A simplified method to determine specific yield (i.e., effective porosity) from hydraulic conductivity data obtained through pumping tests is proposed. This new method derives from a reprocessing of literature data and a subsequent calibration with results from pumping tests performed in different hydrogeological contexts. The use of the algorithm allows obtaining values of specific yield (Sy), which could be useful for the resolution of problems concerning the water balance and the transport of contaminants in groundwater. The proposed algorithm is applied to a large-scale area (Milan and its suburbs, northwestern Italy) to determine a map of the specific yield of a sandy-gravel aquifer and the effects on the estimation of water volumes stored in the subsoil from a hydrogeological point of view, considering about seventy years of measures. It is demonstrated that the great variation in water volumes reflects the socio-economic history of the territory.
specific yield, effective porosity, hydraulic conductivity, regionalization of hydrogeological parameters