Surface-subsurface water interaction plays an important role in controlling groundwater chemistry, understanding this process is the basis for sustainable development. This study aims to investigate the surface water recharge from Lake Nasser into the groundwater of the Nubian sandstone aquifer in Tushka area. To achieve that, resultant water level change map was constructed and forty nine water samples were collected and chemically analyzed. The geochemical modeling code NETPATH was employed; distribution maps and cross sections of saturation indices for different minerals are carefully studied.
Results indicate that Lake Nasser is one of the main potential recharge sources to the Nubian sandstone aquifer and the distance to which the seepage process is ranging from 50 to70km. The saturation indices of calcite, dolomite, gypsum, anhydrite and silica minerals show negative values, decrease in the same directions of water flow, indicating sub-saturation and high potential for dissolution of such minerals. This can be referred to dilution caused by mixing of leaked surface- water from Lake Nasser with the groundwater in the Nubian sandstone aquifer. The contribution of recent recharge varies largely from 1% to 93% with an average of 48%, the mixing ratio is quite high and confirms the recharge from surface water of Lake Nasser.