Impact of Climatic and Anthropogenic Scenarios on Water Resources Management Using the WEAP Model: Case Study of Merguellil Watershed

In semi-arid regions, the water scarcity and rainfall irregularity in time and space with increasing of water demand related to different sectors have led to overexploitation of surface and groundwater resources mainly because of irrigation needs. This is the case of Merguellil Basin situated in the central of Tunisia. To analyze the actual and future water balance of the Merguellil watershed, and to identify critical trends and thresholds and effective solutions, a water evaluation and planning system (WEAP) was used. The main objective of this study is to analyze climate, anthropogenic, and management changes scenarios in the Merguellil watershed, using remote sensing tools. Climatic scenarios were tested for RCP4.5 where temperatures are expected to increase by an average of one degree by 2030, then by an average of 1.5 °C until 2050. These increases could reach 1.3 and 2.3 °C on average, respectively, at the 2030 and 2050 horizons with the RCP8.5 scenario. Simulations show a rapid decrease of the water storage in the four aquifers in the basin especially for Kairouan aquifer under the different scenarios. Moreover, the combination between the increase of irrigated area and the two climatic scenarios will make the situation more difficult by 2050. A management solution was tested to improve the water balance situation in the area which is the interconnection between El Haouareb and Sidi Saad dams. Results show that an increasing volume over time of the transferred water to El Houareb dam according to the irrigation water needs in the public irrigated area is necessary to make this solution more efficient.