A Conceptual Model of the Death Valley Ground Water Flow System, Nevada and California PDF Download

Author: Pal Consultants, Inc
Publisher:
ISBN:
Category : Death Valley National Park (Calif. and Nev.)
Languages : en
Pages : 200

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Author:
Publisher:
ISBN:
Category : Death Valley National Park (Calif. and Nev.)
Languages : en
Pages : 182

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Author:
Publisher:
ISBN:
Category : Government publications
Languages : en
Pages : 136

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Author: Richard K. Waddell
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 90

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 5

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In the early 1990's, two numerical models of the Death Valley regional ground-water flow system were developed by the U.S. Department of Energy. In general, the two models were based on the same basic hydrogeologic data set. In 1998, the U.S. Department of Energy requested that the U.S. Geological Survey develop and maintain a ground-water flow model of the Death Valley region in support of U.S. Department of Energy programs at the Nevada Test Site. The purpose of developing this ''second-generation'' regional model was to enhance the knowledge and understanding of the ground-water flow system as new information and tools are developed. The U.S. Geological Survey also was encouraged by the U.S. Department of Energy to cooperate to the fullest extent with other Federal, State, and local entities in the region to take advantage of the benefits of their knowledge and expertise. The short-term objective of the Death Valley regional ground-water flow system project was to develop a steady-stat e representation of the predevelopment conditions of the ground-water flow system utilizing the two geologic interpretations used to develop the previous numerical models. The long-term objective of this project was to construct and calibrate a transient model that simulates the ground-water conditions of the study area over the historical record that utilizes a newly interpreted hydrogeologic conceptual model. This report describes the result of the predevelopment steady-state model construction and calibration.

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Category :
Languages : en
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A numerical ground-water flow model is being constructed for the Death Valley regional ground-water system, an area that encompasses approximately 80,000 km2 in southern Nevada and southeastern California. Effective construction and calibration of the regional-scale steady-state flow model, developed using MODFLOW-2000, is dependent upon integration of hydrogeologic data and parameter-estimation techniques. A three-dimensional hydrogeologic-framework model of the region was initially constructed to provide a conceptual model of the geometry, composition, and hydraulic properties of the materials that control the regional ground-water flow system. This framework was resampled at the scale of the flow model to define the hydrogeologic units present in each of the 15 flow-model layers. In addition, there are non-traditional types of geologic data in the hydrogeologic-framework model that are used during flow-model calibration. For each hydrogeologic unit, the spatial distribution of geologic features important to the hydrologic system is defined. The volumetric cells can be populated by various hydrogeologic data such as the hydrogeologic unit, lithology, hydraulic conductivity, faulting, tectonic features, stratigraphic or lithologic facies, porosity, and derivative data calculated from these attributes. The approach for using this arsenal of geologic data is dependent on utilizing parameter-estimation techniques available within MODFLOW-2000. The principle of parsimony is used throughout the flow-modeling process so that a simple conceptual model is methodically made more complex. Initially, the most basic conceptual model that could reasonably define the flow system was constructed and geologic units were grouped into four major hydrogeologic units. Only major geologic structures were included; there was little structural or stratigraphic differentiation, and a minimum number of parameters were used. As the calibration process progresses, additional complexity is added to the flow model. Evaluation of the flow model is based on analysis of several MODFLOW-2000 functions such as composite scaled sensitivity, weighted and unweighted hydraulic-head and flow residuals, comparison of parameter estimates with reasonable values based on previous studies, and parameter correlations. These functions provide information on whether the available hydraulic-head and ground-water discharge data are likely to be sufficient to estimate parameter values and to subdivide parameters into more detailed units. If sufficient data are available then a parameter can be subdivided into several parameters that represent specific distinguishing hydrogeologic features. For example, in the Death Valley region the lower carbonate aquifer is widely distributed and although regionally uniform, areas with unique hydrologic characteristics exist. Although the lower carbonate aquifer was initially considered one hydrogeologic unit with one set of hydrologic properties, it has been progressively subdivided into different structural and stratigraphic regions with unique hydrologic properties. The best flow model consists of the fewest number of parameters that can adequately describe the flow system and meet the modeling objectives.

Author:
Publisher:
ISBN:
Category : Groundwater flow
Languages : en
Pages : 144

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Author:
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ISBN:
Category :
Languages : en
Pages :

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A three-dimensional ground-water flow model has been developed to evaluate the Death Valley regional flow system, which includes ground water beneath the Nevada Test Site. Estimates of spatially distributed net infiltration and recharge are needed to define upper boundary conditions. This study presents a preliminary application of a conceptual and numerical model of net infiltration. The model was developed in studies at Yucca Mountain, Nevada, which is located in the approximate center of the Death Valley ground-water flow system. The conceptual model describes the effects of precipitation, runoff, evapotranspiration, and redistribution of water in the shallow unsaturated zone on predicted rates of net infiltration; precipitation and soil depth are the two most significant variables. The conceptual model was tested using a preliminary numerical model based on energy- and water-balance calculations. Daily precipitation for 1980 through 1995, averaging 202 millimeters per year over the 39,556 square kilometers area of the ground-water flow model, was input to the numerical model to simulate net infiltration ranging from zero for a soil thickness greater than 6 meters to over 350 millimeters per year for thin soils at high elevations in the Spring Mountains overlying permeable bedrock. Estimated average net infiltration over the entire ground-water flow model domain is 7.8 millimeters per year. To evaluate the application of the net-infiltration model developed on a local scale at Yucca Mountain, to net-infiltration estimates representing the magnitude and distribution of recharge on a regional scale, the net-infiltration results were compared with recharge estimates obtained using empirical methods. Comparison of model results with previous estimates of basinwide recharge suggests that the net-infiltration estimates obtained using this model may overestimate recharge because of uncertainty in modeled precipitation, bedrock permeability, and soil properties for locations such as the Spring Mountains. Although this model is preliminary and uncalibrated, it provides a first approximation of the spatial distribution of net infiltration for the Death Valley region under current climatic conditions.

Author:
Publisher: DIANE Publishing
ISBN: 1428917810
Category :
Languages : en
Pages : 94

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Author: Wayne R. Belcher
Publisher:
ISBN: 9781411329133
Category : Groundwater flow
Languages : en
Pages :

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