In this project IMDC developed a hydrological modelling platform for drought applications in Flanders. The models were applied to five pilot test basins. The toolbox produces drought maps for low flows and for soil moisture.
We started by comparing several existing drought model approaches, used in Flanders and internationally. Based on reported results, but also based on how easy each approach could be implemented in Flanders, three model concepts were selected for testing. These model concepts combined various model components: for interception, for runoff routing, for infiltration in the top soil layers and for interaction with groundwater layers.
The three model concepts were tested on the pilot catchments and used to simulate long-term periods of 50 years. The results were validated against historical drought year 1976 and the recent extreme summers of 2017 and 2018. The long-term simulation allowed to compute the long-term regime for river flow and soil moisture, and express it as drought maps with return periods. Such drought maps are useful for policy makers.
Using the 50-years regime the actual drought risk can be assessed. Is it dry for the time of the year? Are we nearing a historic extreme drought? Such information can be useful for operational managers to activate water saving measures: limitation of irrigation and navigation, rationing of drinking water, measures to safeguard the cooling of nuclear power plants, etc. A second application is the assessment of climate change impacts. The drought methodology was applied with perturbed climate inputs, for a dry scenario in 2050 and 2100. The results already confirmed that extreme drought in future will occur more frequently than today.