Impact of groundwater level rise and humidity on agricultural land in Flanders

Context and research question Suppose that we raise the groundwater levels in certain places, thus increasing the soil moisture content. What impact would that presumably have on the yield of common agricultural crops in Flanders? This research question is addressed in the PEILIMPACT project. In order to mitigate the effects of climate change, the Flemish coalition agree- ment 2019-2024 strongly emphasizes increased resilience to drought, including through the active deployment of a resilient space with (additional) nature. Agricultural activit- ies can experience positive effects through the water being buffered in the landscape. Yet, there are also possible negative effects: if the water level is too high, this could compromise the ability to work the land, could negatively affect crop growth and in- crease disease pressure on crops, as well as the availability and leaching of nutrients to surface and groundwater. Research methodology Through targeted dialogue moments with individual farmers from different agricultural regions in Flanders, we obtain experiential knowledge about the effect of too high or too low groundwater levels on certain crops. We detect possible obstacles to their agricultural activity and important effects on yield, both positive and negative, and their causes. The model must help to determine “sufficiently favorable” groundwater levels for agriculture given a number of parameters. Simple guide values are too gener- alistic, because suitable groundwater levels for agriculture depend on the type of soil, the crop and the depth of the roots, the time of year, and so on. To determine feasible water level increases for a specific situation, model calculations for a range of different weather scenarios and for the crops grown in a specific location, is needed. In this study we determine the effect of groundwater levels in crop yield based on open data layers in Flanders. Relevance An evaluation framework for the impact of groundwater level increases can be used to calculate the effect of water management decisions and to link these to compensation for affected landowners as well as to discuss sustainable solutions with farmers and nature managers. The framework can also assist farmers in crop selection etc. on a particular field with its specific soil and meteorological context. This project was carried out by the Flemish Institute for Agricultural, Fisheries and Food Research (ILVO) [Diana Estrella, Sarah Garré, Tom De Swaef] i.s.m. KWR Water Research Institute [Ruud Bartholomeus] and Wageningen University & Research (WUR) [Martin Mulder, Mirjam Hack-ten Broeke