FACTORS INFLUENCING RECHARGE TO THE MEMPHIS AQUIFER IN AN URBAN WATERSHED

The Memphis aquifer is a valuable groundwater resource for west Tennessee. To ensure sustainability of this resource, aquifer recharge processes need to be fully understood and quantified. Previous studies of recharge to the Memphis aquifer in rural and urban areas show recharge occurs more efficiently where precipitation or runoff infiltrates into the Memphis Sand or sandy soil exposed at the surface. Hydrologic and meteorological data collected and analyzed over a three-year period are used to determine recharge rates by water balance in the outcrop belt of the Memphis Sand in the Sandy Creek watershed in Jackson, Tennessee. These data help determine the sensitivity of recharge to meteorological and runoff measurements in the watershed and are used to develop a predictive relationship. Sandy Creek is an ephemeral urban stream incised into the Memphis Sand with water primarily present during or immediately after precipitation events. Previous studies indicate annual recharge rates of as much as 300 to 900 mm/yr in the Sandy Creek watershed. Preliminary results indicate recharge to the Memphis aquifer based on an October to September water year ranges from 430 mm/yr in 2016-17 to 810 mm/yr in 2017-18. Preliminary investigation shows correlations between recharge and precipitation (total and intensity), evapotranspiration, stream discharge, and soil moisture content. Relationships between the variables will be evaluated on a monthly and yearly basis using the available data. A multiple regression model will be fit to the data to estimate groundwater recharge in areas with similar land use, surface soil exposure, and climate conditions.