The Superposition of Climate Change and Anthropogenic Pressure Threatens Blue Water Resources in Tunisia

The combined effects of climate change (CC) and anthropogenic activities, particularly land use/land cover change (LULCC) and irrigation on water resources in North Africa remain insufficiently explored. This study presents an integrated, data-driven assessment of surface and groundwater responses in a representative agro-hydrological basin in northern Tunisia, characterised by a reservoir used for irrigation (Chiba watershed) under both historical and projected CC and LULCC scenarios. Using the SWAT hydrological model across five periods (P0: 1993–2014; P1: 1993–2003; P2: 2004–2014; and projections for the 2030s and 2050s), we integrated bias-corrected climate data from CMIP6 general circulation models (GCMs), as provided in the IPCC's Sixth Assessment Report, with seven land-use maps derived from remote sensing to simulate the impact of climate and anthropogenic drivers on blue water resources and reservoir used for irrigation. Key findings reveal a critical hydrological threshold regulating irrigation-induced groundwater recharge: monthly rainfall must exceed 15–25 mm, and reservoir storage must remain above 1.5 Mm3 to ensure groundwater recharge. Historical conditions supported sufficient irrigation-induced recharge, but future projections indicate reservoir decline, threatening water sustainability. This study highlights the fragile balance between rainfall, storage, irrigation, and recharge processes, emphasising the exposure of Mediterranean systems to climate variability. These dynamics demonstrate that without appropriate management interventions, future hydro-climatic conditions may threaten both water security and groundwater sustainability. In this context, adaptive water governance becomes crucial to maintain sustainability and ecosystem resilience under future hydro-climatic and management constraints.