Are the Fouta Djallon Highlands Still the Water Tower of West Africa?

Abstract

A large share of surface water resources in Sahelian countries originates from Guinea’s Fouta Djallon highlands, earning the area the name of “the water tower of West Africa”. This paper aims to investigate the recent dynamics of the Fouta Djallon’s hydrological functioning. The evolution of the runoff and depletion coefficients are analyzed as well as their correlations with the rainfall and vegetation cover. The latter is described at three different space scales and with different methods. Twenty-five years after the end of the 1968–1993 major drought, annual discharges continue to slowly increase, nearly reaching a long-term average, as natural reservoirs which emptied to sustain streamflows during the drought have been replenishing since the 1990s, explaining the slow increase in discharges. However, another important trend has been detected since the beginning of the drought, i.e., the increase in the depletion coefficient of most of the Fouta Djallon upper basins, as a consequence of the reduction in the soil water-holding capacity. After confirming the pertinence and significance of this increase and subsequent decrease in the depletion coefficient, this paper identifies the factors possibly linked with the basins’ storage capacity trends. The densely populated areas of the summit plateau are also shown to be the ones where vegetation cover is not threatened and where ecological intensification of rural activities is ancient.

Special Issue “Multiscale Impacts of Anthropogenic and Climate Changes on Tropical and Mediterranean Hydrology”

“…The topics studied cover a large panel of hydrological questions. Many of them deal with the study of time series variability, rainfall [16], discharges [19,20], sediment transport [11][12][13]21], recession coefficient [22,23], climate change impacts [17,24], or anthropogenic impacts [2,11,20,21]. Drought is also a topic of notable interest in Mediterranean and tropical areas [23][24][25].…”

“…Going further inside the hydrological cycle, Descroix et al [23] discuss the recent dynamics of the Fouta Djallon's hydrological functioning. The evolution of the runoff and depletion coefficients are analyzed as well as their correlations with the rainfall and vegetation cover.…”

Final Responses to RC1

“…Printer-friendly version Discussion paper where vegetation cover is relatively stable (Descroix et al, 2020), anthropogenic impacts on runoff seem to be negligible (Faty, 2017) or not even mentioned in the updated Senegal River monography (Bader et al, 2014) and in the River Basin Master Plan (OMVS, 2011). The areas mainly concerned with massive land-use conversions are located downstream of Bakel, a region not considered in our analysis.…”

“…This is illustrated using the Senegal River Basin (SRB) as a case study. Headwaters in the SRB are still largely natural areas (Descroix et al, 2020;Faty, 2017) and the flow regime in the upper part of the basin exhibits regime-shifting behavior with departures from the inter-annual average over extended periods of time (Faye et al (2015); Paturel et al (2004); Dacosta et al (2002). These characteristics makes the SRB an…”

A new slippery frog (Amphibia, Conrauidae, Conraua Nieden, 1908) from the Fouta Djallon Highlands, west-central Guinea

“…(Young and Young 1992). The proximity to the Atlantic Ocean and south-westerly winds generate higher levels of precipitation than in other parts of West Africa (Kamara et al 2002;Descroix et al 2020). Together, the topographic and climatic complexity of Fouta Djallon creates a unique ecoregion with patches of tropical and subtropical moist broadleaf forests in valleys, surrounded by tropical and subtropical grasslands, savannahs and shrublands (ecoregions, sensu Dinerstein et al 2017).…”