Impact de la variabilité climatique et du barrage nangbéto sur l'hydrologie du système Mono-Couffo (Afrique de l'ouest)

Abstract

Many studies dealing with climatic variability in tropical Africa show a trend toward drought since the end of the 1960s. This drought, which affects West Africa and the Mono-Couffo hydrosystem, has had a marked effect on river flows, causing considerable decreases in daily, monthly and annual flows. However, since 1988, with the impoundment of the Nangbeto Reservoir, which coincided with the slight recovery of rainfall in the 1990s, there has been a change in the hydrological regime of the Mono River at Athieme. Statistical methods applied to time series of monthly rainfall and flow data for the period 1961-2000 enabled us to show that the rainfall deficits of the 1970s and 1980s generated deficits of flow, and consequently deficit in net recharge. However, with the slight recovery of rainfall (2%) from 1988 to 2000 compared to the sub-period 1961-1987, there is an excess flow of 37% on the Mono at Athieme, under an "artificial" regime since 1988; and no surplus (0.1%) on the Couffo at Lanta under a "natural" regime. © 2012 IAHS Press.