Copyright 2000, Environmental News Network
December 21, 2000
By Julian Cribb

Scientists say Australia's declining water quality is caused by acidification and sodicity of soil and water systems.

The fate of Australia's landscape can be accurately charted by declining water quality, according to one of the country's leading water scientists.

"It is only now, however, that we are starting to build an integrated, nationwide picture of water quality which means we have lacked a complete picture of what is going on in our major catchments," says Graham Harris, chief of land and water for CSIRO, Australia's national science agency.

"Water links our whole landscape, from hill slope to estuary. By 'reading' the changing chemical composition of our water, we can assess how well or badly we are managing a catchment," Harris says.

Every water system has a point of no return when it is overloaded with pollutants of various kinds and collapses, Harris explains. Together with the National Land and Water Resources Audit and Environment Australia, Harris and colleagues are assessing how far down that road Australia's main water systems have gone.

By analyzing the chemical composition of water — how much sodium, calcium, iron, chloride and sulphate it contains — water scientists can construct an accurate picture of what is happening higher in the catchment. "That means we get early warning of problems before they become unmanageable," says Harris.

He warns of a looming future crisis caused by acidification and sodicity of soil and water systems. Land use in Australia has changed the hydrology and the biogeochemistry of the landscape, giving rise to a new set of chemicals that will be released from the land and infiltrate the country's waterways.

The implications for water quality may well be as great as that of salt, Harris says.

"At the moment, we are encouraging farmers to plant deep-rooted legumes like lucerne to reduce the risk of salinity," he notes. "The trouble is, these plants cause a buildup of acid in the soil. The area of acid soils in Australia is far larger than the area affected by salt and potentially a much greater threat to agriculture and natural ecosystems."

Water levels are monitored in an agricultural field in Western Australia.

By analyzing water quality, scientists can anticipate such problems. Water quality studies also reveal the level of suspended solids in murky waters caused by runoff from the catchment.

Turbid rivers, which once ran clear, are now losing their large water plants, making room for blooms of toxic algae.

Harris believes the balance between nitrogen and phosphorus in rivers relates directly to what is done in the catchment. When the balance tips too far toward phosphorus, it creates ideal conditions for algal blooms.

"Poor river management often makes matters worse by reducing the volume of river flows and increasing the residence-time of water in a section of the river. These still, turbid, phosphorus-rich waters all encourage algal blooms," he says.

Harris says several of Australia's river or coastal estuaries show signs of degradation. Two examples are Victoria's Gippsland lakes and the Swan-Canning estuary in Western Australia.

"We can expect more of these collapses of our aquatic ecosystems to occur if we continue to develop cities and farms in our coastal catchments," he warns. Error: Unable to read footer file.