Analysis of groundwater drought propagation in temperate climates using a water balance model and groundwater model

Droughts are mainly caused by periods of reduced precipitation and affect both surface and groundwater resources. This drought propagates to the different component of the hydrological cycle. Meteorological drought propagates to surface water and the unsaturated soil zone and to groundwater. This can result in groundwater drought. Groundwater drought can be defined as a temporary decrease in groundwater availability over a significant period of time. Groundwater droughts present a severe risk for water availability but have not received much attention in scientific literature compared to meteorological and hydrological drought. This research aims to develop and apply a method for simulating groundwater drought and its propagation in aquifers. The method was developed by combining a water balance model and a groundwater model for simulating groundwater drought. This research is carried out in the Dijle catchment in central Belgium, which overlies the vulnerable Brussels Sands aquifer. For groundwater drought analysis, time series of the three main groundwater variables, groundwater recharge (R), groundwater level (H) and groundwater discharge (Q), need to be available with a high spatial and temporal resolution. Although data on the groundwater levels (H) are available with a high temporal resolution, this is usually not the case for groundwater recharge (R) and discharge (Q) data. Therefore, groundwater recharge and discharge time series is simulated using a water balance model (WetSpass) in combination with a groundwater flow model (MODFLOW). Next, groundwater drought was evaluated using a threshold method. Threshold functions of the water table are Dtermined in the context of aquifer sustainability. An aquifer sustainability test is done using recharge-consumption time series in which no systematic trend is detected. The result of this research showed that droughts in the groundwater system are greatly attenuated and delayed.