Hydrogeological characterization of Terminal Complex aquifers using geoelectrical investigation to enhance groundwater prospecting in the arid environment of Chetma-Biskra, South-East of Algeria.

Abstract

Due to occurrence of groundwater in deeply buried aquifers with low recharge, water scarcity in Saharan and arid environments in Algeria was diagnosed in many populated regions such as Biskra. Constituting a transition hydrogeological area between the folded Atlasic domains in the North and the Saharan flat in the South, Biskra contains large groundwater resources in the terminal complex aquifers. 93% of water needs provides from groundwater and only 7% from surface water. But this region is facing to an acute shortage of water supply for domestic and irrigation demands because of the unappreciated groundwater prospecting and potentiality. Using an integrated approach which enclose geophysical investigation combined to geological and hydrogeological contexts at Chetma area, a deep structural form with significant hydrogeological features was highlighted and confirmed the accumulation of groundwater. Two resistant limestone anticlines called Droh anticlines corresponding to a piezometric dome and a syncline filled with conductive deposit materials were identified. Maastrichtian limestone consists of cracked and thick aquifer formation about 200 to 350 m, together with marl limestone and limestone of the lower Eocene forms a complex aquifer. Pumped boreholes, deep about 400 m, present a mixture of water giving large flow rate ranged from 25 to 90 l/s and constitutes a pattern produce zones of water accumulation. Nevertheless, at 300 m of depth, flow rate offers an average of 40 l/s and capturing mainly Maastrichtian limestone aquifer. However, synform geometries involving clay and marl formations have no hydrogeological interest. Occurrence of potential aquifers mostly identified in fractured zones was confirmed. This study gives insight to enhance groundwater prospecting and mobilization for 2030.