Streamflow simulations for the extreme drought event of 2018 on the Rhine River Basin using WRF-Hydro

Recent drought events have significantly affected navigation through the Rhine River due to low water levels. This study assesses the capability of the Weather Research and Forecasting with Hydro extension (WRF-Hydro) to reproduce the 2018 extreme drought conditions in the Rhine River basin. While WRF-Hydro has primarily been used for flood studies, extreme low streamflow events have rarely been explored with hydrological models in this region.
We simulated Rhine River streamflow using ERA5 reanalysis dataset, and calibrated the model using 2016-2017 observed discharge values. Our modelling approach innovatively estimated essential hydrological parameters: infiltration scaling (REFKDT) and percolation (SLOPE) factors obtained from land cover information, and surface retention depth (RETDEPRTFAC) from the digital elevation model (DEM) derived slope. Statistical metrics showed median values of Nash-Sutcliffe Efficiency (NSE) and Kling-Gupta Efficiency (KGE) of 0.50 and 0.62, respectively. Modelling Lake Constance’s outflow was critical due to its influence on the upper Rhine basin. However, the lake module dampened streamflow excessively; therefore, excluding it produced more realistic hydrographs. ... mehrOverall, WRF-Hydro reasonably reproduced the variability and low water levels observed during the 2018 drought event, indicating its suitability for analyzing recent and future drought events in the Rhine River basin under extreme climate conditions.