Bushfires not only have the power to destroy crops, native bush, livestock and homes, they can also affect the water quality in our creeks and rivers. These impacts can range from short-term changes noticed immediately after the fire to long-term impacts that can last for many years.
Fire can result in an increase in nutrients and sediment in rivers. Nutrients can be released from sediment or debris from burnt vegetation, or come from ash and smoke that can be carried to the water by wind or through runoff following rain.
The volume of runoff from a catchment can increase after a fire and this can lead to increases in the amount of sediment entering the river. This excess runoff has the capacity to change the channel structure and flow, through bank erosion and sediment deposition. In some cases this alteration may be beneficial, such as providing additional habitats or refuge pools in the river, particularly for fish.
The EPA monitored the recovery of the Tod River on the Eyre Peninsula for one year following the bushfire on 11 January 2005 in which more than 80,000 hectares of land north of Port Lincoln were burnt. The impacts of the fire on the water quality were found to be minor and very short-lived. As the aquatic macroinvertebrates in the Tod River are quite tolerant and able to withstand the brackish and ephemeral nature of this river, they were not affected by the minor changes in water quality due to the bushfire. More long-term changes to the river will become apparent in the future. Additional monitoring of the Tod River, through the EPA's Ambient Monitoring Program, will enable us to determine if there are long-term changes.