Time‐domain electromagnetic imaging of a clayey confining bed in a brackish environment: A case study in the Kairouan Plain Aquifer (Kelbia salt lake, Tunisia)

Abstract

AbstractThe semi‐arid Plio‐Quaternary aquifer of the Kairouan Plain is located in the central part of Tunisia. In this region, the main form of human activity is extensive agriculture. The few lithological logs in this area indicate that the aquifer is divided into two groundwater reservoirs separated by a confining clay layer. In the shallower groundwater reservoir, the electrical conductivity of the water is close to 1,200 mS/m, that is, 3 to 4 times higher than that of the deeper aquifer, which is currently used for irrigation. Recently, an increase in salinity has been observed, which is producing significant difficulties with irrigation. In order to determine the geometry of the confining clay layer and assess the potential connectivity between both reservoirs, time‐domain electromagnetic (TDEM) and vertical electrical soundings surveys were carried out. In the extremely conductive environment (electrical resistivities <10 Ωm) of the Sebkha Kelbia, the TDEM survey produced the first geophysical map of this near‐surface aquifer system.