ISOTOPIC AND GEOCHEMICAL IMPACT OF WATER RELEASES FROM THE SIDI SA?D DAM ON GROUNDWATER IN KAIROUAN PLAIN (CENTRAL TUNISIA)

摘要

Kairouan plain, big endorheic sedimentary basin of 3000 km 2 , contains the mostimportant aquifer of Central Tunisia. The importance of this aquifer is due first to itsgroundwater reservoir dimension, and then to the high recharge rates by the main wadis(Zeroud and Merguellil) floods and by direct rainfall infiltration. However, since thebuilding of the great dam of Sidi Saad on oued Zeroud to protect the plain againstflooding, natural recharge decreases. Even if regulated dam releases are carried out, aregular depletion of water level is observed due to over exploitation by high anthropicneeds. Geochemical and isotopic studies have been conducted in order to quantifythe efficiency of artificial recharge. A short time-interval sampling campaign (15 days)has been carried out during the dam release in May 2005 in order to follow up theimpact of dam water, whose geochemical and isotopic signatures are well identified ongroundwater characteristics.