| This thesis tests a series of potential future climate scenarios and associated environmental conditions that could result in the reversal of the present upward hydraulic gradient in the vadose zone at the Area 5 Radioactive Waste Management Site (RWMS) by implementing a one-dimensional model developed using the HYDRUS 1-D numerical modeling package. The research is divided into two phases. Phase I simulates the system from the Pleistocene to Holocene transition (approximately 13,000 years ago) to the present and is tested by independently varying precipitation, evaporation and transpiration rates. The results provide initial conditions for subsequent modeling under Phase II, which considers potential future flow conditions under a series of eight possible bioclimatic scenarios analogous to potential future climates for the next +1,000 years. Results indicate that the net upward hydraulic gradient is reversed under four of the future (Phase II) cases considered where vegetation does not effectively remove available soil moisture. This scenario can occur in periods of (1) warmer temperatures, higher precipitation rates and expanded vegetation cover, (2) warmer temperatures, lower precipitation rates and reduced vegetation cover, and (3) cooler temperatures, higher precipitation rates and expanded vegetation cover. |
