Large-scale risk screening of raw water quality in the context of drinking water catchments and integrated response strategies

Water resources provide multiple services, one of the most important the provision of drinking water, conventionally treated before public consumption as potable supplies. With increasing pressures from land use and climate change, there are advantages to be gained from considering raw water quality as a fundamental characteristic of the natural resource, and to anticipate emerging risks within the catchments rather than relying on treatment. This research proposes a large-scale, rapid risk screening of raw water quality based on catchment sensitivity to pressures as prerequisite to a more strategic inclusion of emerging risks in water resource and ecosystem management. Raw water quality observations from 154 surface water catchments in Scotland were investigated to determine the national baseline and to identify current pressures and underlying drivers. Patterns and spatial dependencies were investigated using principal component analysis, redundancy analysis, cluster analysis, and regression trees. These statistical approaches highlight the interaction between intrinsic catchment biophysical properties, land use and climate in characterising water quality risks and identify the focus for prioritising catchment interventions and risk-mitigation in the future. The emphasis on raw water quality will also support an ecosystem-based approach to increase catchment resilience, to ensure long-term supply of good quality drinking water while simultaneously creating wider benefits for society and the environment.