Assessing Water Resource Vulnerability in an Agricultural Basin for Climate Change Adaptation

Understanding the impact of climate change and human activities on water resource vulnerability in agricultural watersheds is vital for developing climate adaptation strategies and ensuring food security. This study integrates a physically-based hydrological model with an improved Analytic Hierarchy Process (IAHP) to evaluate how climate change and human activities affect water balance and pollution loads, guiding adaptation measures for specific regions. The Soil and Water Assessment Tool plus (SWAT +) is employed to simulate water and nutrient balances in the Mishui River Basin (MRB) in southeastern China. Future environmental changes for three periods (2023–2040, 2041–2070, and 2071–2100) are predicted relative to a baseline (1997–2022). A multi-model ensemble approach, combining data from five Global Climate Models (GCMs) under two Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5), is used to reduce biases. The IAHP incorporates eight variables related to climate change, human activities, and pollution loads into the water resource vulnerability assessment. Results indicate a continuous decline in blue water (BW) and green water storage (GWS) in the MRB over time, while total nitrogen load consistently increases. Water resources are more vulnerable under SSP5-8.5, with BW decreasing by up to 41.9% and pollution load increasing by 71.1%, negatively impacting municipal water supply and irrigation. The IAHP analysis identifies nine high-priority sub-basins within the MRB with higher water resource vulnerability. In resource-limited scenarios, authorities can prioritize these areas for implementing water-related climate adaptation measures to ensure water security, food security, and ecological safety.