Studies are currently underway to determine the suitability of Yucca Mountain
in Nevada as the nation's first high-level nuclear waste repository. Values of net
infiltration are required to determine pre-waste emplacement groundwater travel times
and the performance of the repository as a waste containment system. The objective of
this study was to develop a numerical model to perform water balance calculations and
predict rates of net infiltration for the site. The model included processes of
precipitation, runoff, evapotranspiration, infiltration, and redistribution of water within
a soil profile. The watershed was divided into 477 grid cells 75.7 x 75.7 m. The
elevation, slope, aspect, and hydrologic properties were assumed to be constant within
a grid cell but varied from one cell to the next Water balance calculations were
performed for each cell using a one-dimensional form of Richards equation. The
solution was obtained using the finite difference method with Newton-Raphson
iteration.
The model was calibrated using water content data obtained from neutron-moisture
meter measurements in boreholes located in Pagany Wash Watershed
Measurements were made in channel and terrace alluvium and in tuffs. Computer
simulations reproduced water content data for a major precipitation event that occurred
in 1984. Simulations verified the importance of antecedent soil water content in
controlling the occurrence of runoff. Sensitivity analysis indicated that the soil and
alluvium grain-size distributions, which are used to calculate unsaturated hydraulic
conductivity, can greatly affect predicted rates of water movement / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/38116 |
| Date | 24 July 1990 |
| Creators | Britch, Michael J. |
| Contributors | Istok, Jonathan D. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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