Study sheds new light on bushfires

 Study sheds new light on bushfires

29 January 2008

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Australia — A study by CSIRO has helped shed light on the long-term effect of bushfires on water catchments. Understanding the impact of fires on catchment water yield is seen as critical to the long-term security of water supplies to cities, farms and the environment.

While forest fires can often result in an initial increase in water runoff from catchments, it’s the forests and bush growing back that can cause future problems for water supplies by reducing stream flows.

In the summer of 2002-03, bushfires burned through 700,000ha of forests in northeast Victoria.

This region supplies 38pc of the water that flows into the Murray-Darling River – the main source of water supply for much of Australia’s irrigated agriculture, the city of Adelaide and many towns along the river.

In a country where wildfires are prevalent and water supplies are at a premium, understanding the impact of wildfires on the water catchments is vital.

A study by CSIRO Forest Biosciences has helped shed light on the long term effect of bushfires.

Dr Richard Benyon of CSIRO Forest Biosciences says, “The study demonstrates a promising technique for catchment managers to more accurately predict changes in stream flow following wildfire, not only in northeast Victoria, but elsewhere in Australia.”

CSIRO’s remote sensing specialists analysed Landsat satellite images from before and after the 2003 fires to accurately map changes in the forest cover from which changes in water availability were predicted. Initially, the loss of vegetation, as a result of the fires, means the burnt areas use less water.

There is more water entering streams because it is not being used by the trees’ growth.

This short-term effect however, does not last.

As the forest begins to grow back, the young trees consume more water and substantial reductions in water yield from the catchments, can be expected over subsequent decades.

Victoria’s North East Catchment Management Authority Chief Executive, John Riddiford says the research provides a reliable method, for the first time, of predicting the impact of forest fires on water yield over large catchment areas.

“With the potential impacts of climate change, including the lower rainfall and increased risk of wildfire, it is important for catchment authorities to understand these possible impacts and to plan accordingly,” he says.

Dr Benyon says long-term impacts of wildfires on water yield is dependent on the type and condition of the forest before fires, the intensity of fires and the subsequent type, density and vigour of forest recovery.

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