Delineation and volume calculation of groundwater reserve based on AHP-EWM: a case study of Fuyang City, China

To ensure groundwater serves as a reliable water source during extreme drought years and major emergencies, this study proposed six principles for delineating groundwater reserve areas in Fuyang City as an example. A suitability evaluation index system for reserve areas was established. The combined analytic hierarchy process and entropy weight method (AHP-EWM), based on the minimum mutual information entropy theory, was used to determine the weight of each index, and indices were overlaid and spatially classified at a grid scale to delineate the reserve areas through Geographic Information System (GIS). The calculated groundwater reserve volumes for the three aquifer groups in Fuyang City are 166 million m3, 236 million m3, and 1.36 billion m3, respectively. A sensitivity analysis and a comparative water supply and usage analysis were conducted based on reserve volume calculation results, demonstrating the scientific validity and feasibility of the research. The findings address the questions of “where” and “how much” groundwater should be reserved in Fuyang City, providing a scientific and technical foundation for implementing strategic groundwater reserve policies and planning, significantly enhancing regional resilience against extreme water scarcity. Moreover, this study offers a transferable framework for groundwater reserve management that could inform similar initiatives in other regions.