Jan/Feb 2020 Corin Water Supply Reservoir (ACT)

The Orroral Valley fire in January and February 2020 impacted the Namadgi National Park (comprising the southern region of the Cotter catchment including Corin and Bendora water supply reservoirs). 1,951 hectares of Corin catchment and 137 hectares of Bendora
catchment were impacted by high severity fire. A risk assessment was completed to determine the management options in February 2020 and identified that the fire had been of a high intensity and had increased risks to water quality and water treatment needs.

The Cotter catchment bushfire was  followed shortly after by a high intensity rainfall event. Rainfall events following bushfires can have a significant impact on water quality, caused by increased rates of erosion, increased sediments and turbidity, and the introduction of a range of chemicals into the water supply. Rainfall following bushfires can release inorganic nutrients from burnt plant material and lead to an increase in phosphorus and other nutrients
entering waterways which can lead to  future algal blooms.

To minimise impacts to the ACT and regional water supply and in response to the Cotter catchment bushfire and rainfall event, Icon Water implemented the water quality event monitoring program, installed sediment traps to reduce sediment movement in drainage lines and deployed silt curtains on Corin and Bendora reservoirs to contain ash and suspended material.