Numerical modelling of catchment management options to manage nitrate concentrations in water abstracted from the Chalk aquifer, Cambridgeshire, UK

Abstract

Catchment management is favoured by the Water Framework Directive as a solution to the problem of rising nitrate levels in groundwater. The directive requires that member countries achieve a good, or improving, status in all water bodies by 2015. Currently, Cambridge Water relies on treatment or blending to reduce end-of-pipe nitrate concentrations to below the drinking water standard. The effectiveness of catchment management measures at 21 boreholes in Cambridgeshire was assessed with a combination of models, representing groundwater and soil zone processes. These sources are in predominantly arable catchments; they abstract from the Chalk aquifer, which is covered by Glacial Till in the south and east. Only seven sources showed a response to the catchment management scenarios within 40 years when compared with the current practice scenario. However, nitrate concentrations were not reduced at any sources by 2015 with the simulated catchment management measures. The seven sources that are most responsive to changes in land use or land management are those already affected by high nitrate levels. Catchment management may need to be used in conjunction with treatment and/or blending in the short to medium term so that Cambridge Water can continue to provide compliant drinking water to customers.