APPLICATION OF HYDROGEOLOGICAL, STATISTICAL AND HYDROCHEMICAL METHODS IN THE STUDY OF THE HYDROLOGICAL SYSTEM OF DJORF TORBA DAM, (REGION OF BECHAR, SOUTH-WEST, ALGERIA)AMERI SARA, NABOU MOHAMED, MEKKAOUI ABDERRAHMANE AND ABDELAZIZ YAZID
This study consists of a multidisciplinary analysis of the hydrological system of Djorf-Torba dam and a quantification of the water infiltration from the lake into the water tables. Geological reconnaissance leads to the identification of a geologic environment previously favorable to infiltration and the existence of two aquifers; Fractured and karstified Turonian limestones (45m) and limestones with Quaternary travertines (12m), separated by a layer of marl (5m). The fluctuations in the auscultation piezometers highlight interferences between the superficial and underground waters. They are mostly consistent with variations in lake level. This observation is supported by statistics whose correlation coefficients (r) piezometers-water height in the lake range from 0.75 to 0.94. Piezometry established under water levels in the lake; Maximum (697.67m) and minimum (693m), generate two domes of water table recharge. In addition, at lake level> 695m, the lake water reaches the faults affecting the Turonian limestones and a doline on the right bank, the piezometers register rapid ascents, reflecting more ample infiltrations. The hydrochemistry supports this phenomenon of connectivity, the waters of the Turonian water table are more charged with mineralization due to the leaching of the rocks, and the variations in concentrations of chemical elements in this water table, are similar to the variations recorded in the Lake. The water balance and the calculation of the reserves regulating the quaternary aquifer suggest infiltration of about 17.56 Mm3 / year for the Turonian aquifer and 5.01 Mm3/year for the travertine.
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