Erosion could affect water

Erosion could affect water

 1 August 2008

published by

Australia — The impact of the 2005 Wangary bushfire on the health of the Tod River was short lived but there is potential for other long-term impacts, an Environmental Protection Authority report has found.

The results of the EPA monitoring study released last month show the minor changes in water quality caused by the fire were short-lived and had no impact on the ecological health of the river because the majority of species in the river are quite tolerant.

The EPA studied the effects of the fire on the water quality and aquatic intervertebrates for a year after the fire, monitoring four different sites, including a section at Yallunda Flat, upstream of the fire ground.

Key changes to water quality were detected immediately after the fire from smoke, ash and burnt debris; and in June 2005 after the first major rainfall of the season, which washed debris and loose topsoil from the catchment into the river.

Monitoring found the increase in colour and nutrients detected the day after the fire was short-lived and water quality returned to normal levels after a few weeks.

Dissolved oxygen in the water was also at an all time low, which was attributed to seasonal variation exacerbated by the effects of the bushfire.

The June rainfall caused another increase in colour and an increase in the amount of organic carbon dissolved in the water.

The monitoring found no significant differences in the number or diversity of aquatic invertebrates after the fire, but it is possible there will be long-term changes to the river as an indirect result of the fire.

Changes in the channel from erosion due to the removal of burnt vegetation may lead to long-term changes in water chemistry or changes in the aquatic invertebrate community.

Continued monitoring through the EPA’s Ambient Monitoring Program will determine if long-term changes are occurring.

The report is available on the EPA website at

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