Abstract
Abstract. Local peoples from Niakhar in the Senegalese peanut basin highlight a dramatic increase of water access problems due to marked rainfall deficits and salinization of surface and ground water resources. The chemical quality of groundwaters is often critical because of the salinization process, whereas water surfaces, which should be used in such situations, are up early. More and more, lowlands and rivers beds are pervaded by salt crusts. Then the salinization of wells is increasing, leading to the extension of tans (salty of acidified soils). To study the impacts of climatic pejoration on the agroecosystems and on the living conditions of the populations, we carried out the analysis of the time series of the precipitations with daily and annual time steps from 1950 to 2015 on 6 meteorological stations, in situ measurements on 78 wells for an area of 311 km2, as well as local population interviews and field observation. The results confirm an important climatic break in the region in 1970. The long dry period, from 1970 to 2009, has increased the annual rain variability, decreased the number of rainy days per year. We confirm a real and large extension of well salinization, and salt crusting in the lowlands and the riverbeds. From the local people, it seems the process of degradation of the aquifers continues to progress from a large tidal event in 1984. The rainfall increase noted in the last decade does not seem to be enough to reverse the trend and to ensure both the rise of the piezometric level of the aquifers and the desalinization of surface and ground waters.
Highlights
Agricultural production, river discharge and groundwater productivity are related to the abundance and the regularity of rainfalls, mainly under semi-arid zones
The analysis of the standardized precipitation index (SPI) combined to the rain annual coefficient of variation and to the number of rainy days per year allow to conclude that in the whole studied area, the annual evolution of the rainfall is homogeneous on the studied period (1950–2016)
The dry period is effective in the whole Niakhar region from 1970 to 2009, characterized by an increase of the annual rain variability and a decrease of the number of rainy days per year
Summary
Agricultural production, river discharge and groundwater productivity are related to the abundance and the regularity of rainfalls, mainly under semi-arid zones. In the Sine-Saloum basin, the rainfall deficit from 1971 to 2000 is more than 300 mm compared to the period 1941 to 1970, as a reduction of the annual rainfall of more than 30 % in the estuarine part and 15 % in the upper basin (DGPRE, 2014) In this region, this altered climate condition has led to a decrease of river flows, a drop of groundwater table, a drying up of the wells, a desiccation of the pools which are very important for the breeders, a significant degradation of the abiotic environment in particular with the salinization of soils, waters and wells, and by a considerable degradation of the vegetation cover (Sagna et al, 2015)
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