Estimation of spatially distributed groundwater potential recharge for the United Kingdom

The calculation of distributed recharge is necessary to drive numerical groundwater models used to manage and protect groundwater resources, to assess the impact of anthropogenic stresses and climate change, and to study the viability of technologies, such as exploiting the heat stored in the ground. A national-scale model allows policymakers and governmental decision-makers to set policy within the correct geographical context. However, many challenges are associated with building large-scale models, for example, the representation of processes on coarse grid resolution. This study presents distributed potential recharge values, calculated using the modified Environment Agency (EA)/Food and Agriculture Organization recharge algorithm. The model calibration is presented and the simulated potential recharge values and soil moisture deficit values are compared with estimates provided by the EA and the Meteorological Office (Met Office). Long-term average potential recharge values are very small in the east of the UK but they increase significantly towards the west and north, reaching values as high as 8 mm day−1 over the hills of Wales and Scotland. While this study highlights the need for further model refinement, the presented results are useful for assessing the potential recharge values at a national scale and for undertaking water resource studies, especially in catchments with unconfined/near-surface aquifers.