USGS


Preliminary Estimates of Spatially Distributed Net Infiltration and Recharge for the Death Valley Region, Nevada—California

By Joseph A. Hevesi, Alan L. Flint, and Lorraine E. Flint

 

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 02-4010

Sacramento, California 2001


Prepared in cooperation with the

NEVADA OPERATIONS OFFICE, U.S. DEPARTMENT OF ENERGY,
under Interagency Agreement DE-AI08-96NV11967




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Abstract

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.

Contents

Abstract

Introduction

Study Area Description

Geographic Setting

Climate

Hydrogeology

Surface Water

Ground Water

Soils

Vegetation

Previous Work

Acknowledgments

Conceptual Model of Net Infiltration for the Death Valley Region

Processes Controlling Net Infiltration

Development of a Conceptual Model of Net Infiltration

Precipitation

Evapotranspiration

Surface Water and Infiltration

Shallow Infiltration

Surface Water (run-on/runoff)

Redistribution and Net Infiltration

Processes at the Soil-Bedrock Interface

Estimation of Net Infiltration

Overview of Preliminary Net Infiltration Model (INFIL)

Model Grid

Model Inputs

Precipitation

Spatially Distributed Basin Properties

Soils

Rocks

Model Calculations

Energy Balance Calculations

Solar Radiation

Air Temperature

Calculation of Evapotranspiration

Calculation of Net Infiltration Using a Root-Zone Water Balance Model

Overview of the Root-Zone Water Balance

Daily Water-Balance Calculations

Soil and Bedrock Properties Used to Calculate Net Infiltration

Assumptions and Model Limitations

Model Results

Description of Preliminary Net Infiltration Model Results

Comparison of Preliminary Net Infiltration Model Results with Estimates of Spatially Distributed Recharge

Comparison of Preliminary Net Infiltration Model Results with Previous Basinwide Estimates of Recharge

Summary

References Cited



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Water Resources of California


U.S. Department of the Interior, U.S. Geological Survey
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