Demonstration test catchments : the role of hydrogeological conceptual modelling

Agricultural diffuse pollution, particularly from nitrate and phosphate, is a significant problem in the UK and is the focus of the national Demonstration Test Catchments (DTC) study — a UK Government initiative. The DTC programme is providing evidence for investigating how on-farm mitigation measures can reduce the impact of agricultural diffuse water pollution on ecological function. This will involve studying how such measures affect pollutant concentrations in so-called receptors, such as the streams which drain the catchments. It is therefore important to investigate how water moves from the land surface to the receptors and in particular to quantify the amounts and timescales involved in the different water flow routes. The DTC catchments are the Eden, the Avon and the Wensum and groundwater flow is a significant component of main river flow in all of the catchments, ranging in overall terms from around 50% of river flow in the Eden to 90% in the Avon. It is therefore important that robust conceptual models of the groundwater flow systems of the catchments — and in particular of the monitored sub-catchments — are developed. BGS is contributing to the creation of DTC groundwater conceptual models in all three study catchments. The BGS work is funded principally by NERC and by DEFRA.