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J. R. Harrill

Publications and source records attributed to J. R. Harrill.

11 recordsLinked to original sources
USGS2010

Death Valley regional groundwater flow system, Nevada and California: Hydrogeologic framework and transient groundwater flow model

A numerical three-dimensional (3D) transient groundwater flow model of the Death Valley region was developed by the U.S. Geological Survey for the U.S. Department of Energy programs at the Nevada Test Site and at Yucca Mountain, Nevada. Decades of study of aspects of the groundwater flow system and previous less extensive groundwater flow models were incorporated and reevaluated together with new data to provide greater detail for the complex, digital model. A 3D digital hydrogeologic framework model (HFM) was developed from digital elevation models, geologic maps, borehole information, geologic and hydrogeologic cross sections, and other 3D models to represent the geometry of the hydrogeologic units (HGUs). Structural features, such as faults and fractures, that affect groundwater flow also were added. The HFM represents Precambrian and Paleozoic crystalline and sedimentary rocks, Mesozoic sedimentary rocks, Mesozoic to Cenozoic intrusive rocks, Cenozoic volcanic tuffs and lavas, and late Cenozoic sedimentary deposits of the Death Valley regional groundwater flow system (DVRFS) region in 27 HGUs. Information from a series of investigations was compiled to conceptualize and quantify hydrologic components of the groundwater flow system within the DVRFS model domain and to provide hydraulic-property and head-observation data used in the calibration of the transient-flow model. These studies reevaluated natural groundwater discharge occurring through evapotranspiration (ET) and spring flow; the history of groundwater pumping from 1913 through 1998; groundwater recharge simulated as net infiltration; model boundary inflows and outflows based on regional hydraulic gradients and water budgets of surrounding areas; hydraulic conductivity and its relation to depth; and water levels appropriate for regional simulation of prepumped and pumped conditions within the DVRFS model domain. Simulation results appropriate for the regional extent and scale of the model were provided by acquiring additional data, by reevaluating existing data using current technology and concepts, and by refining earlier interpretations to reflect the current understanding of the regional groundwater flow system. Groundwater flow in the Death Valley region is composed of several interconnected, complex groundwater flow systems. Groundwater flow occurs in three subregions in relatively shallow and localized flow paths that are superimposed on deeper, regional flow paths. Regional groundwater flow is predominantly through a thick Paleozoic carbonate rock sequence affected by complex geologic structures from regional faulting and fracturing that can enhance or impede flow. Spring flow and ET are the dominant natural groundwater discharge processes. Groundwater also is withdrawn for agricultural, commercial, and domestic uses. Groundwater flow in the DVRFS was simulated using MODFLOW-2000, the U.S. Geological Survey 3D finitedifference modular groundwater flow modeling code that incorporates a nonlinear least-squares regression technique to estimate aquifer parameters. The DVRFS model has 16 layers of defined thickness, a finite-difference grid consisting of 194 rows and 160 columns, and uniform cells 1,500 meters (m) on each side. Prepumping conditions (before 1913) were used as the initial conditions for the transient-state calibration. The model uses annual stress periods with discrete recharge and discharge components. Recharge occurs mostly from infiltration of precipitation and runoff on high mountain ranges and from a small amount of underflow from adjacent basins. Discharge occurs primarily through ET and spring discharge (both simulated as drains) and water withdrawal by pumping and, to a lesser amount, by underflow to adjacent basins simulated by constant-head boundaries. All parameter values estimated by the regression are reasonable and within the range of expected values. The simulated hydraulic heads of the final calibrated transient model generally fit observed heads reasonably well (residuals with absolute values less than 10 meters) with two exceptions: in most areas of nearly flat hydraulic gradient the fit is considered moderate (residuals with absolute values of 10 to 20 meters), and in areas of steep hydraulic gradient along the Eleana Range and western part of Yucca Flat, southern part of the Owlshead Mountains, southern part of the Bullfrog Hills, and the north-northwestern part of the model domain (residuals with absolute values greater than 20 meters). Groundwater discharge residuals are fairly random, with as many areas where simulated flows are less than observed flows as areas where simulated flows are greater. The highest unweighted groundwater discharge residuals occur at Death Valley, Sarcobatus Flat (northeastern area), Tecopa, and early observations at Manse Spring in Pahrump Valley. High weighted-discharge residuals were computed in Indian Springs Valley and parts of Death Valley. Most of these inaccuracies in head and discharge can be attributed to insufficient representation of the hydrogeology in the HFM and(or) discharge estimates, misrepresentation of water levels, and(or) model error associated with grid-cell size. The model represents the large and complex groundwater flow system of the Death Valley region at a greater degree of refinement and accuracy than has been possible previously. The representation of detail provided by the 3D digital hydrogeologic framework model and the numerical groundwater flow model enabled greater spatial accuracy in every model parameter. The lithostratigraphy and structural effects of the hydrogeologic framework; recharge estimates from simulated net infiltration; discharge estimates from ET, spring flow, and pumping; and boundary inflow and outflow estimates all were reevaluated, some additional data were collected, and accuracy was improved. Uncertainty in the results of the flow model simulations can be reduced by improving on the quality, interpretation, and representation of the water-level and discharge observations used to calibrate the model and improving on the representation of the HGU geometries, the spatial variability of HGU material properties, the flow model physical framework, and the hydrologic conditions.

California, Nevada↗
USGS1998

Aquifer systems in the Great Basin region of Nevada, Utah, and adjacent states; summary report

Findings of the Great Basin Regional Aquifer System Analysis (RASA) are summarized. The Great Basin RASA study encompasses an area of about 140,000 square miles. Regional hydrology and ground-water hydrology of the area are described. Five models of basin-fill aquifers, a ground-water flow model of the Fish Springs system, and a regional ground-water flow model of the carbonate-rock province (eastern Nevada and western Utah) are presented and discussed.

Professional Paper↗
USGS1995

Distribution of carbonate-rock aquifers and the potential for their development, southern Nevada and adjacent parts of California, Arizona, and Utah

In 1985, the State of Nevada entered into a cooperative effort with the U.S. Department of the Interior to study and test the State's carbonate- rock aquifers. The studies were focused on southern Nevada and were intended to address the following concerns: Where is water potentially available in the aquifers?; How much water potentially can bewithdrawn from aquifers?; and What effects might result from development of the aquifers? The studies included basic-data collection, geologic mapping, geophysical and geochemical analyses, well drilling, and aquifer testing. The studies showed that the carbonate rocks are continuous and extensive enough to form regional aquifer systems only beneath thecentral third of the region. About 130,000 acre-feet per year of ground water flows through all the aquifers in this corridor (carbonate and noncarbonate), and about 77,000 acre-feet per year discharges directly from the carbonate-rock aquifers at regional springs in southern Nevada or at discharge areas in Death Valley, California. A larger volume of water -as much as 6 million acre-feet in the upper 100 feet alone-is stored in the rocks. Once depleted, however, that resource would be replenished by natural processes only very slowly. Ultimately, long-term development of the carbonate-rock aquifers would result in depletion of stored water, or in the capture of water that otherwise would discharge from the aquifers of southern Nevada and vicinity, or both. In manyplaces, development might extract water from both carbonate-rock and basin-fill aquifers. Possible effects of developing the carbonate-rock aquifers include declining water levels, decreasing springflow rates, drying up of some streams, playas, and meadows, and changing water quality. Specific impacts would depend upon the magnitude and length of development and site-specific conditions around the areas where the water is withdrawn. Confidence in predictions of the potential effects ofdevelopment of the carbonate-rock aquifers will remain limited until observations become available that document changes as the aquifers respond locally to long-term pumping stresses. However, if staged development were undertaken together with adequate monitoring, effects of continued or increased development could be estimated with progressively higher degrees of confidence.

Water-Resources Investigations Report↗
USGS1995

Estimated natural ground-water recharge, discharge, and budget for the Dixie Valley area, west-central Nevada

The Dixie Valley area includes seven valleys in west-central Nevada (Dixie, Fairview, Stingaree, Cowkick, Eastgate, Pleasant, and Jersey Valleys; total, 2,380 square miles). Dixie Valley receives surface-water and ground-water flow from Stingaree, Cowkick, Eastgate, Pleasant, and Jersey Valleys and subsurface flow from Fairview Valley, which is a topographically closed basin. The relation between precipitation and altitude was re-evaluated for the Dixie Valley area using new data, and empirical estimates of recharge were revised accordingly. The revised estimate of total recharge is 23,000 acre-feet per Re-evaluation of ground-water discharge focused on Dixie Valley as the largest basin in the study area. Phreatophytic vegetation was mapped and partitioned into nine zones on the basis of species composition and foliage density. For woody phreatophytes, annual evapotranspiration rates of 0.7 cubic feet of water per cubic foot of foliage for greasewood and 1.1 cubic feet of water per cubic foot of foliage for rabbitbrush were adapted from lysimeter studies near Winnemucca, Nevada. These rates were multiplied by the foliage density of the respective phreatophytes in each zone to estimate a specific rate for that zone. Rates for salt-grass (0.5 to 0.8 foot per year) and the playa surface (0.1 to 0.3 foot per year) were based on a range of rates. used in other recent studies in western and central Nevada. These rates were multiplied by the areas of the zones to produce estimates of the annual volume of ground water discharged. The discharge estimated for Dixie Valley is between 17,000 and 28,000 acre-feet per year. The revised discharge estimate for the entire Dixie Valley area is between 20,000 and 31,000 acre-feet per year. The revised ground-water budget for the entire Dixie Valley study area has a total recharge of about 23,000 acre-feet per year. This is within the range of estimates of natural discharge--from 20,000 to 31,000 acre-feet per year. For Dixie Valley alone, the total recharge of about 8,900 acre-feet per year and the estimated subsurface inflow from tributary areas of about 11,000 acre-feet per year produce an estimated total inflow of about 20,000 acre-feet per year. This compares with the discharge estimate of 17,000 to 28,000 acre-feet per year.

Water-Resources Investigations Report↗
USGS1995

Simulated effects of proposed ground-water pumping in 17 basins of east-central and southern Nevada

The Las Vegas Valley Water District filed 146 applications in 1989 to pump about 180,800 acre- ft/yr in 17 basins for use in Las Vegas Valley. A previously constructed, two-layer computer model of the carbonate-rock province area was configured to simulate transient conditions and used to develop first approximations of the possible effects of these withdrawals. Simulations were made using the phased pumping schedule proposed by the water district. Ground-water-level declines of several hundred feet could ultimately develop in the basins scheduled to supply most of the pumped ground water. Simulated declines in the carbonate-rock aquifer were somewhat larger than simulated declines in the overlying basin-fill deposits. Decreases in simulated regional spring flow were shown in several cells including those representing the Muddy River Springs, Hiko-Crystal-Ash spring area, and the Ash Meadows spring area. Model simulations show flow decreases of about 11 percent, 14 percent, and 2 percent, respectively, at these springs after almost 100 years of pumping. Simulated evapotranspiration also decreased in many basins, with the largest decreases occurring in the basins where ground-water withdrawals were greatest. These basins include Railroad, Spring, and Snake Valleys. The largest decrease in simulated evapotranspiration occurred in Railroad Valley, 64 percent after almost 100 years of pumpage. Model-sensitivity tests indicate that long-term results were relatively insensitive to variations in values used for aquifer storage. The adequacy of the model to simulate the effects of this proposed pumping will remain untested until actual pumping stresses have been in place long enough to cause measurable effects within the system.

Water-Resources Investigations Report↗
USGS1993

Conceptual evaluation of regional ground-water flow in the carbonate-rock province of the Great Basin, Nevada, Utah, and adjacent states

The regional groundwater flow system in the carbonate rocks of Nevada and Utah is conceptualized as shallow systems superimposed on deeper systems, which transmit water primarily through carbonate rocks. A computer model was used to simulate the two systems. The regional model includes simplifying assumptions that are probably valid for parts of the province; however, the validity of each assumption is unknown for the province as a whole. Therefore, simulation results do not perfectly replicate actual groundwater flow; instead they provide a conceptual evaluation of regional groundwater flow. The model was calibrated by adjusting transmissivity and vertical leakance until simulated water levels and simulated discharge generally agreed with known water levels, mapped areas of discharge, and estimates of discharge. Simulated flow is about 1.5 million acre-ft/yr. Most groundwater flow is simulated in the upper model layer where about 45 shallow flow regions were identified. In the lower layer, 17 deep-flow subregions were identified and grouped into 5 large regions on the basis of water-flow patterns. Simulated flow in this layer is about 28 percent of the total inflow and about half is discharged as springflow. Interbasin flow to several large springs is through thick, continuous, permeable carbonate rocks; elsewhere deep consolidated rocks are not highly transmissive, suggesting that carbonate rocks are not highly permeable everywhere or are not present everywhere. (USGS)

Nevada, Utah↗
USGS1984

Maps showing ground-water units and withdrawal, Basin and Range Province, Nevada

This report on ground-water units and withdrawal in the Basin and Range province of Nevada (see index map) was prepared as part of a program of the U.S. Geological Survey to identify prospective regions for further study relative to isolation of high-level nuclear waste (Bedinger f Sargent, and Reed, 1984), utilizing program guidelines defined in Sargent and Bedinger (1984). Also included in this report are selected references on pertinent geologic and hydrologic studies of the region. Other map reports in this series contain detailed data on ground-water quality, surface distribution of selected rock types, tectonic conditions, areal geophysics, Pleistocene lakes and marshes, and mineral and energy resources.

Nevada↗
USGS1984

Maps showing ground-water levels, springs, and depth to water, Basin and Range Province, Nevada

This report on ground-water levels, springs and depth to ground water in the Basin and Range province of Nevada (see index map) was prepared as part of a program of the U.S. Geological Survey to identify prospective regions for further study relative to isolation of high-level nuclear waste (Bedinger, Sargent, and Reed, 1984), utilizing program guidelines defined in Sargent and Bedinger (1984). Also included in this report are selected references on pertinent geologic and hydrologic studies of the region. Other map reports in this series contain detailed data on ground-water quality, surface distribution of selected rock types, tectonic conditions, areal geophysics, Pleistocene lakes and marshes, and mineral and energy resources.

Nevada↗
USGS1975

Preliminary hydrogeologic appraisal of selected hydrothermal systems in northern and central Nevada

Several hydrothermal systems in northern and central Nevada were explored in a hydrogeologic reconnaissance. The systems studied comprise those at Stillwater and Soda Lakes-Upsal Hogback in the Carson Desert, Gerlach, Fly Ranch-Granite Range, and Double Hot Springs in the Black Rock Desert, Brady's Hot Springs, Leach Hot Springs in Grass Valley, Buffalo Valley Hot Springs, and Sulphur Hot Springs in Ruby Valley. The investigation focused on (1) delineating of areas of high heat flow associated with rising thermal ground water, (2) determining the nature of the discharge parts of the hydrothermal systems, (3) estimating heat discharge from the systems, (4) estimating water discharge from the systems, (5) obtaining rough estimates of, conductive heat flow outside areas of hydrothermal discharge, and (6) evaluating several investigative techniques that would yield the required information quickly and at relatively low cost. The most useful techniques were shallow test drilling to obtain geologic, hydraulic, and thermal data and hydrogeologic mapping of the discharge areas. The systems studied are in the north-central part of the Basin and Range province. Exposed volcanic rocks of latest Tertiary and Quaternary age are chiefly basaltic. Basaltic terranes are generally regarded as less favorable for geothermal resources than terranes that contain large volumes of young volcanic mocks of felsic to intermediate composition. Most of the known hydrothermal systems are associated with Basin and Range faults which are caused by crustal extension across the province. An area of high heat flow centered at Battle Mountain and possibly other areas of high heat flow may be related to crustal heat sources. However, some of the hydrothermal systems studied appear to be related to deep circulation of meteoric water in areas of 'normal' regional heat flow rather than to shallow-crustal heat sources. Discharge temperatures of thermal springs in the region range from slightly above mean annual air temperature (8?-12?C at most places) to boiling or slightly hotter. Geochemical data indicate that, in the major systems, subsurface temperatures at which thermal waters equilibrate with reservoir rocks range from 150? to more than 200?C. These data also indicate that the major systems are of the hot-water type rather than the vapor-dominated type. Depths of thermal-water circulation probably range from 2 to 6 kilometres in areas of 'normal' regional heat flow (~2 heatflow units) and from 1 to 3 kilometres in areas of high heat flow (~3-4 heat-flow units) such as near Battle Mountain. Most of the heat is discharged from the hydrothermal systems studied by (1) conduction through near-surface materials heated as a consequence of thermal-water convection, (2) convection as springflow, and (3) convection as steam discharge from spring pools, vents, fumaroles, and cracks. The mate of heat discharge by radiation from warm ground and by convection as lateral ground-water outflow is believed to be small in most systems and is not estimated. Estimates of net heat discharge from the systems studied range from about 0.8 x 106 calories per second at Buffalo Valley Hot Springs to about 14 x 106 calories per second at Stillwater. These estimates represent the approximate magnitude of the excess heat discharge from the thermal areas that results from the upward convection of hot water from deep sources. Water discharges from the hydrothermal systems by springflow, evapotranspiration, steam discharge, and lateral ground-water outflow. Estimated discharges range from about 0.2 x 106cubic metres per year from the Buffalo Valley Hot Springs system to about 3 x 106 cubic metres per year from the Stillwater system. In most of the hydrothermal systems studied and, by inference, in other similar systems in northern and central Nevada, the scale for potential .commercial development for production of electricity or for other uses may be constrained by the

Open-File Report↗