Effects of underlying fractured bedrock on an unconfined aquifer hydraulic behavior

Abstract— Unconfined aquifers may underlain by fractured bedrock. In these cases the stored and transmitted groundwater of underlying fractured aquifer affects overlying unconfined aquifer drawdown and its sensitivity to hydraulic parameters. In these cases, using unconfined aquifer analytical models e.g. Neuman [12] are no longer valid as the bedrock assumed to be impermeable in these models. In this work, the analytical model developed by Sedghi and Samani [8] is used to show errors arising from the neglect of underlying fractured bedrock in the analytical models used in unconfined aquifer parameter estimation. We also show the effects of underlying bedrock on the sensitivity of dimensionless drawdown to important and hard to estimate parameter, specific yield. As stored and transmitted water in the underlying fractured aquifer affect drawdown sensitivity to specific yield, the optimum location of piezometer to better estimate specific yield is suggested using the normalized sensitivity map. Keyword; ; ; ; .