ABSTRACT

Nowadays, water resources management is the key task in semi arid regions in order to fill the gap between water supply and the increasing water demand of different sectors, therefore, consistent tools are considered necessary to support the management and planning. In this framework, the Merguellil catchment is taken into consideration. It is situated in center of Tunisia, characterized by a semi arid climate but also by the most important groundwater resources. It is divided into two distinct areas by El Haouareb dam. The upstream catchment (1200 km2) presents a hilly topography and has diversified conditions of geology, morphology, vegetation and land use. The Merguellil downstream catchment is part of the very large and flat Kairouan alluvial plain that extends over about 3000 km2. Our research in the downstream part covers an area of 300 km2 close to the dam, west of the city of Kairouan. The agriculture is the main consumer with about 80% of the total water resources because of the continuous increase and intensification of irrigated area. The surface water represented by El Houareb dam can satisfy a very low portion of this demand; consequently, the groundwater is overexploited with a drawdown of its water level ranging between 0.25 m and 1 m per year. The public irrigated area is well controlled in terms of cropping pattern, surface related to each crop and their specific water demands and consumption rates. However, the private one is not very known particularly in terms of water volumes pumped from the aquifer which is representing the main pressure on the groundwater resources, therefore, sustainable management of the different water resources, while meeting as much as possible all water demands, is crucial.