Sustainable Water Resource Management in the Merguellil Watershed (Tunisia): Assessing the Impacts of Climate Change and Human Activities Using the WEAP Model

In semi-arid regions, the growing demand for water, particularly for irrigation, accelerates the overexploitation of water resources, often leading to severe scarcity that constrains sustainable economic development. This issue is particularly acute in the Merguellil watershed in central Tunisia, where the impacts of climate change exacerbate the challenges. This study employs the Water Evaluation and Planning (WEAP) system model to analyze current and future trends in surface and groundwater resources in the Merguellil watershed, assessing the combined effects of climate change and human activities on these resources. The primary objective is to identify critical thresholds, evaluate sustainable solutions and guide adaptive water management strategies. An essential element of the study is estimating the demand for irrigation water in the Kairouan plain using high-resolution Landsat 8 imagery to calculate crop evapotranspiration (ETC). Once the required input data from 2000 to 2020 are introduced in the WEAP model, the impact of different scenarios (Climatic and anthropogenic) for the actual and future water balance were evaluated until 2050. The simulation results under the RCP 4.5 climate scenario indicate a significant decline in aquifer levels across the basin; the Kairouan aquifers being particularly impacted. Additionally, scenarios involving the expansion of irrigated areas show a substantial increase in agricultural water requirements. To address these pressing challenges, this study explores multiple management strategies, including improving the efficiency and satisfaction levels of public irrigation systems, optimizing reservoir management during drought periods, and interconnecting existing water infrastructures. Notably, the findings highlight the importance of gradually increasing water transfers to the El Haouareb Dam to meet irrigation demands effectively. Finally, we conclude by emphasizing the importance of proactive and adaptive measures in order to mitigate the adverse impacts of climate change and human activities on water resources in this area. This study highlights the need for integrated, resilient, and sustainable water management practices to ensure the long-term viability of water resources in this vulnerable region.