Inland waters: Water availability and use
Independent report to the Australian Government Minister for the Environment and Heritage
Beeton RJS (Bob), Buckley Kristal I, Jones Gary J, Morgan Denise, Reichelt Russell E, Trewin Dennis
(2006 Australian State of the Environment Committee), 2006
Australia’s rainfall and river flow have always been naturally variable and could become more variable, especially in southern Australia, as a result of changes in climate and seasonal river flows (Thresher et al 2004). While the recent drought has reduced water supplies across much of the country, in some regions the decline appears to have occurred during the past three decades. The situation in Western Australia is particularly severe, with Perth water supply catchments yielding 50 per cent less water than in the years before the mid-1970s, as a result of changes to rainfall as well as revegetation of the catchment. The extent to which this signifies a longer-term drying trend for Australia is uncertain, but the run of dry years experienced in the early 1900s could occur again, but this time for a longer period as a result of climate change. Australia should heed the warning signs, especially in view of climate change forecasts.
Apart from Darwin, all major Australian cities have been on water restrictions during recent years, with many now permanently on at least the minimum level of restrictions as water storages have emptied (Figure 28). Some larger rural cities have even had to enact emergency plans to provide essential water supplies. There are very few cities in Australia where planners are not considering strategies for dealing with issues of long-term water availability. Already there have been enormous changes, for example, in the public acceptance of the need for reduced water use in city and rural regions. The days of lush, green lawns in every Australian backyard may well be gone forever.
Source: adapted from Hanna (2003; Table 1: 398)
Regardless, demand for water is increasing across the nation, and in spite of trends to more efficient and careful water use, the pressure to build new dams and to exploit additional groundwater and river systems (especially in northern Australia) is growing. Australia is now the third largest per capita user of water in the world (Radcliffe 2004). In 2004, the Australian Bureau of Statistics published the Australia Water Account for 2000–01, which was effectively a census of Australian water use and the first since 1996–97. It showed that irrigated agriculture is the main user of water, accounting for 67 per cent of water used in 2000–01. This is a slight decrease from the level of use by that sector in 1996–97. Urban and industrial consumption accounts for only 9 per cent of water use, which is a slight increase since 1996–97 (Table 14).
|Sector||Australia’s annual water consumption (GL)|
|Irrigated agriculture||15 503||70||16 660||67|
|Forestry and fishing||19||23|
|Electricity and gas supply||1308||6||1688||7|
|Water supply, sewerage, drainage||1707||8||1794||7|
|Total||22 187||24 909|
Note: GL – gigalitre.
* Water consumption definition as in the Water Accounts
Source: Adapted from ABS (2000, 2004f)
Overall, total consumption of water has increased by more than 10 per cent in the five-year period from 1996 to 2001. If this trend continues, the gap between supply and demand will have to be addressed. Australia’s water use efficiency and water reuse and recycling rates will need to increase from the current low levels to at least those of other developed countries (Radcliffe 2004). This is not just a technical issue because public perceptions are very important for reuse to succeed, as seen in the debate around water reuse in Sydney and the current experience of some country towns such as Toowoomba (see ‘Water Futures Project—Toowoomba’. Other, more expensive solutions include building new dams or desalination plants, or using aquifer storage and recovery methods. All are controversial.
With the increasing pressure to reuse wastewater, water quality is likely to become a greater issue, as recycled water ‘fit for purpose’ will be required for many agricultural, industrial and domestic purposes. While water of poorer quality may be used for many industrial purposes (such as cooling water), other uses (such as drinking water) require high-quality water. A recent debate has focused on the technique of ‘indirect potable supply’. Under this scheme, highly treated sewage effluent would be added back into dams, where it would be further treated naturally before returning to the drinking water treatment plant for reticulation to household consumers. This has inadvertently been the practice for decades in some river systems. It is a proposal being considered by the cities of Toowoomba and Goulburn, and increasingly will be on the agenda for discussion by the rest of Australia. The environmental aspects of this technique will have to be closely considered as well as the human issues. The risk of toxic algal blooms may be increased if the recycled water is not first treated to remove the majority of the nitrogen and phosphorus that it contains.
Widespread reforestation, either through plantation forestry or through smaller scale agroforestry activities, will change the hydrology of catchments to further reduce water availability. A contentious issue is that young, rapidly-growing trees and shrubs use much more water than mature ‘bush’, leaving less to flow into rivers, lakes and dams (Zhang et al 1999, Best et al 2003, Dovers 2006).
Groundwater use is becoming the greatest challenge to sustainable water use in Australia (Table 15). There are now large areas of Australia, both urban and rural , where groundwater is being used above a sustainable level, although limited data mean that it is difficult to accurately monitor groundwater use and calculate sustainable yields . Many irrigators in the Murray–Darling Basin have switched from using surface water to groundwater since the surface water cap was introduced in 1995 (MDBC 2003). In combination with other groundwater uses, and the drought, this increase has caused groundwater levels to decline over large areas of the Murray–Darling Basin over the last decade (MDBC 2004).
|State or territory||Annual groundwater use (GL)||Percent change between 1983–84 and 1996–97|
|New South Wales||318||1008||217|
Note: GL – gigalitre
Source: NLWRA (2001b)
There are, however, positive signs in some regions. In response to declining pressures and water levels in the Great Artesian Basin, for example, many bores have been capped (Figure 29), drainage canals have been piped, and some spring wetlands restored.
Note: GABSI - Great Artesian Basin Sustainability Initiative; GAB - Great Artesian Basin
Source: Adapted from Hassall and Associates Pty Ltd (2003)