DEFINING A BOREHOLE CAPTURE ZONE IN A COMPLEX SANDSTONE AQUIFER - A MODELING CASE-STUDY FROM SHROPSHIRE, UK

The sandstone aquifer in eastern Shropshire in central England is bein g extensively used for public water supply. However, rising nitrate co ncentrations in boreholes in the unconfined parts of the aquifer are a cause for concern. Edgmond Bridge, a new major abstraction, has recen tly been put into service. This study examines the hydrogeology of the sandstone aquifer in the area and uses a three-dimensional numerical groundwater flow model to represent the aquifer and to define the Edgm ond Bridge borehole catchment and distribution of flows within it. For an abstraction rate of 12 500 m3/d the catchment occupies an area of 18.7 km2 and is fed by direct and valley side recharge, induced river infiltration and lateral groundwater inflow.