A modelling framework to estimate the impact of rewetting projects on agricultural activities in Flanders

The Flemish coalition agreement 2019-2024 places a strong emphasis on increasing our resilience to drought, including through the active use of resilient zones with (extra) nature to mitigate the effects of climate change. Neighboring agricultural activities can experience positive effects by buffering water in the landscape. However,  too shallow  groundwater levels can have consequences for the workability of the land and the crop growth itself.  This means that farmers and policy-makers do not only need to adapt to an increased occurrence of droughts, but probably also to the impacts of excessive soil water. Therefore, the project PEILIMPACT developed and applied model instruments, adapted to the Flemish conditions, to determine the impact of rising groundwater levels on the yield of common agricultural crops. The model SWAP-WOFOST, part of Water Vision Agriculture as developed for the Netherlands, was used for this purpose together with open data layers available in Flanders. The evaluation framework was based on an extensive literature review of the main points of attention in agriculture. Possible obstacles and concerns from main stakeholders (e.g. farmers) in different regions were also included in the evaluation framework. Results indicate that the impact of soil moisture conditions on crop yields is highly variable, both spatially and temporally. Areas with very shallow groundwater levels (>1 m) are negatively affected in wet years, but benefit in dry years. The opposite occurs in deeper groundwater levels, where more precipitation could compensate for the low groundwater contribution. The final report as well as the model instruments are freely available and documented so that application to specific locations where rewetting projects are planned is possible for all interested parties.