QUALITY CONTROL OF SURFACE WATER QUALITY: A CASE STUDY OF THE LAKE ALEG IN MAURITANIA

Water quality observation data were collected from 10 representative monitoring sites located in the main stream of the Aleg's lake, Mauritania and its major tributaries between 2016 and 2018. The Brakna region (Aleg, Mauritania) is symptomatic to the general State of the Mauritanian Sahel, which was hit by a desertification that has been steadily increasing over the last decades. It results in a strong reduction, or even a local loss, of the potential agro-sylvo-pastoral production, leading to a genuine risk for the populations' survival or at least an aggravation of poverty. All this has not been without impact on a highly deteriorated environment and a lastingly mortgaged socio-economic development. In the light of this situation, we will be studying the hydrochemistry of the surface water of Aleg's lake in Mauritania. After many years of domestic exploitation, both industrial and agricultural, besides climate change, it is interesting to ensure water's quality. With this intention, we have tried to realise a physicochemical analysis, an evaluation, to have an idea on the evolution of the chamical facies of Aleg's lake's water. For this, a sampling has been done for both dry seasons and wintering of the year 2017 at the 10 stations on both of the lake's shores. The following physicochemical parameters are: T, pH, C.E, Ca2+, Mg2+, Na+ , K+ , Cl- , HCO3- and SO4-2 . These measures include the volumetric and the spectroscopic analyses. The statistical exploitation of the results and their comparison with the interpretation of Piper's diagram, the results of the present study have shown that the lake's water in general has a bicarbonate calcic and magnesian facies for water at all sampling stations. As well as the evaluation of the analysis of the physicochemical parameters of the water of Aleg's lake presented in this work, it showed that the pH is close to neutrality: 7.43, the mineralization is average due to the conductivity presenting and average of 313.5 µS/cm. the average values of the calcium, magnesium, sodium and potassium ions are, respectively, 28.75 mg/L, 21 mg/L, 28.92 mg/L and 18.54 mg/L and the sulphate contents of the samples are very low: 22.13 mg/L. these results meet the FAO norms.