The assessment of drought duration, severity, and its impact on groundwater resources can be achieved through the integrated analysis of climatic indices and groundwater level fluctuations. This study investigates the effects of drought periods on groundwater within distinct sectors of the Castelporziano Estate aquifer. Utilizing data from two meteorological stations and the Estate's piezometric monitoring network, a comprehensive analysis was conducted. The availability of extensive thermo-pluviometric and piezometric records (1995-2024) facilitated the computation of the Standardized Precipitation-Evapotranspiration Index (SPEI) and the Standardized Groundwater Index (SGI), enabling the evaluation of their variations over the past 30 years.
Prior research has established the presence of a main aquifer, exhibiting seasonal fluctuations primarily driven by local meteoric inputs, with base flow sustained by contributions from the regional aquifer. The Coastal and Central sectors, mainly recharged by local precipitation, show a different decline in piezometric levels. Comparative analysis of the SPEI calculated for two weather stations, one situated along the coast and the other in the inland sector of the Estate, revealed significant variations, which prove decisive in the recharge processes of these sectors. The Coastal sector exhibited a consistent pattern of alternating wet and dry periods until 2016, followed by a sustained drought period extending to 2023. These fluctuations are reflected in groundwater levels, as evidenced by the SGI, which has registered continuous negative values since 2016, reaching its minimum values in 2024. In the Central sector, the SPEI indicates a protracted drought from 1999 to 2008, resulting in a persistent reduction of piezometric heads. Consistent negative SGI values since 2008 corroborate the enduring water deficit in this sector, with a discernible exacerbation observed in the last three years, correlating with the SPEI trend.