Assessment of Groundwater Recharge in a Mediterranean Karst System Using Chelsa and MODIS Data

This study aims to quantify and map groundwater recharge in a Mediterranean karst aquifer in southern Italy over the period 2000–2018 by integrating analyses based on high-resolution climatological and remote sensing datasets. The approach uses annual precipitation (P) from the CHELSA v2.1 dataset, which provides ~1 km resolution climatological variables derived from downscaled ERA-interim reanalysis and ground observations. Actual evapotranspiration (AET) was obtained from the MODIS MOD16A3GF product (500 m resolution), based on the Penman– Monteith algorithm. GR was estimated through two methods employing groundwater recharge coefficients (GRCs). The first applied the APLIS model, a GIS-based empirical method specifically designed for karst aquifers, which determines a spatially distributed GRC as a function of five environmental variables. The second method used effective precipitation (P–AET) combined with lithology-dependent GRCs from the literature. Both recharge methods yielded slightly different GR estimates in terms of discharge rate at the basin scale, with values of 1.3 m³∙s-1 and 1.0 m³∙s-1 for the first and the second method, respectively. Locally, some spatial differences emerged due to methodological contrasts. Overall, the integrated GIS-based framework proved effective for estimating groundwater recharge in data-limited karst environments and demonstrates strong potential for application in other Mediterranean karst systems.