Excessive groundwater extraction for agriculture, combined with climate change, is depleting groundwater reserves and degrading their quality. This threatens both groundwater-dependent economies and ecosystems. In the Duero River basin in Spain, four groundwater bodies are in poor quantitative condition, and eighteen have a poor chemical status.

Within the European project STARS4Water (Supporting Stakeholders for Adaptive, Resilient, and Sustainable Water Management), a management system has been developed using the Groundwater Resource Availability Index (GWAI), reference levels, and management guidelines. This system aims to be universally applicable and flexible enough to adapt to various hydrological, climatic, and management contexts. The GWAI is designed to be calculated easily using data from standard monitoring programs, and its results should be easily interpretable by various stakeholders.

The GWAI calculation involves defining a ‘calculation period’ and determining the normalized slope of piezometric-level changes during that period. This is carried out iteratively, starting from the beginning of the historical piezometric data series, with the calculation window moving forward by one year in each iteration. This process reveals both the evolution of the index and its individual values. Management recommendations are based on the index's evolution over time, where negative GWAI values indicate resource depletion and positive values indicate increasing resource availability. These calculations were automated in a user-friendly spreadsheet program.

The GWAI was applied across the Duero River basin and in more detail to the Los Arenales–Tierra de Medina–La Moraña groundwater body, these areas being severely affected by resource quantity and chemical status issues.