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C. J. Fridrich

Publications and source records attributed to C. J. Fridrich.

12 recordsLinked to original sources
USGS2012

Geologic map of the southern Funeral Mountains including nearby groundwater discharge sites in Death Valley National Park, California and Nevada

This 1:50,000-scale geologic map covers the southern part of the Funeral Mountains, and adjoining parts of four structural basins—Furnace Creek, Amargosa Valley, Opera House, and central Death Valley—in California and Nevada. It extends over three full 7.5-minute quadrangles, and parts of eleven others—an area of about 1,000 square kilometers (km2). The boundaries of this map were drawn to include all of the known proximal hydrogeologic features that may affect the flow of groundwater that discharges from springs of the Furnace Creek basin, in the west-central part of the map. These springs provide the main potable water supply for Death Valley National Park. Major hydrogeologic features shown on this map include: (1) springs of the Furnace Creek basin, (2) a large Pleistocene groundwater discharge mound in the northeastern part of the map, (3) the exposed extent of limestones and dolomites that constitute the Paleozoic carbonate aquifer, and (4) the exposed extent of the alluvial conglomerates that constitute the Funeral Formation aquifer.

California;Nevada↗
USGS2005

Numerical modeling of perched water under Yucca Mountain, Nevada

The presence of perched water near the potential high-level nuclear waste repository area at Yucca Mountain, Nevada, has important implications for waste isolation. Perched water occurs because of sharp contrasts in rock properties, in particular between the strongly fractured repository host rock (the Topopah Spring welded tuff) and the immediately underlying vitrophyric (glassy) subunit, in which fractures are sealed by clays that were formed by alteration of the volcanic glass. The vitrophyre acts as a vertical barrier to unsaturated flow throughout much of the potential repository area. Geochemical analyses (Yang et al. 1996) indicate that perched water is relatively young, perhaps younger than 10,000 years. Given the low permeability of the rock matrix, fractures and perhaps fault zones must play a crucial role in unsaturated flow. The geologic setting of the major perched water bodies under Yucca Mountain suggests that faults commonly form barriers to lateral flow at the level of the repository horizon, but may also form important pathways for vertical infiltration from the repository horizon down to the water table. Using the numerical code UNSAT2, two factors believed to influence the perched water system at Yucca Mountain, climate and fault-zone permeability, are explored. The two-dimensional model predicts that the volume of water held within the perched water system may greatly increase under wetter climatic conditions, and that perched water bodies may drain to the water table along fault zones. Modeling results also show fault flow to be significantly attenuated in the Paintbrush Tuff non-welded hydrogeologic unit.

Groundwater↗
USGS2003

A methodology for probabilistic fault displacement hazard analysis (PFDHA)

We present a methodology for conducting a site-specific probabilistic analysis of fault displacement hazard. Two approaches are outlined. The first relates the occurrence of fault displacement at or near the ground surface to the occurrence of earthquakes in the same manner as is done in a standard probabilistic seismic hazard analysis (PSHA) for ground shaking. The methodology for this approach is taken directly from PSHA methodology with the ground-motion attenuation function replaced by a fault displacement attenuation function. In the second approach, the rate of displacement events and the distribution for fault displacement are derived directly from the characteristics of the faults or geologic features at the site of interest. The methodology for probabilistic fault displacement hazard analysis (PFDHA) was developed for a normal faulting environment and the probability distributions we present may have general application in similar tectonic regions. In addition, the general methodology is applicable to any region and we indicate the type of data needed to apply the methodology elsewhere.

Earthquake Spectra↗
USGS2002

Ground-water discharge determined from measurements of evapotranspiration, other available hydrologic components, and shallow water-level changes, Oasis Valley, Nye County, Nevada

Oasis Valley is an area of natural ground-water discharge within the Death Valley regional ground-water flow system of southern Nevada and adjacent California. Ground water discharging at Oasis Valley is replenished from inflow derived from an extensive recharge area that includes the northwestern part of the Nevada Test Site (NTS). Because nuclear testing has introduced radionuclides into the subsurface of the NTS, the U.S. Department of Energy currently is investigating the potential transport of these radionuclides by ground water flow. To better evaluate any potential risk associated with these test-generated contaminants, a number of studies were undertaken to accurately quantify discharge from areas downgradient in the regional ground-water flow system from the NTS. This report refines the estimate of ground-water discharge from Oasis Valley. Ground-water discharge from Oasis Valley was estimated by quantifying evapotranspiration (ET), estimating subsurface outflow, and compiling ground-water withdrawal data. ET was quantified by identifying areas of ongoing ground-water ET, delineating areas of ET defined on the basis of similarities in vegetation and soil-moisture conditions, and computing ET rates for each of the delineated areas. A classification technique using spectral-reflectance characteristics determined from satellite imagery acquired in 1992 identified eight unique areas of ground-water ET. These areas encompass about 3,426 acres of sparsely to densely vegetated grassland, shrubland, wetland, and open water. Annual ET rates in Oasis Valley were computed with energy-budget methods using micrometeorological data collected at five sites. ET rates range from 0.6 foot per year in a sparse, dry saltgrass environment to 3.1 feet per year in dense meadow vegetation. Mean annual ET from Oasis Valley is estimated to be about 7,800 acre-feet. Mean annual ground-water discharge by ET from Oasis Valley, determined by removing the annual local precipitation component of 0.5 foot, is estimated to be about 6,000 acre-feet. Annual subsurface outflow from Oasis Valley into the Amargosa Desert is estimated to be between 30 and 130 acre-feet. Estimates of total annual ground-water withdrawal from Oasis Valley by municipal and non-municipal users in 1996 and 1999 are 440 acre-feet and 210 acre-feet, respectively. Based on these values, natural annual ground-water discharge from Oasis Valley is about 6,100 acre-feet. Total annual discharge was 6,500 acre-ft in 1996 and 6,300 acre-ft in 1999. This quantity of natural ground-water discharge from Oasis Valley exceeds the previous estimate made in 1962 by a factor of about 2.5. Water levels were measured in Oasis Valley to gain additional insight into the ET process. In shallow wells, water levels showed annual fluctuations as large as 7 feet and daily fluctuations as large as 0.2 foot. These fluctuations may be attributed to water loss associated with evapotranspiration. In shallow wells affected by ET, annual minimum depths to water generally occurred in winter or early spring shortly after daily ET reached minimum rates. Annual maximum depths to water generally occurred in late summer or fall shortly after daily ET reached maximum rates. The magnitude of daily water-level fluctuations generally increased as ET increased and decreased as depth to water increased.

Nevada↗
USGS1994

Hydrogeologic analysis of the saturated-zone ground-water system, under Yucca Mountain, Nevada

The configuration of the southward-sloping water table under Yucca Mountain is dominated by an abrupt decline of 300 m over a distance of less than 2 km. This northeast-striking zone of large hydraulic gradient (of 0.15 or more) separates an area of moderate gradient (of about 0.015) to the north from an area of very small gradient (0.0001) to the south. The position of the large gradient does not correlate well with any evident geologic feature in the upper 0.5 km of the mountain, but we suggest that buried geologic features are present that can explain all the geohydrologic observations. The three areas of differing hydraulic gradient under Yucca Mountain are parts of hydrogeologic domains that extend more than 70 km to the northeast. On a regional basis, the moderate and very small gradients generally correspond to areas underlain by exceptionally thick Tertiary volcanic sections and a highly transmissive Paleozoic carbonate aquifer, respectively. The regional large gradient and water-table decline are spatially associated with a contact in the Paleozoic rocks between clastic rocks and carbonates. This contact marks a large abrupt drop in the effective base of the hydrologic system because it is the upgradient boundary of the deep carbonate aquifer, which has a thickness of 5 km. An aeromagnetic high follows the regional-scale domain of large gradient under northern Yucca Mountain from outcrops of a magnetite-bearing clastic confining unit to the east, indicating that the regional correlation of the steep water-table decline with the upgradient boundary of the deep carbonate aquifer may extend to Yucca Mountain. Five additional features may be related to an explanation for the large hydraulic gradient: (1) anomalously low heat flow has been measured deep in the volcanic section south of the water-table decline, suggesting underflow of cool water in the deep carbonate aquifer; (2) the lower tuff sequence, of 0.5–1 km in thickness, which underlies most of Yucca Mountain, is largely replaced in the volcanic section by lavas in the area of the large gradient; (3) an analysis of the hydrogeology of the tuff section under Yucca Mountain indicates that transmissivity in the tuffs increases to the south; (4) a northeast-trending gravity low is present immediately south of the water-table decline; (5) units in the lower part of the volcanic section are 50–100% thicker in the area of the gravity low than to the north and south. The abrupt stratigraphic thickening into the area of the gravity low indicates that the low represents a buried graben with its northern bounding fault centered beneath the abrupt water-table decline. These geologic features of the zone of large gradient under Yucca Mountain suggest two possible hydrogeologic models. First, the northern bounding fault of the buried graben may provide a highly permeable pathway (a drain) through the brittle lavas in the lower part of the volcanic section under northern Yucca Mountain. The drain would allow flow from the tuff aquifer north of the decline to be captured by the deep carbonate aquifer, resulting in the heat-flow low, the abrupt water-table decline, and the transition to a very small hydraulic gradient. Alternatively, the northern bounding fault of the buried graben may be the effective northern limit of the tuff aquifer under Yucca Mountain because the permeability in the tuffs north of the fault may have been diminished by hydrothermal alteration. In this second model, the large gradient marks the point where the small southward flow of water through the altered volcanic rocks to the north abruptly drops into the tuff aquifer. In either case, heads in the tuff aquifer in the area of very small gradient may be regulated partly by upward flow from the deep carbonate aquifer. This upward flow under southern Yucca Mountain is indicated by linear thermal highs along fault zones, by ground-water isotopic data suggesting inmixing of waters from the deep carbonate aquifer into the tuff aquifer, and by the upward hydraulic gradient found in a drill hole that penetrates the deep carbonate aquifer under southern Yucca Mountain.

Journal of Hydrology↗