Finite-element simulation of ground-water flow in the vicinity of Yucca Mountain, Nevada-California

A finite-element model of the ground-water flow system in the vicinity of Yucca Mountain at the Nevada Test Site was developed using parameter-estimation techniques. The model simulated steady-state ground-water flow occurring in tuffaceous, volcanic, and carbonate rocks, and alluvial aquifers. Hydraulic gradients in the modeled area range from 0.00001 for carbonate aquifers to 0.19 for barriers in tuffaceous rocks. Three model parameters were used in estimating transmissivities in six zones. Simulated hydraulic-head values range from about 1200 meters near Timber Mountain to about 300 meters near Furnace Creek Ranch. Model residuals for simulated versus measured hydraulic heads range from -28.6 to 21.4 meters; most are less than +-7 meters, indicating an acceptable representation of the hydrologic system by the model. Sensitivity analyses of the model's flux boundary-condition variables were performed to assess the effect of varying boundary fluxes on the calculation of estimated model transmissivities. Varying the flux variables representing discharge at Franklin Lake and Furnace Creek Ranch has greater effect than varying other flux variables. 60 refs., 6 figs., 5 tabs