Abstract:Water supplies in Death Valley National Monument and vicinity are limited to groundwater sources, almost without exception. Most streams in the desert area flow only ephemerally, typically during flash floods. Ground water supports perennial flow over a few short reaches of some streams. There are several hundred freshwater springs and seeps in the monument, but only a small percentage of these, including most of the large springs, are in areas of present or projected intensive use by man. Most springs are in … Show more
“…This method has been applied to more than 200 basins in Nevada and in other western states. Controversy over the limitations and accuracy of this method has existed for some time (Watson et al, 1976;Miller, 1977). However, more recent studies by Dettinger (1989) and Avon and Durbin (1992) have indicated that the Maxey and Eakin approach yields recharge estimates that are generally in good agreement with independent estimates.…”
Significant uncertainty is associated with efforts to quantity recharge in arid regions such as southern Nevada. However, accurate estimates of groundwater recharge are necessary to understanding the long-term sustainability of groundwater resources and predictions of groundwater flow rates and directions. Currently, the most widely accepted method for estimating recharge in southern Nevada is the Maxey and Eakin method. This method has been applied to most basins within Nevada and has been independently verified as a reconnaissancelevel estimate of recharge through several studies. Recharge estimates derived from the Maxey and Eakin and other recharge methodologies ultimately based upon measures or estimates of groundwater discharge (outflow methods) should be augmented by a tracer-based aquiferresponse method. The objective of this study was to improve an existing aquifer-response method that was based on the chloride mass-balance approach. Improvements were designed to incorporate spatial variability within recharge areas (rather than recharge as a lumped parameter), develop a more defendable lower limit of recharge, and differentiate local recharge from recharge emanating as interbasin flux.Seventeen springs, located in the Sheep Range, Spring Mountains, and on the Nevada Test Site were sampled during the course of this study and their discharge was measured. The chloride and bromide concentrations of the springs were determined. Discharge and chloride concentrations from these springs were compared to estimates provided by previously published reports. A literature search yielded previously published estimates of chloride flux to the land surface.36 Cl/Cl ratios and discharge rates of the three largest springs in the Amargosa Springs discharge area were compiled from various sources. This information was utilized to determine an effective chloride concentration for recharging precipitation and its associated uncertainty via Monte Carlo simulations. Previously developed isohyetal maps were utilized to determine the mean and standard deviation of precipitation within the area. A digital elevation model was obtained to provide elevation information. A geologic model was obtained to provide the spatial distribution of alluvial formations. Both were used to define the lower limit of recharge. In addition, 40 boreholes located in alluvial sediments were drilled and sampled in an attempt to support the argument that the areal distribution of alluvial sediments can be used to define a zone of negligible recharge. The data were compiled in a geographic information system and used in a Monte Carlo analysis to determine recharge occurring within the study area. Results of the analysis yielded estimates of the mean and standard deviation of recharge occurring within the study area (28.168 x10 6 m 3 yr -1 and 7.008 x10 6 m 3 yr -1 , and 26.838 x10 6 m 3 yr -1 and 6.928 x10 6 m 3 yr -1 ) for two sets of simulations using alternate definitions of the lower limit of recharge. A sensitivity analysis determined the r...
“…This method has been applied to more than 200 basins in Nevada and in other western states. Controversy over the limitations and accuracy of this method has existed for some time (Watson et al, 1976;Miller, 1977). However, more recent studies by Dettinger (1989) and Avon and Durbin (1992) have indicated that the Maxey and Eakin approach yields recharge estimates that are generally in good agreement with independent estimates.…”
Significant uncertainty is associated with efforts to quantity recharge in arid regions such as southern Nevada. However, accurate estimates of groundwater recharge are necessary to understanding the long-term sustainability of groundwater resources and predictions of groundwater flow rates and directions. Currently, the most widely accepted method for estimating recharge in southern Nevada is the Maxey and Eakin method. This method has been applied to most basins within Nevada and has been independently verified as a reconnaissancelevel estimate of recharge through several studies. Recharge estimates derived from the Maxey and Eakin and other recharge methodologies ultimately based upon measures or estimates of groundwater discharge (outflow methods) should be augmented by a tracer-based aquiferresponse method. The objective of this study was to improve an existing aquifer-response method that was based on the chloride mass-balance approach. Improvements were designed to incorporate spatial variability within recharge areas (rather than recharge as a lumped parameter), develop a more defendable lower limit of recharge, and differentiate local recharge from recharge emanating as interbasin flux.Seventeen springs, located in the Sheep Range, Spring Mountains, and on the Nevada Test Site were sampled during the course of this study and their discharge was measured. The chloride and bromide concentrations of the springs were determined. Discharge and chloride concentrations from these springs were compared to estimates provided by previously published reports. A literature search yielded previously published estimates of chloride flux to the land surface.36 Cl/Cl ratios and discharge rates of the three largest springs in the Amargosa Springs discharge area were compiled from various sources. This information was utilized to determine an effective chloride concentration for recharging precipitation and its associated uncertainty via Monte Carlo simulations. Previously developed isohyetal maps were utilized to determine the mean and standard deviation of precipitation within the area. A digital elevation model was obtained to provide elevation information. A geologic model was obtained to provide the spatial distribution of alluvial formations. Both were used to define the lower limit of recharge. In addition, 40 boreholes located in alluvial sediments were drilled and sampled in an attempt to support the argument that the areal distribution of alluvial sediments can be used to define a zone of negligible recharge. The data were compiled in a geographic information system and used in a Monte Carlo analysis to determine recharge occurring within the study area. Results of the analysis yielded estimates of the mean and standard deviation of recharge occurring within the study area (28.168 x10 6 m 3 yr -1 and 7.008 x10 6 m 3 yr -1 , and 26.838 x10 6 m 3 yr -1 and 6.928 x10 6 m 3 yr -1 ) for two sets of simulations using alternate definitions of the lower limit of recharge. A sensitivity analysis determined the r...
“…The Grapevine Mountains are underlain by intensely folded and faulted sedimentary rocks of Paleozoic age. In the central to northern part of the range, the sedimentary rocks are capped by volcanic basalts of Tertiary age (Miller, 1977).…”
“…Throughout the study area, Precambrian igneous and metamorphic intrusive (basement) rocks form the cores of mountain ranges. These rocks are overlain by thick sections of Paleozoic sedimentary strata, Mesozoic and Cenozoic intrusive, extrusive, and clastic rock formations, and extensive accumulations of alluvial, colluvial, and eolian sediments (Miller, 1977;Bedinger and others, 1989). The ranges and intervening valleys in the study area are part of the complex horst-and-graben structural framework of the Basin and Range.…”
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