SEAWAT code used to couple MODFLOW and MT3DMS models, and supplemental data used to simulate groundwater flow and tritium transport from the HANDLEY underground nuclear test, Pahute Mesa, southern Nevada

Three-dimensional numerical models were used to determine the permeable pathways between the HANDLEY underground nuclear test and downgradient boreholes ER-20-12 and PM-3, Pahute Mesa, southern Nevada. The SEAWAT code was used to couple MODFLOW and MT3DMS models, where the coupled model simulated groundwater-flow and tritium migration from the HANDLEY test for 50 years, from the date of detonation of the HANDLEY test (March 26, 1970) to March 26, 2020. Recharge, hydraulic-conductivity, specific-storage, and effective-porosity distributions were estimated using parameter estimation (PEST) by minimizing a weighted composite, sum-of-squares objective function. Simulated water-level altitudes in 10 wells, vertical water-level differences [...]