Abstract :
[en] In Belgium, climate projections consistently show hotter and drier summers, raising concerns for the future of groundwater resources. This study assesses how groundwater droughts—periods of sustained recharge deficit that lower groundwater tables and reduce river flows—could evolve in Wallonia, the southern region of the country, under global warming of +2°C to +4°C compared to the pre-industrial period, using percolation-derived indicators consistent with the latest IPCC scenarios.
Six plausible climatic scenarios were developed from two greenhouse gas emission scenarios (SSP3-7.0 and SSP5-8.5) and three global circulation models (MPI, MIROC6 and CMCC), explicitly addressing inter-model variability. These projections were used to estimate groundwater recharge through downscaling model MARv3.14 and the EPICgrid soil model. Recharge dynamics were analysed using four indicators based on 12-month cumulative recharge: mean recharge, minimum recharge, persistence of recharge deficits, and the ratio between recharge and current groundwater abstraction volumes.
Groundwater bodies were used as the unit of analysis to capture the behaviour of each aquifer system as a whole and to compare impacts across the region. Results indicate strong spatial variability but a clear overall pattern: at +2°C, uncertainties remain high, yet at +4°C, most scenarios indicate increased winter recharge and a reduction in the intensity and duration of groundwater droughts. The pressure on groundwater resources, expressed as the ratio between abstraction and mean recharge, also tends to decrease under high‑warming scenarios.
By expressing the results in terms of global warming levels rather than technical climate scenarios, this study provides a clear and accessible first basis for decision‑making and public communication on the future of groundwater resources. At the same time, it also shows that projected improvements in average winter recharge do not necessarily translate into lower risks for groundwater systems. It should be emphasised however that the analysis relies on constant abstraction rates, whereas climate change is expected to significantly alter water demand. More frequent summer droughts, in particular, may drive a substantial increase in agricultural irrigation withdrawals, which are currently limited in Wallonia. Neglecting such demand evolution could therefore lead to a serious underestimation of future groundwater stress, highlighting the need to couple recharge‑based climate impact assessments with prospective scenarios of groundwater use.
