Ecohydrological Distance and Water Stress: Sensitivity Analysis of Natural and Anthropized Flows in Mediterranean Basins under Climate and Human-Induced Changes

Water resources in Mediterranean regions face growing stress due to the combined effects of climate change, land use changes, and anthropogenic pressures. This study investigates the sensitivity of natural and anthropized river flows to these factors, focusing on basins in Tuscany (Italy) and the Valencian Community (Spain). The research uses advanced hydrological models (MOBIDIC and TETIS) to estimate natural and anthropized flows, quantify water stress, and introduce the Ecohydrological Distance Index (EcFI) to assess deviations from ecological sustainability in hydrological regimes.
The analysis emphasizes the impact of land use changes and anthropogenic pressures, such as water withdrawals and releases driven by population density and urbanization. Key indices, such as the PREX, which quantifies non-withdrawal pressures (e.g., land use and riparian alterations), and the Water Exploitation Index Plus (WEI+), which measures water stress by comparing abstraction to available resources, highlight critical areas experiencing significant water stress, especially during summer. These indices also provide insights into the drivers of ecohydrological imbalances.
A sensitivity analysis explores hydrological systems' responses to climate change (e.g., RCP8.5 scenarios) and human pressures, such as increased water demand from population growth and urban expansion. Results indicate a substantial reduction in summer flows (up to -50%) and a rise in water stress indices (e.g., WEI+) in upstream river segments. Land use changes, particularly urbanization and agricultural expansion, exacerbate water scarcity and ecological degradation, as reflected in the worsening of the EcFI and PREX indices.
This study offers a comprehensive framework for assessing the combined impacts of climate change, land use, and human pressures on water resources in Mediterranean basins. Integrating hydrological modeling, ecohydrological indices, and socio-environmental factors provides robust tools for sustainable water management. The findings support policymakers in developing adaptive strategies to mitigate water stress and protect aquatic ecosystems in a changing climate.