Water Use

Introduction

As the Surface Water Resources page indicates, Australia's climate and, in turn, its surface runoff and streamflow are characterised by large variability from one year to another. The variability of precipitation also results in variations in the use of water from year to year, particularly for irrigation. In a sense, no year can be regarded as 'normal'. However, the last occasion on which a national survey of water use was undertaken, 1983-84, was a particularly 'abnormal' year. This was especially true over most of the Murray-Darling Basin, where drought conditions in the early part of the year, with consequent restrictions on water use, were followed by very wet conditions, both factors resulting in reduced water use for irrigation. The 'abnormal' conditions of 1983-84 become very evident when comparisons are made with the previous survey of water use in Australia undertaken in 1977 (Table 1). The lower consumption of water for irrigation accounts for virtually all of the difference between the two surveys.

Data on water use by the major use categories for Australia's Drainage Divisions are given in Table 2 (AWRC 1987, Volume 2) (see Surface Water Resources). Of particular interest are the figures for water use as a percentage of divertible resources. It should be noted that the figures only cover the actual measured and/or estimated consumptive or off-stream uses of water.* No data are available for non-consumptive or instream uses, such as hydro-electricity generation, fishing, recreation or water required for aquatic and environmental purposes, that is, the health of the river environments.

* : No data are available for unmeasured use from such sources as rain water tanks, farm dams, etc.

Water use within the Murray-Darling Basin

Of Australia's total estimated water use in 1983-84, 59.3 per cent occurred within the MDB (Table 2). For the MDB as a whole, water use was and is dominated by irrigation. Indeed, irrigation in the Basin accounts for 52.4 per cent of all water used in Australia, and 75.0 per cent of all irrigation water is used in the MDB (Table 3). There are significant variations in gross water use between individual river basins within the MDB, as indicated in Table 4.

Though it is only a small percentage of the total, the MDB has the fourth highest figure for 'Urban and Industrial' water use (Table 2). This is a reflection of the fact that the Basin accounts for most of inland Australia's urban and economic activity. The Basin has by far the highest figure for 'Rural' water use (domestic use on farms and livestock).

More recent data were compiled as part of the audit of water use in the Murray-Darling Basin (Table 5) (MDBMC 1995, 6-7), with up-dates available in the annual reports of the audit monitoring process (see The Cap). Between 1988-89 and 1992-93, the total average annual diversion of water from the Basin's waterways was 10,684 GL, 95 per cent of which was diverted for irrigation.

In all water supply or distribution systems there are transmission losses due to various causes, such as leaking pipes, evaporation, and seepage to groundwater from canals. In other words, not all water reaches its intended place of consumption. However, such water is included in the data for gross water consumption. For the Basin as a whole, transmission losses are estimated to be over 14 per cent of gross water consumption. The figures vary considerably from one river basin to another, largely as a consequence of the type of water distribution system. The biggest losses occur from open and unlined water supply channels due to evaporation and seepage, as for example in some irrigation areas and the Wimmera-Mallee domestic and stock water supply scheme. Such open channels are gradually being replaced by pipelines, as a result of which reticulation losses have been reduced dramatically. The elimination of associated losses due to evaporation is also resulting in improved water quality. In the Sunraysia area, the replacement of open channels by pipelines has virtually eliminated evaporation and seepage losses resulting in a saving of 2,700 ML per annum, water that has been made available for beneficial uses (Anon. 1995).

Inter-basin transfers: movement of water into and out of the MDB

There are a number of water supply schemes that involve the movement of water into and out of the Murray-Darling Basin (Table 6). By far the most important of the inter-basin transfers are the diversion of the headwaters of the Snowy River into the Basin and the pipelines that take water out of the Basin in South Australia. The Snowy River diversion forms part of the Snowy Mountains scheme and the increased quantities of water in the Murray and Murrumbidgee Rivers make an important contribution to the availability of water for hydro-electric power generation and irrigation. Because of the scheme, the average annual flow of the Murray at Albury is 10 per cent higher than under natural conditions, but this can rise to around 33 per cent in dry periods (MDBMC 1995, 14; MDBC 1990).

Water from the River Murray plays a critical role in the life and economy of much of South Australia. On average, 52 per cent of all water used in the State comes from the Murray. It is the main source of water for Adelaide, supplied by the Mannum-Adelaide (67 km) and Murray Bridge-Onkaparinga (48 km) pipelines (Figure 2). On average, metropolitan Adelaide receives some 42 per cent of its water from the Murray and up to 90 per cent in drought years (MDBMC 1995, 26). Two pipelines take water from Morgan to the northern Spencer Gulf ‘Iron Triangle’ industrial towns of Port Pirie, Port August and Whyalla (359 km), with a line further north to Woomera. With some 90 per cent of their water coming from the Murray, these towns and their industries would not exist without the pipelines (see Manufacturing Industry). Two other pipelines serve large rural areas of the state, Swan Reach-Stockwell (53 km) and Tailem Bend- Keith (143 km).

Water Storages

There is a long history of construction of regulatory and storage structures in the Murray-Darling Basin, the response to the naturally high level of variability of precipitation and stream flows. Some structures occupy key places in Australia's history, such as the Hume Reservoir (Anon. nd) and Yarrawonga Weir (Loughnan 1989). The Murray-Darling is now a highly regulated river system, with numerous dams, reservoirs, weirs, locks and barrages on all of the major and many of the minor rivers. Without the extensive regulation, the storage structures and their associated reticulation systems, the size and nature of water use outlined above would not be possible and the Murray-Darling Basin and especially much of South Australia as we know it today would not exist.

Table 7 lists the main storages with capacities of 10,000 ML capacity and over. There are 84 such storages, 40 in New South Wales, 27 in Victoria, 7 in Queensland, 7 in South Australia, and 3 in the ACT. Their total storage capacity is 34,727,200; over 94 per cent of the total is in the 30 storages with capacities of 100,000 ML or more (Figure 1 and 3)**. Storage volumes on the Murray, Goulburn, Murrumbidgee and Gwydir Rivers are significantly greater than the average annual flows from their catchments. Of these, the Gwydir is also a particularly variable river so that if its storages are emptied, they can take many years to fill. For most rivers, water use is not much less than the regulated flow.

Farm dams have long provided important sources of water for livestock and other purposes. The total numbers of dams and quantities of water involved are considerable. However, the large on-farm storages that have been constructed in increasing numbers over recent years are of a different order of magnitude, especially those associated with cotton growing in the northern part of the Basin. They are not included in the above data. It is estimated that the total volume of such on-farm storages is over 1.2 million ML (MDBC 1994, 53; see also Wettin et al. 1994). In some cases, the water used to fill these dams is taken from "off-allocation water", when there are flows that are surplus to river requirements, such as during floods. In other cases, they fill from local runoff.

** : Two of the storages, Eucumbene and Jindabyne, are just outside the Basin but are included as they are major storages of the Snowy Mountains scheme and so directly linked to the Basin.

Groundwater use

In 1983-84, groundwater accounted for 7.36 per cent of gross water consumption in the Murray-Darling Basin (see Groundwater Resources). As Table 4 indicates, its use varies significantly from one part of the Basin to another, both in actual quantities and as a percentage of total water use. In many locations, it is the major source of water, often the only source, especially in the arid and semi-arid northern and western parts of the Basin, for domestic and livestock use on the large pastoral properties, for mining activities, and for numerous towns. In a number of areas, groundwater is also important for irrigation.

In the early 1980s, it was estimated that there were about 50,000 groundwater bores in the Murray-Darling Basin (Jacobson et al. 1983, 13). Close to half of them drew water from the Great Artesian Basin.

Two particular aspects of the use of groundwater merit brief consideration. Firstly, there is a low rate of recharge of the aquifers and much of the groundwater being used is fossil water that is not being replaced. This is of particular concern where the water is used for irrigation. For example, the volume of water stored in the alluvial or surficial sediments in the lower Namoi Valley is estimated at about 20,000 GL, but the average annual natural recharge is only about 30 GL (MDBMC 1987, 81). Many aquifers are already subject to a high rate of use, with abstractions close to two-thirds of average annual recharge. In a number of locations, the use of groundwater is in excess of the recharge rate, which means that the resource is being 'mined'. Important examples have been the Condamine Valley, the Namoi Valley, and the Angas-Bremer area (on the western shore of Lake Alexandrina). In the latter case, excessive use has caused the intrusion of water from saline aquifers.

Over recent years, however, much more attention has been given to the management of groundwater resources. There is an increasing level of control on extractions, particularly as far as irrigation is concerned, to ensure supplies for urban, domestic and stock uses are not put at risk. Where both surface and groundwater are available, they are being regarded as one resource under conjunctive use management systems, as in the Gwydir Valley. In the Condamine catchment, strict controls have been placed on the use of groundwater, including reductions in allocations and the establishment of surface water substitution schemes (Stallman 1995).

The second point to note is the flow of groundwater from free-flowing bores, especially in the Great Artesian Basin. This a major waste of water and there is frequently associated land and vegetation degradation in the immediate vicinity of free-flowing bores caused by both domestic livestock and native animals using the uncontrolled watering points. With the aid of a joint Federal-State-landholder program, these bores are being brought under control through their capping and the use of plastic pipelines for water distribution (Lyon 1995). One of the best illustrations is north of Moree, where a group of twenty-two graziers and wheat farmers capped the Milroy Bore and converted 76 km of open channels to pipelines to take water to their properties. The pipelines are made of a special plastic that can cope with the 51°C temperature of the water when it comes out of the ground. The change has increased the efficiency of water use from 4 to 94 per cent and the farmers are earning at least a 30 per cent return on their investment.

Conclusion

The Basin's water consumption continues to grow (Figure 4). From 1988 to 1994, consumption increased by 7.9 per cent overall (MDBMC 1995, 9). In the northern parts of the Basin, the percentage increases were very much greater, very largely as a result of the expansion of the cotton industry, though large increases, in real terms, were also experienced in other areas (Table 8).

However, though water consumption is increasing, it is still well below the level of entitlements, that is, the quantities of water licence holders are entitled to take under the varying conditions that prevail from from year to year (MDBMC 1995, 6-8, 37). Table 9 shows that the total average annual diversions for the period 1988-89 to 1992-93 were only 63 per cent of diversions permitted under the allocation systems.

Water use is increasing by about one per cent a year (MDBMC 1995, 10-13). The fact that only about two-thirds of entitlements are being used means that there is considerable scope for further increases in consumption, without any change in entitlements, by as much as 14.5 per cent per annum. Picking up a point from the water audit (MDBMC 1995, 3), one of the Murray-Darling Basin's former Commissioners stated that the existing system of water allocations acts to restrain water use during periods of drought. The study showed that under normal non-drought conditions the system was not effective in controlling water use. This was not really surprising, because that system evolved at a time when water managers had the task of encouraging development that would make use of the cheap water that was available. It was a system designed to promote distribution - not restrain consumption (Toyne 1995).

However, as the water audit (MDBMC 1995, 35-36) and many of the pages on this site clearly indicate, continued growth in diversions is not sustainable. Such growth of water consumption would have disastrous consequences for the Murray-Darling river system and the Basin as a whole, leaving even less water for essential in-stream requirements. A healthy river system would be impossible to achieve. It was for these reasons that the Murray-Darling Basin Ministerial Council made a number of critically important decisions at its June 1995 meeting:

• a balance must be struck between consumptive and instream uses of water in the rivers of the Murray-Darling Basin;
• diversions must be capped;
• an interim moratorium would be introduced immediately on further increases in diversions while the precise details of the long-term cap are established; and
• the community would be advised of the outcomes of the Water Audit report (Blackmore 1995) (see The Cap).

The moratorium was extended to June 1997 to allow an Independent Audit Group time for further studies and an examination of the Cap, and especially the equity issues that are involved, by an Independent Audit Group (IAG). The IAG gave overall support to the continuation of the Cap (MDBMC 1996). Reaching agreement on the balance between consumptive and instream uses and the level of the cap on diversions, for the Basin as a whole and its various parts, is the most important issue the Ministerial Council has had to face.

References

ANCOLD (1990): Register of Large Dams in Australia April 1990. Australian National Committee on Large Dams, c/o Hydro-Electric Commission, Hobart.

Anon, (nd): Hume Reservoir. River Murray Commission, Canberra.

Anon. (1995): "$1 million for Murray water". Water Resource Management News, 2(5), 11.

AWRC (1987): 1985 Review of Australia's Water Resources and Water Use. Australian Water Resources Council. Department of Primary Industries and Energy/Australian Government Publishing Service, Canberra.

Blackmore, D. (1995): "The water audit". In Proceedings of the Water Use and Environmental Flows Workshop, 22-23 August 1995. Murray-Darling Basin Commission, Canberra.

Jacobson, G. et al. (1983): Australia's Groundwater Resources. Water 2000: consultants report No.2. Australian Government Publishing Service, Canberra.

Loughnan, A.N. (Editor)(1989): Harnessed Water - a River Dammed: the construction of the Yarrawonga Weir and formation of Lake Mulwala. Yarrawonga Shire Council, Yarrawonga.

Lyon, N. (1995): "Great Artesian Basin bores rehabilitated". Australian Farm Journal, 5(8), 66-67.

MDBC (1990): The River Murray System: the regulation and distribution of River Murray waters. Murray-Darling Basin Commission, Canberra.

MDBC (1994): Murray-Darling Basin Commission Annual Report 1993-94. Murray-Darling Basin Commission, Canberra.

MDBMC (1987): Murray-Darling Basin Environmental Resources Study. Murray-Darling Basin Ministerial Council, Canberra.

MDBMC (1995): An Audit of Water Use in the Murray-Darling Basin. Murray-Darling Basin Ministerial Council, Canberra.

MDBMC (1996): Setting the Cap: report of the Independent Audit Group. Murray-Darling Basin Ministerial Council, Canberra.

Stallman, K. (1995): "The Condamine catchment comes to grips with water use". Curlew, 11, 2.

Toyne, P. (1995): "Water use and environmental flows in the Murray-Darling Basin". In Proceedings of the Water Use and Environmental Flows Workshop, 22-23 August 1995. Murray-Darling Basin Commission, Canberra.

Wettin, P. et al. (1994): "Water sharing and floodplain wetlands in the Murray-Darling Basin". pp. 24-41 in Murray-Darling Basin Floodplain Wetlands Management: proceedings of the Floodplain Wetlands Management Workshop, Albury NSW, 20-22 October 1992. Murray-Darling Basin Commission, Canberra.

Figure 1 Water storages in the MDB

Figure 2 Water pipelines and areas served by them in South Australia

Figure 3 Growth in Murray-Darling Basin storages since 1920 (source: MDBC 1994, 51)

Figure 4 Growth in water use in Murray-Darling Basin since 1920 (source: MDBC 1995, 13)

Table 1 Water use in Australia, 1977 and 1983-84 (source: AWRC 1987, Volume 2)

Table 2 Water use by Drainage Divisions, 1983-84 (source: AWRC 1987, Volume 2)

 Table 3 Water Use in the MDB, 1983-84 (source: AWRC 1987, Volume 2)

Table 4 Gross water consumption, by river basins, 1983-84, in GL (source: AWRC 1987, Volume 2)

Table 5 Surface water use in the Murray-Darling Basin: average actual diversions, 1988-89 to 1992-93 (source: MDBMC 1995, 7)

* Excludes water harvesting diversions

Key Points to Note from this Table:

• Annual diversion averaged 10,676 GL/year
• Over 95% of diversions were for irrigation

Table 6 Inter-Basin Transfers of water involving the Murray-Darling Basin (source: AWRC 1987, Volume 1, 30-32)

* 130GL would be a more accurate figure.

 Table 7 Major dams and reservoirs in the Murray-Darling Basin: defined as reservoirs with a gross capacity of 10,000 megalitres or more (source: ANCOLD 1990; various MDBC and other sources)

* f - flood control; h - hydro-electricity; i - irrigation; m - industrial and/or mining; r - recreation; u - urban supplies; f - flood mitigation; n - navigation.

** Though strictly speaking outside the MDB, the Eucumbene and Jindabyne storages have been included as they are the major reservoirs for the Snowy Mountains Scheme.

Table 8 Growth in diversions of water in the Murray-Darling Basin, 1988 to 1994* (source: MDBMC 1995, 9)

* The figures are the average diversion figures from the modelled 1988 and 1994 development scenarios.

Table 9 Limits to diversions of water in the Murray-Darling Basin imposed by the allocation system (source: MDBMC 1995, 8)

* Note: For regulated streams, the diversion limit has been calculated by adding the actual diversion to the difference between the announced allocation and the on-allocation use.  For unregulated streams, the diversion limit is the licensed area converted to a volume of water.

Figures are the average actual figures for 1988-89 to 1992-93