Plaine alluviale du Niger supérieur et mare de Baro (Guinée)

Abstract

Among the succession of numerous small lakes along the floodplains of the Upper Niger and its tributaries, Baro lake in Upper Guinea is the best-known. It has been made famous by the annual fishing ritual that draws thousands of people to the banks of the Niandan. The hydrological functioning of the small lake was not known until an altimetric network was established for the water body and the surrounding plain and related to the flows of the Niandan. The processes via which the small lake is fed are now known and have been confirmed by a modelling test. Precipitation and the resulting runoff during the very rainy months of July, August, September and October account for the rise in the surface level of the small lake. The water level is sometimes constrained by high water in the Niandan, with which it is connected by a natural channel crossing the bank ridge. The prospect of the construction of Fomi dam means that questions should be asked about the fate of the small waterbody and the floodplain. Although farming around the small lake, and especially rice growing, can be conserved independently of the hydrological regime of the Niandan, the need for annual 'restocking' with fish means that a connection with the watercourse must be maintained. Fomi dam can provide a solution by means of artificial floods. Various scenarios are developed that aim at conserving fish migration and water levels that are satisfactory for rice growing while abstracting as little water as possible from Fomi reservoir. It is essential to build a gated fish pass or a pass with a cofferdam at the entry to the natural channel through the bank ridge in order to control the fall in water level.

Keywords

• environment
• resources
• floodplain
• hydrometry
• Upper Niger
• dam