Analysis of the temporal variability of runoff in Ivory Coast: Statistical approach and phenomena characterization

The runoffs at four Ivory Coast hydrometric stations (monitoring flows from an area covering between 5930 and 66500 km(2)) were analysed with a set of statistical methods for the detection of breaks in the time series. The variables studied were the annual mean discharge and some characteristic discharges. From a quantitative standpoint, the existence of a clear break in the series of annual mean discharges at the beginning of the decade from 1970, the date from which the runoffs decrease significantly, was noted. A more qualitative study of the results showed that low flows were more affected than high flows by this variability of the regime. This fluctuation appears to be in accord with the drought phenomena observed during the same period in the Sahel, to the north of Ivory Coast.