Nick Paling, Westcountry Rivers Trust.

If we can determine which pressures are exerting negative impacts on the water quality in our aquatic ecosystems and identify their sources in a catchment, then we can develop a programme of tailored and targeted interventions to remove these sources and disconnect their pollution pathways.

For many point sources of pollution the scale of their contribution to the pollution load in a watercourse can be easily characterised and regulatory and technological measures can be implemented to mitigate their impact. In contrast, the various sources of diffuse pollution in catchments are far harder to identify and individually their impacts are too slight or challenging to quantify for regulatory measures to be taken. Despite these challenges however, there is now a wealth of evidence and data which do allow these diffuse sources of pollution to be identified and their contributions to the overall pollution load to be estimated.

In recent years, numerous methods have been developed to identify the sources of suspended solids and the dynamics of sediment transport in rivers. These methods, which vary greatly in the spatial scales at which they can be applied, include; (1) fine sediment risk modelling, (2) sediment load water quality sampling, (3) sediment-focused river walkover surveys, and (4) source apportionment using fluorescent, chemical and genetic signatures.

The integration and assessment of these different sources of evidence helps us to quantify the scale of the pollutant pressure being exerted on an ecosystem, characterise from where in the catchment it is being derived and to target the delivery of a programme of catchment management interventions. Though adopting this evidence-led approach we hope to create plan that is; (1) strategically targeted and timed to achieve the greatest amount of benefit, (2) integrated to adopt a blend of different measures tailored to each situation and objective, (3) fully costed and funded by the most appropriate stakeholder, and (4) balanced to deliver improvements for the river, but not at the expense of food production or the farmer’s business.

In this presentation, I describe how we have generated pollutant risk maps using the SCIMAP modelling framework and how these maps have been incorporated into the data and evidence we use to target and tailor our catchment management plans in the South West of England.

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