining 10% ends up as runoff and recharge to groundwater. It is the fate of this runoff and recharge that the water balance primarily deals with. As shown in Table 4 the evapotranspiration losses in the water balances range from 1% to more than 100% of the runoff and recharge inflows. The inconsistency in the data is due to two reasons: (1) in many cases data was not available on ET components of the water balances; and (2) the variability in ET across the water balance areas is significant.

Even when the data is viewed in terms of which drainage basin the water balance area lies in, the percentage of runoff and recharge lost to ET is not consistent. Also, in areas where extensive models and monitoring of water resources has occurred the information and data available on evapotranspiration is not consistent.

As expected though the data does show that the arid interior and northern zones of Australia have higher ET losses than seen in southern Australia. What may not have been expected is that some of the capital cities have shown high ET losses when compared to the runoff and recharge volumes. The percentage of runoff and recharge lost to ET was estimated at: 41% for Sydney; 11% for Adelaide; 12% for Hobart, and 19% for Darwin. ET losses from major dams are the main contributor to the losses in most of these cities, with 11 to 15 GL lost in Melbourne, Canberra, Adelaide and Hobart, 24 GL in Adelaide, 48 GL in Perth, 144 GL in Darwin and 175 GL in Sydney from surface waters.

Further work is required to improve the availability of data for evapotranspiration rates from groundwater and surface water. In most water balances the data sets are either derived from rainfall data; losses in models (i.e. the balancing term); from some monitored data for major storages which historically have had the best information on evaporation from open waters, or are ‘guesstimates’ or assessed as the ‘balancing item’ from a model or water balance.

For this reason further studies are required into ET to determine the true impact of it on the water cycle and on the terrestrial phase as used in the water balance.

Extractions and Diversions

Extractions and diversions are defined as the volume of water taken from a water source. Groundwater extraction volumes will include any transfer, application or storage losses in addition to the actual water consumed. Similarly, surface water diversions from rivers and storages will include any losses from the system (channels, pipes, evapotranspiration, etc) in the amounts diverted for use. This means the definition of water extracted or diverted will differ from the water use volumes that the ABS have compiled in the 2004-05 Water Account. The extractions and diversions listed for the water balances also includes “private” or self-extracted water from groundwater bores (stock and domestic, petroleum, etc) and farm dams and pumps from rivers/channels which are not always licensed, and hence may not have been included in the Water Account.

Extractions and diversions are one component of the water balance that is generally well known, especially where it is from water supply authorities and other major users. The smaller extractions and diversions from farm dams and groundwater bores are not as well known and this is apparent in the lack of data in the water balances on farm dam diversions and groundwater bore extractions.

The climate in 2004-05 is known to have resulted in less than average rainfall, but the impact of this on the demand for extractions and diversions is not known. Generally, the lower the rainfall, the higher the demand for alternative sources of water for irrigation and household garden watering. However, for licensed users this also means restrictions in that year so the actual volumes they divert or extract will be less than normal. A series of assessments is required to monitor the impact of the increased demand due to lower rainfall, and the reduced ability to extract due to restrictions. Further water balances will allow for this comparison to be made.

The main points to note with regard to the comparison of extractions and diversions against entitlement volumes are noted below. Due to extractions and diversions including self extracted sources which are not always licensed (e.g. groundwater stock and domestic bores in some areas, farms dams, flood harvesting, etc), some differences were expected. However, in general extractions and diversions (i.e. the volume of water taken from the water source) should be less than the entitlement volume (the volume licensed to be taken). There will also be some variation due to spatial differences in the way the data was compiled.

  • the ABS entitlement data may not include self extracted groundwater for town water supply or stock and domestic bores in water balance areas such as in the Northern Territory, the Great Artesian Basin, Cooper Creek and Lake Eyre where extractions exceed the entitlement volumes considerably
  • the ABS entitlement may not include surface water diversions from farm dams in many catchments in south east Australia or south-west Western Australia. A significant difference in volume has been noted which closely matches the self-extraction volumes from farm dams in parts of Victoria and Tasmania.

The comparison of extractions and diversions against the modelled water use volumes from the ABS water account are presented and discussed in Section 4.3 of the Water Availability National Perspective report available on the Publications page.

Of the 51 water management areas, there are four areas that have shown higher levels of extractions than net inflows (including transfers) from the water balances. These are the Great Artesian Basin (127%), Adelaide (118%, which includes the Patawalonga water management area at 321%) and Mereenie Sandstone (202%).

Excepting Antarctica, Australia is the driest continent in the world, which is indicated when the impact of evaporation in the water cycle is reviewed, since it takes 90% of the rainfall. Significant components of the use and demand for water are not well known. Current licensed volumes are well known in many areas, however there are still some use types that are not licensed or historically have not been licensed and hence do not appear in current license registers (e.g. flood harvesting, stock and domestic use and farm dams). Extractions and diversions are metered in some areas, and in other areas are not known at all with estimates based on licensed volumes (which may also not be well known).

Further work is required to determine the level of licensed use across each state (e.g. use of state water registers) and then the actual level of use (e.g. metering of use). Water registers and metering of water use is currently occurring in many areas and future water balances should be able to benefit from the increased availability and reliability of this data.

Stream and aquifer outflows

Water resources are integrally connected between groundwater and surface water resources within catchments and across basins. The nature of the connections has been documented within the water balances where known. From the water balances it is clear that data on groundwater / surface water interactions is limited and unreliable. Even those water management areas with information have estimated the volume interchanged between streams and groundwater generally based on the current, or “developed” condition. This means that the current exchange between groundwater and surface waters will already have been impacted by the level of development within the basin. In a “natural” system where groundwaters are not extracted and the groundwater level has not dropped, the flow to a stream, especially in low flow conditions, would be considerably higher than what we currently experience. In other cases due to regulation of the rivers and higher flows than would naturally occur, the groundwater levels may be higher near the rivers than under natural conditions. This means that individual reaches need to be assessed across each catchment as the variability of the level of connection and impact of development of groundwater and surface water resources can differ markedly throughout the catchment.

Groundwater and surface water interaction has been documented in two ways: as a net exchange between the two systems, and as an absolute total of the transferred volumes between groundwater and surface water. There is no standard methodology of determining stream and aquifer interaction flows for a catchment or water entity. Traditionally they are assessed as a rate of flow exchanged between surface water and groundwater for a given reach. When the reaches are added for a larger area, such as for the water balances, this means that some of the exchanges may cancel each other out when summing the terms (e.g. the net volume is less than the total exchange).

A comparison of the groundwater/ surface water interaction volumes was made against recharge and runoff to show the proportion of the fate of rainfall in the balances that occurs as an exchange between surface water and groundwater. Further work is required to understand the level of interaction and the areas where either surface water diversions or groundwater extractions may impact on this relationship and hence impact on environmental flows or associated ecosystems.

Ten of the water management areas have greater than 20% of the runoff and recharge volume interchanged between groundwater and surface water, with another 9 areas with more than 10% interaction. This means that 20% of the water balance areas have significant known groundwater-surface water interactions. Many others have no information, which implies that the potential for double counting of the water resource is very high in many catchments. These values are indicative only as this assessment is dependent on the runoff and recharge figures used and in some cases the reliability of these is less than ±25% which can have a significant impact on the resulting connectivity category. It should also be noted that it is a generalised estimate of the level of connectivity across the catchment which will vary by reach.

Comparison of total runoff and recharge with total groundwater / surface water exchange volumes for the water balance areas

Comparison of total runoff and recharge with total groundwater / surface water exchange volumes for the water balance areas

Outflows to other entities

Outflows to other entities are flows that naturally occur, such as streamflows and aquifer flows. The outflows to other entities are principally flows to coastal or estuarine areas, downstream catchments, or to other aquifers outside the boundary of the water management area. The surface water outflows are generally well known where gauges exist. The groundwater outflows are generally only known where groundwater models of the system have been constructed, such as in Perth or the Great Artesian Basin, or where a specific study on part of the water management area may have been undertaken such as in the Burnett and Barron water management areas in Queensland.

Transfers out

Transfers out differ from outflows to other entities as they are not naturally occurring flows, they are facilitated by infrastructure via channels, pipes, or other mechanised means. There are 11 water balance areas that have transfers out of the entity to another entity. Most of these transfers correspond to urbanised areas near the capital cities where a transfer from the capital city water supply system may occur, or they are transferring water to that capital city. There are two exceptions to this: (1) in Victoria where transfers from major dams in western Victoria (Glenelg water management area) occur for irrigation purposes; and (2) from the Murrumbidgee water management area to the Snowy hydro-electric scheme. In most other areas, water is sourced and used within the water management area.

Water balance storage volumes (opening and closing)

Within the water balances, the major opening and closing volumes are for major surface water storages only. The minor volumes include farm dams, small catchment dams, and some other additional storage types. One of the discrepancies found in undertaking the water balances was that there is no accepted definition for small farm dam or catchment dams across Australia.

Each state defines them differently and hence licences them differently. This means that the quality of information varies across jurisdictions and in some states across regions where the licensing is regionalised. Farm dams are one of the three major water interception activities which the NWI nominates as having significant impact on catchment runoff and resource sustainability. Further work is required to define farm dams consistently across the country, and to adopt consistent licensing practices so that any water accounts can portray an accurate, detailed and consistent picture of the use and extent of farm dams in each water management area.

Groundwater storage volumes are not shown as they have only been calculated for the NSW areas, and in some other areas used as the balancing item instead of reporting an error term. The reporting of groundwater storage volumes is not normal practice due to the vast aquifer resources (or water stock) that may then be quantified without reference to sustainable use of the resource. This often conveys a misleading picture. The volumes requested for the water balances were in reference to management or trigger levels within the water management area. However, because there were no reported management or trigger levels for many of the groundwater resources this basis of reporting groundwater volumes available for extraction has to be questioned. In the case of aquifers being consciously “mined”, the approach is valid; however even here there was limited information available to define the actual storage volume at the start and end of the water balance period.

Of the water balances completed, 18 showed a decrease in surface water stored in 2004-05, 13 showed an increase in storage volumes, 14 had no surface water storages, and 4 had no change in storage because the storage estimates were based on storage capacity and not actual measured storage volumes at the start and end of the year.

Total capacity of major surface water storages in 1996/97 was estimated at 83,800GL which includes all major storages listed by ANCOLD (see section on Water storage in 2004-05 for further information). This storage capacity accounts for 32% of the total recharge and rainfall (Water 2010, BRS).

Thirteen (13) out of the 51 water balances do not have any major or minor surface water storages within the water management area. These water management areas are either situated in the arid zone areas of the NT and SA, or are groundwater management areas for which a water balance was undertaken (e.g. Great Artesian Basin, Ti-tree, Mereenie Sandstone). Of the remaining 37 areas that have storages, the percentage of total recharge and runoff stored on average is 42%, ranging from 2% to 194%. Those areas that at July 2004 held more than 50% of the total recharge and runoff occurring within that water management area are listed below with their percentages. Information was not obtained in the course of this work from which we can determine whether these storages are designed to withstand drought conditions and hold long term storage volumes, or whether they also take in transfers from other catchments and areas. Obviously, the larger the storage volume, the greater capacity the area has to withstand droughts or manage floods.

Generally information on major storages is well known, it is the smaller components of the water balance that are not as well known. In the short to medium term it is unlikely that major storages will increase significantly in Australia as current water policy in many states would not advocate for new storages. Alternative sources such as desalinisation plants (recently commissioned in Perth, and proposed for Sydney and Brisbane), along with effluent recycling and aquifer storage and recovery (ASR) are being reviewed to ascertain where water savings can be made, and hence where alternative water sources can be found.

Total recharge and runoff and surface water stored for water management areas with greater than 50% of total rainfall and recharge.

Water Management Area Total Recharge and Runoff (ML)
(2004-05)
Total Surface Water Stored (ML)
(July 2004)
Total Water Stored / Total Recharge and Runoff (%)
Australian Capital Territory Water Supply Area 178,000 100,677 57%
Murray-Darling Basin 20,264,450 5,735,100 56%
Brisbane Water Supply Area 1,613,000 1,147,320 71%
Adelaide Water Supply Area 214,790 153,340 71%
Sydney Water Supply Area 1,440,520 1,122,300 78%
Macquarie River - Regulated WMA (NSW) 388,000 310,300 80%
Macquarie WMA (Tas) 122,210 112,890 92%
Ord Combined WMA 8,679,280 10,806,230 125%
Hunter WMA 444,000 630,000 142%
Snowy Combined WMA 1,361,840 2645,000 194%

A more detail discussion and table of results is provided in Section 4.4 of the Water Availability National Perspective report available on the Publications page.

Unknown inflows and outflows

The water balances are based on readily available information from various and disparate data sets. This means that when the information is compiled in the water balances there will be an ‘unknown’ component to the balance. There are two ways to deal with this: (1) to allocate this volume to a term in the water balance where it is thought that the volume goes (e.g. losses, evapotranspiration), or (2) to leave it as an unallocated volume either in the inflows or outflows. The preferred approach for AWR 2005 was the second option, as it was considered more transparent.

The water balance error is based on the unknown inflows and outflows divided by the rainfall and runoff inflows. This gives an indication of the level of reliability of the overall balance as if the error is 90% then this means 90% of the inflows have not been able to be allocated to parts of the water cycle.

A more detail discussion and table of results is provided in Section 4.5 of the Water Availability National Perspective report available on the Publications page.

Summary of water balance results

The water balance results are summarised in the Table below. The table lists the six main components of the water balances:

  • Opening storage volumes (predominantly surface water dams and reservoirs with some groundwater aquifer storage volumes)
  • Closing storage volumes
  • Surface water inflows (runoff, flood harvesting, baseflow, drainage and effluent returns, etc)
  • Groundwater inflows (recharge, drainage returns, seepage, groundwater–surface water interactions, returns, etc)
  • Surface water outflows (diversions, drainage, effluent discharges, evaporation, flows out of entity, etc)
  • Groundwater outflows (extractions, evaporation, discharge to streams, aquifer flows out of entity, etc)

Summary results of the 2004-05 water balance for the 51 priority geographic areas

WMA Name

Opening storage volume

Closing storage volume

Surface water inflows

Groundwater inflows

Surface water outflows

Groundwater outflows

All volumes shown in GL
New South Wales

Gwydir Regulated

5,490

5,569

1,217

73

1,142

68

Richmond

2,920

3,017

317

167

315

73

Namoi Regulated

20,490

20,419

1,011

173

1,080

176

Macquarie Regulated

9,239

9,243

376

110

377

105

Hunter Regulated

1,568

1,555

411

110

483

51

Lachlan Regulated

76,830

76,784

228

193

258

210

Murrumbidgee Regulated

119,534

119,800

2,548

558

2,466

373

Northern Territory

Daly River

0

0

7,101

4,842

7,101

4,842

Goyder River

0

0

1,700

287

1,700

287

Roper River

0

0

5,551

1,731

5,551

1,731

Ti Tree

2,140

2,140

6

10

6

10

Mereenie Sandstone

4,810

4,802

0

4

0

12

Queensland

Burnett

639

449

2,112

147

2,301

147

Pioneer

87

88

529

57

528

57

Condamine-Balonne

103

80

691

1,075

715

1,075

Barron

385

328

1,235

87

1,292

87

Georgina-Diamantina

0

0

500

1,025

500

1,025

South Australia

Rocky River

0

0

14

10

14

10

Barossa

0

0

17

10

17

10

Patawalonga

0

0

86

22

86

22

Limestone Coast

0

0

414

1,326

414

1,326

Tasmania

Macquarie

113

113

222

19

222

19

South Esk

28

28

325

33

325

33

Mersey

159

28

951

33

1,082

33

Pittwater-Coal

22

20

66

8

68

8

Victoria

Goulburn River

901

1,102

2,464

235

2,263

235

Broken River

111

123

251

59

239

59

Ovens River

25

28

1,512

137

1,510

137

Wimmera River

66

48

215

463

233

463

Glenelg River

53

23

178

113

209

113

Moorabool River

16

27

104

25

93

25

Western Australia

Harvey River

26

36

538

66

528

66

Collie River

125

167

323

65

281

65

Carnarvon GWA

0

0

1,938

19

1,938

19

Gnangara Mound

0

1

657

686

657

686

South West Yarragadee

1,200,067

1,200,067

862

633

862

633

Capital cities

Australian Capital Territory water supply area

101

99

243

29

245

29

Sydney water supply area

135,946

135,707

978

1,053

1,217

1,053

Darwin water supply area

250

180

739

130

793

146

Brisbane water supply area

1,147

803

1,475

244

1,819

244

Adelaide water supply area

153

169

369

155

353

155

Hobart water supply area

14

13

4,646

11

4,647

11

Melbourne water supply area

238

254

1,889

162

1,874

162

Perth water supply area

174

189

888

850

874

849

Interjurisdictional areas

Murray-Darling Basin

5,735

6,566

16,135

5,967

15,304

5,967

Snowy River

8,085

8,012

2,250

247

2,323

247

Cooper Creek

0

0

190

1,144

190

1,144

Ord River

10,806

9,598

8,675

499

9,886

496

Lake Eyre Basin

0

0

600

3,973

600

3,973

Great Artesian Basin

0

-266

0

430

0

696

Border Rivers

4,818

4,804

395

46

408

46

Summarising the water balance information presented above, the main points to note are as follows:

  • Rainfall in 2004-05 was below average for most of the areas for which water balances were completed, except in northern NSW (Gwydir, Namoi, Hunter Regulated water management areas)
  • Surface water inflows from other entities were significant in the Murrumbidgee, Murray-Darling Basin, Carnarvon and Hobart
  • Groundwater inflows from other entities were significant in Perth, the Great Artesian Basin, Lake Eyre and Mereenie Sandstone water management areas
  • 5 of the 8 capital cities had significant transfers in, with only three other water balance areas listing transfers in (Snowy and Murrumbidgee water management area for the Snowy hydro-electric scheme) and the Pittwater-Coal water management area which takes water from Hobart Water’s supply scheme.
  • 38 of the water balance areas did not require transfers in to meet demand for water within the water management area.
  • Evapotranspiration from the water balances shows a lack of consistent and reliable data on ET from groundwater and surface water. This not only occurs in those areas which are data deficient, but also areas which have been extensively monitored such as the Murray-Darling Basin.
  • The climate in 2004-05 is known to have resulted in less than average rainfall, but the impact of this on the demand for extractions and diversions cannot be ascertained from the water balances. Generally, the lower the rainfall, the higher the demand for alternative sources of water for irrigation and household garden watering. However, for licensed users this also means that there will be restrictions in that year so the actual volumes they divert or extract will be less than normal.
  • Current entitlement data does not appear to include self extracted groundwater and surface waters such as farm dams. When comparisons of this data with extractions and diversions is undertaken, this can lead to extractions being greater than the entitlement volumes and the appearance of over-use within an area.
  • Groundwater / surface water interactions need to be assessed to determine the impact of extractions and diversions from these sources on the other resource. Further work is required to understand the significance of these transfers in each of the catchments.
  • There are 11 water balance areas that have transfers out. Nine of these occur from water management areas to capital cities. The other 2 occur from the Murrumbidgee to the Snowy hydro-electric scheme, and from the Glenelg to Wimmera for irrigation purposes.
  • Eighteen areas showed a decrease in surface water stored in 2004-05 with another 13 showing an increase in storage. Generally the decreases experienced were greater than the increases in storage, and most capital cities had either a significant decrease or only a nominal change in storage for 2004-05.
  • Generally major storages are well known. Minor storages such as farm dams are not well known and need further work to understand the impact on the streams and catchments.
  • Groundwater resources are not well known in most areas with areas with extensive investigations not understood in terms of sustainability and use of the resource. Further work is required to understand the use and sustainability of groundwater resources.
  • Many of the water balances have indicated that there are no unaccounted for flows (i.e. the change in inflows and outflows is equal to the change in storage). In many of these water balances an assessment of where the difference should go has been made (e.g., losses occur as ET) which does not mean the data is higher reliability than in those which do have unaccounted for flows.

Further discussion of the water balance results is provided in the Water Availability National Perspective report, and the Regional Water Balances report, which are both available on the Publications page.

For individual results of water balance assessments go to Regional Water Resources Assessments

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Last Updated 29/06/2007