Spatio-temporal Analysis of the Impact of Rainfall Dynamics on the Water Resources of the N'zi Watershed in Côte d'Ivoire

Abstract

This study aims to analyze impacts of rainfall dynamic on the water resources (surface water and groundwater) of N'zi watershed in Côte d'Ivoire. It justifies use of monthly average climatological data (rainfall, temperature) and hydrometric data of the watershed. The methodology is to interpolate by kriging rainfall, to highlight relationship between the spatial variability of rainfall and the surface water flow, and to evaluate groundwater recharge of fractured aquifers in the watershed. At the end of the study, it appears that the ten-year average rainfall of the N'zi watershed has decreased significantly. From 1233 mm during the decade 1951-1960, it lowered to 1074 mm during the decade 1991-2000. During the decades 1961-1970, 1971-1980 and 1981-1990, average rainfall is estimated at 1213 mm, 1068 mm and 1050 mm, respectively. From a spatial point of view, decrease in rainfall intensity was strongly felt in the central and northern localities, as in those located in the south of the watershed. Evolution of stream flow and rainfall is similar in the upper and middle N'zi, with maximum flow period in september corresponding mainly to the period of high rainfall. However, two peaks of different amplitude and a slight shift are observed between the peaks of rain and those of flow mainly in low N'zi. Water quantity streamed in the N’zi watershed during the period of 1972 to 2000 is of 40.7 mm. Water quantity infiltrated to reload aquifers of the watershed is evaluated to 47.6 mm, that is to say a volume of water infiltrated of approximately 1.7 109 m3.