THE SALINITY OF DJIBOUTI AQUIFER

Fresh water supplied to Djibouti town is essentially groundwater locat ed in the fractured Gulf and Somali basalt aquifers. About 30 wells (3 to 6 km inland from the sea) are exploited and provide water of rathe r poor quality (TDS between 1000 mg l(-1) and 2800 mg l(-1)). A sea wa ter interface has been recognized locally some 3.8 km from the sea at 35 m below sea level. However, a well at Hidka Gisiyed, some 11 km fro m the sea, also contains water with high salinity (TDS=14,000 mg l(-1) ) at depth. The over-exploitation of the aquifer and the high pumping rate are contributing to an increase in the salinity due to the intrus ion of sea water, as shown by the chemical results. The Hidka Gisiyed saline water is another possible source of saline water at depth. The isotopic results from part of the Djibouti aquifer have shown that cur rent recharge from local rain or surface runoff is occurring. An under standing of factors influencing the evolution of the salinity will all ow the better management of the aquifer. Copyright (C) 1996 Elsevier S cience Ltd