This study assessed ERA5 reanalysis on runoff, evapotranspiration, water table depth, and soil water content over the Benin basins at spatial scale and monthly time scale. The results showed that the reanalysis simulates well the peaks of mean runoff. It showed the best performance in terms of correlation (>0.50) for runoff, SWC, and ETR. But, the correlations were below 0.5 on the reanalysis for WTD with slight overestimation.

Knowledge of rainfall statistical behaviour is a prerequisite to designing rainwater drainage facilities. In West Africa, most practitioners use the Gumbel distribution regardless of rainfall statistical behaviour. This study quantifies biases induced by the use of the Gumbel distribution. It was found that the use of the Gumbel distribution instead of appropriate distributions leads to an underestimation (−45.9 %) of annual daily rainfall maxima and thus to an uncertain design of facilities.

Floods are natural disasters that widely affect people, goods, and ecosystems. Some efforts have been made in predicting floods at a short-term range. However, the usefulness of flood prediction increases as the time lead increases. This work investigated covariates useful for flood prediction several months ahead. Very good relationships were found between flood discharge and some climate indexes which could serve as a basis for seasonal flood forecasting in West Africa.