Hydrology of Yucca Mountain and vicinity, Nevada-California: investigative results through mid-1983
Yucca Mountain is located within the Alkali Flat-Furnace Creek Ranch ground-water subbasin, which is tributary to the Death Valley ground-water basin. Under present climatic conditions, most ground-water recharge occurs at Pahute Mesa, at mountain ranges farther north, and perhaps at Timber Mountain. Smaller amounts of recharge probably occur beneath larger washes, such as Fortymile Canyon-Fortymile Wash. Two major ground-water discharge areas occur within the subbasin: Alkali Flat (Franklin Lake), where discharge occurs almost entirely by evapotranspiration; and Furnace Creek Ranch area in Death Valley, where discharge results from numerous small springs. Beneath Yucca Mountain, depth to ground water ranges from about 460 to about 700 m. Perched water may be present, but the data are equivocal. Few data are available on the occurrence and movement of water in the unsaturated zone. Recharge at Yucca Mountain is probably less than 5 mm/yr, and perhaps much less. Within the saturated zone, water moves generally southeast or south, primarily through fractures. The hydraulic gradient is very low on the eastern (downgradient) side of Yucca Mountain. The gradient increases west and north; the increase in gradient is evidence of an area of low permeability. Data on locations of permeable fractures in drill holes are not sufficient for definition of hydrostratigraphic units. However, observations of fracture frequency, as related to lithology, and data obtained from similar rocks beneath Pahute Mesa support the hypothesis that densely welded tuffs fracture more readily than nonwelded and bedded tuffs do; therefore, these tuffs are likely to be more permeable. Proximity to faults, stress state, and the healing of fractures by mineral deposition affect fracture permeability of a mass of rock and complicate the conceptual model of water movement beneath Yucca Mountain. Data are not sufficient to predict accurately rates of water movement and travel times.
- Research Organization:
- Geological Survey, Denver, CO (United States)
- DOE Contract Number:
- AI08-78ET44802
- OSTI ID:
- 59690
- Report Number(s):
- USGS/WRI--84-4267; ON: DE85005673
- Country of Publication:
- United States
- Language:
- English
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