Keith J. Halford Tracie R. Jackson 2019 <p>The rate of groundwater flow past underground nuclear testing areas in Yucca Flat at the Nevada National Security Site, southern Nevada, was estimated using results from the <i>ER-6-1-2 main</i> multiple-well aquifer test (MWAT), done during February 5–July 23, 2004. Drawdowns in 13 observation wells were evaluated from pumping in well <i>ER-6-1-2 main</i> and used as observations in a regional groundwater-flow model to estimate the groundwater-flow rate. Flow from southern Yucca Flat regionally was constrained by detecting drawdown in <i>Tracer Well 3</i>, which is 33 miles south-southwest of pumping well <i>ER-6-1-2 main</i>. Predevelopment flow, the <i>ER-6-1-2 main</i> MWAT, and regional groundwater pumping were simulated in separate models that jointly informed estimates of transmissivity and specific-yield distributions. Predevelopment flow constrained groundwater-flow estimates from southern Yucca Flat because the steady-state model correctly simulated regional groundwater discharges in the Ash Meadows groundwater basin and the surrounding basins. Less than 600 acre-feet per year of groundwater moves from underground nuclear testing areas and flows south of well <i>ER-6-1-2 main</i> in southern Yucca Flat.</p> application/pdf 10.3133/sir20195038 en U.S. Geological Survey Estimation of groundwater flow through Yucca Flat based on a multiple-well aquifer test at well <em>ER-6–1–2 main</em>, Nevada National Security Site, southern Nevada reports