Simultaneous water and solute movement through an unsaturated soil following an increase in recharge

Abstract

Playa lakes have been promoted as potential point sources of recharge to the High Plains aquifer, but information about recharge rates is only available for the Southern High Plains, where soils and substrate differ significantly from the Central High Plains. The goal of this study is to determine the degree to which functioning playas contribute to recharge of the aquifer in the Central High Plains. This is accomplished through a multifaceted study across a single 34–43 day-long playa hydroperiod, combining physical and geochemical evidence to measure fluid flux through the playa and geochemical evidence of fluid flux through the nearby interplaya. The hydroperiod resulted in increased matric potential and decreases in chloride and other anion concentrations in the vadose zone beneath the playa, and increases in groundwater levels downgradient, likely indicating recharge to the aquifer over the course of the short event. Anion concentrations are significantly higher in the interplaya compared with the playa, while fluid flux estimates are significantly higher beneath the playa. The fluid fluxes determined in this study are consistent with estimates from elsewhere in the High Plains region. The combination of physical and geochemical data decreased the uncertainty and improved the overall conclusion that recharge rates are higher beneath the playa than the interplaya, providing evidence that playas in the Central High Plains function similarly to those in the Southern High Plains.