Impact of dam construction on the hydrological regime and quality of a Sahelian lake in the River Senegal basin

Abstract

The direct and indirect impact of the recent hydraulic installations on the River Senegal on Lake Guiers are obvious. The hydrological regime of the lake was very irregular before the dams were brought into operation. The lake is now characterized by very stable water levels. These new conditions prevent cultivation of traditional recession crops which have been replaced by irrigated crops. The water quality of the lake has been modified. Mean salinity has decreased and the significant interannual and intraannual variations noted before 1986 are now far less pronounced. The new hydrological regime of the lake and its low salt content have encouraged aquatic vegetation to grow rapidly. This vegetation used to be controlled by the periodic partial drying of the flooding zone and specific water quality conditions at certain times of the year. Pistia stratiotes and Typha australis are now increasing rapidly. This proliferation of aquatic plants has no doubt accelerated the rapid spread of schistosomiasis, which now affects 80% of the population of some lakeside villages. The management of Lake Guiers requires an integrated quantitative and qualitative approach. A water management model has been perfected. It permits an assessment of the effects of various quantitative reservoir management options on the salinity of the water. © 1997 John Wiley & Sons, Ltd.