Simulating spatial variability of groundwater table in England and Wales

Groundwater is a vital natural resource that affects human life and the environment. Groundwater supplies drinking water, supports irrigation for food production, and helps to sustain flow of water in streams and wetlands during dry periods. Therefore, it is important to assess the variability of groundwater resources and consider it in freshwater management. Numerical modelling is widely used for understanding the variability of groundwater table. However, there is still a lack of large-scale groundwater flow models. For instance, in the UK, groundwater modelling efforts so far have focused on aquifer to regional scales. A national scale model would aid the quantification of the available groundwater storage and the assessment of the impacts of climate change and anthropogenic activities on this crucial resource. In this study, we evaluate a numerical groundwater flow modelling approach for entire England and Wales. This model operates at one km spatial and one day temporal resolution. We force the model with precipitation and potential evapotranspiration, parameterise the subsurface using our estimation of transmissivity and specific yield based on available information, and simulate steady state groundwater heads over England and Wales. The results demonstrate that the model can reproduce spatial variability of groundwater table in the region. Because of a two-dimensional numerical representation of groundwater flow, the computational demand of this model is low, facilitating multiple simulations required for e.g., calibration, sensitivity analysis, and quantification of the impacts of environmental changes on groundwater resources.