A risk-based approach to prioritise catchments for diffuse metal pollution management.

Catchment management integrates a wide range of water management aspects taking into account the interaction between land-use and water quality. While most sources of pollution can be identified, monitoring and tackling diffuse pollution are difficult due to the abundance of its sources and pathways. As a result, the application of risk assessment of diffuse pollution at the catchment level has been limited. This study aimed to develop a risk-based approach to rank and prioritise catchments based on the need for managing diffuse metal pollution, using a multi-criteria evaluation framework. Source-pathway-receptor linkages were the basis for the selection of criteria and associated indicators. The methodology was applied to eight catchments located in the Humber River Basin District (RBD) that were comparatively evaluated, and difficulties in selecting weightings for the criteria used were discussed. Results showed that Don and Rother, Aire and Calder and Trent were the three catchments with the highest risk of diffuse metal pollution in this RBD. The findings demonstrate the potential of the proposed risk-based approach to inform more detailed investigations to follow and prioritise the need for investments on relevant programmes to prevent diffuse metal pollution in catchments where these are needed most.