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EN
Analysis of groundwater quality in the alluvial aquifer of the lower Soummam Valley, North-East of Algeria, was realised through the application of multivariate statistical methods: hierarchical cluster analysis (HCA) in Q and R modes, factorial correspondence analysis (FCA), and principal component analysis (PCA), to hydrochemical data from 51 groundwater samples, collected from 17 boreholes during periods of June, September 2016 and March 2017. The objectives of this approach are to characterise the water quality and to know the factors which govern its evolution by processes controlling its chemical composition. The Piper diagram shows two hydrochemical facies: calcium chloride and sodium bicarbonate. Statistical techniques HCA, PCA, and FCA reveal two groups of waters: the first (EC, Ca2+, Mg2+, Cl-, SO42- and NO3-) of evaporitic origin linked to the dissolution processes of limestone rocks, leaching of saliferous soils and anthropogenic processes, namely contamination wastewater and agricultural activity, as well marine intrusion; and the second group (Na+, K+, and HCO3-) of carbonated origin influenced by the dissolution of carbonate formations and the exchange of bases. The hermodynamic study has shown that all groundwater is undersaturated with respect to evaporitic minerals. On the other hand, it is supersaturated with respect to carbonate minerals, except for water from boreholes F9, F14, and F16, which possibly comes down to the lack of dissolution and arrival of these minerals. The results of this study clearly demonstrate the utility of multivariate statistical methods in the analysis of groundwater quality.
EN
A failure analysis of Babar dam on the El Arab River was performed to highlight the impact of flood wave and velocities on the four villages downstream of the dam; Hella, Khérenne, Chebla and El Oueldja. The simulation of wave propagation along the El Arab River under several scenarios was performed by the hydraulic HEC-RAS model. This model is dedicated to the description of floods at the dam following a breach in the dike. The main factors considered in this simulation include the level of flood water, the flood hydrograph, and the typical scenario for this breach. The flood risk analysis revealed that the maximum of flood wave flow registered at the breach is (Qmax = 9253.02 m3∙s–1), and is beginning to mitigate downstream of the dam along the El Arab River where it reached at the last village with a low flow (Q = 1110.64 m3∙s–1). This simulation allowed drawing the risk map which showed the areas threatened by flood wave resulting from a total failure of the work, and consequently required a plan of security measures to moderate as much as possible the consequences of floods. A sensitivity analysis was conducted to approach the parameters of impact of the breach on the dam failure scenario. It was confirmed that these parameters as formulation time, breach width and side slope have a great influence on the dam failure scenario with the four adjustments (±20 and ±50).
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