Characterization of Hydraulic Properties of the Memphis Aquifer by Conducting Pumping Tests in Active Well Fields in Shelby County, Tennessee

Abstract

Limited availability of field measurements for aquifer parameters commonly leads to nonuniqueness of numerical model solutions. Six pumping tests were conducted in five municipal well fields within Shelby County following the procedure described in the ASTM D4050-14 and using an additional qualitative matrix framework to achieve greater reliability. Drawdown data of the pumping tests were analyzed using AQTESOLV, which allowed for partial penetration of well screens and interference from neighboring production wells. The values of transmissivity have a combined range of 600–3,100 m2/day, which is 2–4 times less than published measures that used less robust data analysis and questionable or poorly documented methods. The range of storativity was 0.0005–0.002, and again, the resulting values have greater reliability than prior investigations. Robust quality assessment in the present methodology through assignment of a scoring decision matrix provides greater trust in the measurements. With a score at or above 10 considered optimal, the methodology and test environment resulted in an average score of 8.7, a vast improvement from prior investigations that together averaged 4.1. The calculated parameter values are an improvement on historical values, constraining the two critical groundwater hydraulic terms that should reduce modeling nonuniqueness of numerical modeling solutions that should lead to improved evaluation of local groundwater resources and environmental impacts.