Large Scale Groundwater Modelling

Abstract

The goal of this report is to evaluate large scale groundwater modelling techniques to be used at the European scale for flood and drought forecasting. In the current LISFLOOD model, the groundwater component is represented by two interconnected linear reservoirs, with the outflow in some unit of time being proportional to the volume of water stored in the reservoirs. Simulations with this setup have shown to yield acceptable reproductions of the observed hydrograph, hence the model can be considered to be sufficiently detailed to predict floods. However, a good reproduction of river discharges does not imply that other hydrological variables (soil moisture, groundwater levels) or processes (percolation, plant water uptake, and retention processes) are well reproduced. LISFLOOD is not able to simulate the spatial distribution of groundwater levels, hence a comparison with groundwater observations is not possible. This document proposes possible ways to adapt LISFLOOD such that it can provide an estimate of the groundwater elevation in space and time. This would also allow distributed groundwater measurements to be used in the calibration and validation of the model, and to gain insight in the local hydrological processes and their representation in the model.