Hydraulic head response of a confined aquifer influenced by river stage fluctuations and mechanical loading

Abstract

Summary The response to river stage fluctuation of a drilled well penetrating a confined aquifer was simulated using a stream–aquifer interaction algorithm. Because the confined aquifer is overlaid by a water table aquifer, the algorithm was coupled with formulae used to correct the heads for mechanical loading. The coupling of stream–aquifer interaction and mechanical loading models was tried for the first time in this study. The test site was a drilled well installed on the Montalto Uffugo aquifer located at the Calabria University groundwater test field (Calabria region, south of Italy). This aquifer comprises a 44 m-thick sand bank bounded on bottom and top by clay layers and covered by a 7 m-thick sandy conglomerate, being adjacent to the Mavigliano River. Overall, the head changes caused by a river stage raise represented a contribution of 49.3–57.8% to the total head, while mechanical loading accounted for the remaining 50.7–32.2%. The loading was triggered by a sequence of short-spaced rainfall events lasting for a total of 167 days, which caused recharge to the unconfined aquifer thickening the water column by some 3.1 m.