Assessment of water table depth and soil water content Estimates from ERA5 reanalysis in Benin (West Africa)

The validation of hydrogeological distributed models in western african countries is limited by the quality and availability of point station data measured in-situ. Climate models, satellite and reanalysis data have been suggested to overcome this limit. Here, we assessed the quality of ERA5 reanalysis on water table depth (WTD), and soil water content (SWC) over the Benin basins at spatial scale and monthly time scale. The single-levels version with 0.25° x 0.25° resolution (ERA5) and the land surface version with 0.1° x 0.1° resolution (namely LAND) were compared with point station data using the correlation performance evaluators and the Mean Absolute Error (MAE). The results showed that ERA5 and LAND reanalysis present well the water planes of Benin (WTD =0m). Outside wetlands areas, both reanalyses slight overestimation the WTD (MAE of ERA5=4.73m vs. LAND=3.13m. The SWC between 0-7 cm; 7-28cm and 28-100cm presented on both reanalyses are well in line with observations for all stations and on a monthly scale (correlation sometimes > 0.85 for LAND and 0.83 for ERA5). We recommend the use of LAND for validation of hydrogeological distributed models in Benin. Correcting the variables of these reanalyses could improve their performance.