The influence of seasonal climatic variability on shallow infiltration at Yucca Mountain
- Geological Survey, Mercury, NV (United States)
Yucca Mountain, Nevada, is currently being evaluated as a potential location for an underground high-level nuclear waste repository, and the characterization of natural infiltration at this arid site is required. To analyze infiltration and the redistribution of moisture in alluvial deposits at Yucca Mountain, water content profiles at a 13.5 meter deep borehole were measured at monthly intervals using a neutron moisture probe. Measured profiles for the period 1/11/90 to 10/07/92 indicated increases in water content to a maximum depth of 1.8 meters in response to winter-season precipitation events, followed by a more gradual drying of the wetted zone due to evapotranspiration and possible downward percolation. Below a depth of 1.8 meters, a gradual drying trend was indicated for the entire measurement period by a small but consistent decrease in water contents throughout the profile. To analyze the influence of a longer climatic record on the water content profile, a one dimensional numerical model of unsaturated flow was calibrated to the measured water content profiles using measured daily precipitation and estimated potential evapotranspiration. The use of a 7.1 meter deep root-zone and a moisture dependent evapotranspiration function in the model provided a close agreement between the simulated and measured profiles for the 990 day calibration period. A 15 year record of daily precipitation and air temperatures at Desert Rock Airport, approximately 30 miles southeast of the study site, was used to provide a hypothetical climatic record for Yucca Mountains. Multiplying daily precipitation by factors of 0.5, 1.0, 1.5, 2.0, and 2.5 provided variations of the hypothetical record for investigating the influence of climatic variability on the moisture profile. Results indicated a maximum penetration of the simulated wetting front to a depth of 6.9 meters in response to the occurrence of two consecutive anomalously wet years.
- Research Organization:
- American Nuclear Society, La Grange Park, IL (United States); American Society of Civil Engineers, New York, NY (United States)
- OSTI ID:
- 60851
- Report Number(s):
- CONF-930408--Vol.1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
54 ENVIRONMENTAL SCIENCES
ALLUVIAL DEPOSITS
ATMOSPHERIC PRECIPITATIONS
CLIMATES
EVAPORATION
HIGH-LEVEL RADIOACTIVE WASTES
HYDROLOGY
MATHEMATICAL MODELS
MOISTURE
NEUTRON PROBES
PROBABILISTIC ESTIMATION
RADIOACTIVE WASTE DISPOSAL
RAIN
SEASONAL VARIATIONS
SITE CHARACTERIZATION
UNDERGROUND DISPOSAL
YUCCA MOUNTAIN
Yucca Mountain Project