Modeling runoff with satellite-based rainfall estimates in the Niger basin

Effective runoff modeling in the Niger basin has been hampered by inadequate and deteriorating amount of reliable observation stations. Satellite-based rainfall products have increasingly been considered an important component in addressing these data gaps. We compared the Global Precipitation Climatology Project (GPCP) one degree daily estimate and interim reanalysis data of the European Centre for Medium-Range Weather Forecasts (ECMWF) named ERA-Interim rainfall estimates with observed rainfall. The suitability of the two rainfall products for runoff modeling was also assessed. Rainfall data were averaged over a well gauged catchment (Sota) and compared. They were subsequently used to calibrate a hydrological model and their modeling efficiencies were evaluated. The better of the two datasets was subsequently used in regional simulation on 10 Niger basin catchments. GPCP rainfall estimates had good fit to observed rainfall with Nash values of 0.93, 0.94 and 0.84 for monthly, seasonal and daily climatological comparisons. River discharge simulated with the GPCP showed closer correlation with observed than the ERA-Interim. GPCP appropriately simulate river discharge in all 10 evaluated Niger basin catchments. Based on our findings, we proposed the integration of GPCP rainfall estimates in runoff modeling, especially in data scarce river basins