Poitevin marsh is a typical example of anthropogenic activities influence on wetlands. One of the problems to be solved before considering preservation solutions, concerns the improvement of hydrogeological knowledge and water transfers between the marsh and Jurassic carbonate bedrock. This study aims to determine the hydrodynamic parameters of Quaternary and Upper Oxfordian aquifers in order to appreciate the water transfers between these aquifers and to better understand the hydrogeology of this area. Thus, pumping tests are carried out to determine the hydrodynamic parameters of the aquifers. The pumping tests interpretation carried out, allowed to highlight very low permeability of upper Oxfordian formations under Quaternary cover. As for the formations of Quaternary aquifer, obtained permeability coefficients are in the order of 10-7m/s to 10-6m/s with transmissivity values in the order of 10-6 to 10-5 m2/s and a storage coefficient in the order of 10-2. However, Quaternary formations are more permeable than Upper Oxfordian formations. On the time scale of the measurements, no hydraulic connection between Quaternary and Upper Oxfordian aquifers could be observed. The water transfers between these two aquifers would therefore be very limited.

The general downward trend in rainfall in West Africa since the 1970s has favored long periods of drought. The rainfall decrease has not only caused the depletion of water resources, but has also led to a disruption of the runoff regime of rivers. The objective of this study is to carry out a spatial and temporal characterization of the rainfall regime in the Bagoé watershed over the period from 1928 to 2000 in order to analyze its influence on the rivers runoff to better predict adaptation solutions. Statistical approaches and a GIS were used to characterize the rainfall variability which was then analyzed in relation to the runoff regime of rivers over the period from 1961 to 1986. The average annual precipitation recorded is 1397.04 mm with two dry periods (1928-1949 and 1976-2000) which frame the only wet period (1950-1975). A secondary rainfall rupture in 1949 and a principal rainfall rupture in 1975 were highlighted. The principal rainfall rupture in 1975 suggests a significant drop in precipitation from 1976 to 2000 marked geo-spatially by the predominance of 1100 mm and 1200 mm isohyets during the decade 1991-2000. This drop in rainfall led to a decrease in the water flow of rivers, also due to hydraulic activities in the basin. Adaptation solutions should therefore be found in the planning of development projects.