Water for Rivers

Discussion

Water is being diverted from Australian river systems for economic uses, especially irrigation. This is putting strain on ecosystems dependent on river water, including many wetlands.

Readings

The Murray River

Earthbeat, 12 June 2004

There is now widespread agreement that something needs to be done to save the Murray River in South Australia. We hear a range of views on this issue from stakeholders on the river.

Going with the Flow (A National Rivers and Water Plan)

ACF, October 2000

Most river systems across southern and eastern Australia are seriously degraded. Their persity and abundance of native fish, invertebrates (crustacea, insects, molluscs) and waterbirds are in serious decline. Wetlands, flood plains, billabongs, and aquatic and riparian vegetation are similarly affected. Riverine and wetland habitats are seriously degraded, and water quality is increasingly affected by pollution from agricultural and other sources, and in many cases from the effects of rapidly increasing salinity problems on the land.

Water was allocated to irrigators without regard for either environmental constraints or economic good sense, hence the water resources of the Murray-Darling are seriously over-allocated. When ACF surveyed freshwater ecologists in 1995, an overwhelming majority identified the need for ‘environmental flows’ as the top environmental priority for the Murray-Darling.

Weirs prevent fish migration, and this, combined with the lack of flooding, has devastated fish breeding. In many river reaches, cold water released from deep in the dams has wiped out most native fish species. Bank erosion, the draining of wetlands, the decline of riverine vegetation and snag removal has devastated fish habitat. Many rivers have silted up due to clearance of highly erodable soil types. And some have experienced high pollution loads, ranging from nutrients from agricultural, industrial and urban sources, salt from rising salinity levels, acidity from acid run-off or leachate.

Cooperative Research Centre for Catchment Hydrology

Issues addressed include:

Water allocation. In many areas, the economic, practical, and environmentally sustainable extent of water harvesting has now been reached. In the Murray–Darling, for instance, a ‘cap’ on further water persions has been imposed.
Land-use impacts on rivers. Broad-scale afforestation is being considered for recharge control, but the consequent water-yield decreases may exacerbate the salinity problem downstream. Riparian vegetation and aquifer management can mediate sediment/pollutant delivery to channels. Preliminary research suggests that 90% of the nutrient flux problem can be solved by better management of 10% of the land area.
Climate variability. High climate variability in Australia gives rise to extreme fluctuations in streamflow. Better climate forecasts can reduce economic uncertainty.
Urban runoff quality. Urban stormwater is a major contributor to the pollution of rivers and bays. Runoff quality and quantity has been responsible for the degradation of most urban streams.
River restoration. There is tremendous enthusiasm to rehabilitate Australian streams, with at least $50 million being spent on this activity in Australia each year.

These issues are of concern to a water industry with revenues of $5000 million per year.

Murray-Darling Basin Water Resources Fact Sheet

Murray-Darling Basin Commission

Some of the water that would have been consumed by wetlands and the floodplain under natural conditions is now consumed by irrigation or is evaporated from reservoirs.

Using computer models, it has been estimated that, under natural conditions, almost 11,000 GL/year was consumed in wetlands, on the floodplains or by evaporation from the river surface and that only 12,890 GL/year or 54% of the runoff reached the sea.

Average Annual Water Balance for Murray-Darling Basin Rivers

	Natural Conditions (GL/year)	Current Conditions (GL/year)
Runoff	23850	23850
Inter-Basin Transfers	0	1200
perted	0	11580
Evaporated from Reservoirs	0	1430
Consumed by wetlands, floodplains, etc	10960	6970
Outflows to Sea	12890	5070
Outflow to Sea as a % of runoff	54%	21%

Water Recycling in Australia

Australian Academy of Technical Sciences and Engineering, May 2004

Australia is a large continent with only a small population to husband its land and water resources. Most of its rainfall soaks into the ground. Only 12% of its rainfall runs off and is collected in rivers. Much of this is in tropical monsoon areas with sparse communities and little development.

2006.06.13