Post-fire land management and stream condition in the lower Cotter River catchment, ACT

Increased sediment and turbidity levels in water can influence physical, chemical and biological processes, potentially reducing the diversity and abundance of aquatic biota. Turbidity also impacts on the treatment costs for domestic water and sediment deposited in the water storages reduces storage capacity over time. All these effects are of particular relevance to the Lower Cotter Catchment (LCC) because the Cotter Reservoir is part of the national capital’s domestic water supply.  The objective of this study is to assess the effectiveness of land management intended to rehabilitate the LCC after severe fires in January 2003 burnt through a majority of this catchment.  Turbidity levels and biological condition of these streams has improved in response to rainfall events, when much of the accumulated fine sediment is flushed from the system and rehabilitation has reduced catchment sediment sources.  It is also evident that sites downstream of remediation areas are more degraded than upstream sites. However, remediation activities and revegetation throughout the LCC have had a positive effect on stabilising catchment surfaces and would be expected to show continued improvement with current management.