Impact of rainfall infiltration on groundwater recharge of a deep quaternary aquifer

Abstract

Verification of recharge of groundwater in the deep Quaternary sand layers covered with leaky deposits of silt and clay has been implemented using mathematical modelling of the aquifer system in conditions of test pumping and during the 10 year exploitation of the Osijek well field Vinogradi. An analytical method for the identification of local parameters of the leaky aquifer is shown using the Excel program that enables usage of data from the relatively short term testing period, while at the same time suppressing external impacts. Boundary conditions and regional aquifer parameters have been verified by a numeric aquifer model, calibrated on the basis of three years of data from functioning field wells. The 96 mm average yearly recharge of rainfall infiltration into the aquitard was identified by validation of the model, based on information obtained from observation of groundwater levels in piezometers and in the pumped wells over a ten year period. At the end of the validation period, there was a 20 month break in pumping of the entire well field, and the measured recovery of groundwater levels provided an additional check on the results. Variation in the groundwater levels from particular layers, and water quality during exploitation are explained by the combined effects of closing of some of the well screens and the heterogeneity of the aquifer system.