Assessing response times of an alluvial aquifer experiencing seasonally variable meteorological inputs

Abstract

This study aims to assess the spatiotemporal distribution of the response times of an alluvial aquifer experiencing seasonally variable meteorological inputs and to investigate the aquifer characteristics that influence its response times. The sliding cross-correlogram approach was used in this study to correlate the amount of water infiltrating the subsurface with changes in water table levels that were monitored at six piezometers. The results showed a significant variation of aquifer response times over the study area; this finding indicates that the hydraulic behavior of an aquifer may differ from one location to another within the same aquifer. Aquifer response times were found to be influenced by the variations of the vadose zone thickness. These variations, however, were not observed to be a significant factor controlling the spatiotemporal changes in the aquifer response times. Instead, it was the intensity of the vertical inflow events and the local recharge rate that were found to exert an impact on the spatiotemporal variation of the aquifer response times. It was assumed that large amounts of vertical inflow increase the soil's volumetric water content above the water table, leading to higher values of hydraulic conductivity of unsaturated soils, thus contributing to shortening aquifer response times. A better understanding of the effects of aquifer characteristics on aquifer response times is useful for groundwater resource management.