Improving Water Table Kinematic Conditions With Unsaturated Flow Insights

Abstract

Analytical models interpreting aquifer pumping test data often rely on water table kinematic conditions that assume instantaneous gravity drainage, leading to underestimation of specific yield during the drainage process. This study derives a new water table condition based on a coupled saturated-unsaturated flow model that fully accounts for both unsaturated and saturated flow dynamics. The new condition incorporates the hydraulic properties of the unsaturated zone, providing a more accurate representation of physical processes while maintaining mathematical tractability. Applied to a groundwater flow model for a pumping problem, the drawdown solution is derived using integral transformations. The proposed model is validated using field data from a series of pumping tests at the Boise Hydrogeophysical Research Site in Idaho. The results demonstrate that the new water table condition provides more reliable estimates of specific yield, effectively addressing the underestimation issue associated with existing models. Moreover, the model requires no additional empirical parameters, making it a practical tool for characterizing unconfined aquifer properties.