The Sensitivity of Groundwater Recharge to the Rock Pore Connectivity Parameter in the Vadose Zone

Abstract— Data on groundwater recharge is necessary for solving different classes of hydrogeological problems. One of the recharge estimation methods is flow simulation in the vadose zone. Soil hydraulic parameters are used to estimate the recharge by flow in the vadose zone. One of these hydraulic parameters is the pore connectivity l. The estimated recharge sensitivity to the pore connectivity, especially under humid climate conditions, has not been studied thoroughly. In this study, the experimental values of soil hydraulic parameters of samples from two different sites with various landscape conditions and vadose zone structure (forest conditions on sand and field conditions on loam) have been used to estimate the groundwater recharge. The recharge was also estimated at l = 0.5 and at reported values of the l parameter for a certain type of sediment. According to the calculation results, the use of a fixed value of l = 0.5 leads to a significant overestimation of recharge under both forest and field conditions, which emphasizes the importance of experimental determinations of soil hydraulic parameters for the groundwater recharge estimation. According to the data from an analysis on water balance components, the increase in the estimated recharge with an increase in l is mainly related to a decrease in a top soil evaporation.