Regional groundwater modeling of the Yucca Mountain site using analytic elements

Two of the complicating factors in modeling the regional groundwater flow at Yucca Mountain are the large distance to hydrogeologic boundaries and the large thickness of the aquifer; the hydrogeologic boundaries are up to 500 km away from Yucca Mountain, and the aquifer is up to 5000 m thick. The distant hydrogeologic boundaries may be taken into account explicitly by application of the analytic element method, which is applied to a model of this size for the first time in this study. The analytic element method makes it possible to include distant hydrogeologic boundaries and at the same time allows for local detail without the excessive computational effort that would be required with the finite difference method. Regional flow in the aquifer is modeled with a single layer, based on a theoretical argument and supported by the model results. The match between simulated and measured heads is similar to that of previous finite difference models of parts of the region; these previous studies consist of multiple layers and include inferred boundary conditions (head or flux specified) along most of the boundary of the domain. (C) 1999 Elsevier Science B.V.