Analyzing flow patterns in unsaturated fractured rock of Yucca Mountain using an integrated modeling approach

Analyzing Flow Patterns in Unsaturated Fractured Rock of Yucca Mountain Using an Integrated Modeling Approach Yu-Shu Wu, Guoping Lu, Keni Zhang, L. Pan, and G. S. Bodvarsson Abstract This paper presents a series of modeling investigations to characterize percolation patterns in the unsaturated zone of Yucca Mountain, Nevada, a proposed underground repository site for storing high-level radioactive waste. The investigations are conducted using a modeling approach that integrates a wide variety of moisture, pneumatic, thermal, and isotopic geochemical field data into a comprehensive three-dimensional numerical model through model calibration. This integrated modeling approach, based on a dual- continuum formulation, takes into account the coupled processes of fluid and heat flow and chemical isotopic transport in Yucca Mountain’s highly heterogeneous, unsaturated fractured tuffs. In particular, the model results are examined against different types of field-measured data and used to evaluate different hydrogeological conceptual models and their effects on flow patterns in the unsaturated zone. The objective of this work to provide understanding of percolation patterns and flow behavior through the unsaturated zone, which is a crucial issue in assessing repository performance. Index Terms: 1982 Hydrology: Groundwater Hydrology; 1983 Hydrology: Groundwater Transport; 1866 Hydrology: Unsaturated Zone. Key Words: unsaturated zone, fractured rock, Yucca Mountain, dual-continuum model, Richards’ equation, perched water.