Modelling response of groundwater nitrate concentration in public supply wells to land-use change

As Britain's second largest aquifer, the Sherwood Sandstone is confronted by the threat of high nitrate concentrations caused by intensive agricultural activities. The aim of this study is to investigate the response of groundwater nitrate concentration in a public supply well to land-use change, discussing the effect of land-use change in tackling agricultural nitrate pollution in the aquifer. Six land-use scenarios were examined in predictive simulations of groundwater nitrate concentration. Groundwater flow modelling (MODFLOW) and mass transport modelling (MT3DMS), incorporating results from an export coefficient model, were used to predict groundwater nitrate concentration in the public supply well by 2025. Results from the quantitative comparison of scenarios revealed that the greatest decrease in nitrate concentration (35%) by 2025 in the public supply well was associated with the entire target zone being covered with forest, whereas a decrease dependent on the application of best agricultural practice achieved no more than a 20% reduction. It is concluded that the modelling framework constructed in this study is a useful tool for assessment of the impact of changes in land use and management on groundwater nitrate concentration in public supply wells.