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Climate change has started to impact water resources in many regions and countries. Extreme eventshave become more frequent, with, in particular, severe winter or summer droughts that may affectgroundwater reservoirs which are essential for drinking water. The exceptionally arid winters of 2016and 2017 in Wallonia (Belgium) opened discussions on the necessity to develop tools and indicatorsthat allow quantifying such impacts and modelling the responses of aquifer systems to such events. In this context, the objective here is to describe the methodology that has been developed inWallonia (Belgium). The approach relies on numerical groundwater flow models used to obtaintrends in piezometric levels and groundwater balances using different specific drought scenarios.Modelling results are used to compute spatial maps of maximal piezometric drawdowns andrecovery times by comparing baseline and drought scenarios. Adopting a flow budget perspective,groundwater flow modelling results are also used to quantify indicators reflecting relative shifts inwater transfers between aquifer recharge, rivers, adjacent aquifers and exploited groundwater waterresources. The approach is illustrated using different strategic regional aquifers of Wallonia modelled usingvarious numerical groundwater flow models able to compute groundwater budgets and simulateboth the partially saturated and fully saturated zones of aquifers and the interactions with surfacewater courses. To assess the resilience of the groundwater bodies, three different scenarios weresimulated: the first entailed a series of years with typical recharge levels, the second involved threeconsecutive years with the same recharge as in 2016-2017, followed by years with standard rechargerates, and the third replicated the second scenario but follows the three arid years with anexceptionally wet year. Collectively these methodologies yield a better comprehension of drought impacts at a regional scaleboth in terms of spatial variability and large-scale water transfers.
Hutzemakers et al. (Mon,) studied this question.