Defra’s Demonstration Test Catchment programme (DTC) is investigating the diffuse pollution problem in three contrasting areas of the UK: the grassland dominated Eden catchment in the northwest of England (http://www.edendtc.org.uk); the arable dominated Wensum catchment in East Anglia (http://www.wensumalliance.org.uk) and the mixed farming of the Hampshire Avon and Tamar catchments in southern England (http://www.avondtc.org.uk). Component 1 of the DTC project included the selection and instrumentation of a series of target sub-catchments for hydrological, water quality and ecological monitoring using state-of-the-art sensor-web based systems together with more conventional approaches. Component 2 of the DTC programme will draw on this monitoring and experimental infrastructure to examine the impact of diffuse pollution mitigation measures. A range of mitigation measures agreed with key stakeholders in each sub-catchment will be installed and monitored. Rather than exploring solely how to minimise diffuse pollution, this project aims to understand the trade-offs involved in maintaining food production within sustainable farm businesses and delivering environmental improvements within soil and water.