Using sediment budgets to prioritise erosion control in large river systems.

Targeting management actions aimed at improving water quality and habitat in large rivers is difficult. Resources for such actions are often limited; consequently, catchment works to reduce sediment supply need to focus on areas that will have the largest in-river effect. We describe how a sediment budget, developed using sediment transport modelling (SedNet), sediment tracing, and water quality monitoring, can be used to identify the primary sources of suspended sediment in the 29 000 km2 upper-middle Murrumbidgee Basin, Australia. It is shown that targeted erosion control will provide more than three times the reduction in suspended sediment export that would occur if the actions were implemented randomly. The results show that 70% of the sediment exported comes from 20% of the catchment area, and that channel bank erosion is the dominant source of sediment. The method has application in all large river systems where water quality and habitat sedimentation are issues.