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WRIR 99-4079: Estimates of Ground-Water Discharge as Determined from Measurements of Evapotranspiration, Ash Meadows Area, Nye County, Nevada

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CONTENTS

Abstract
Introduction
Purpose and Scope
Acknowledgments
Location and Jurisdiction
General Description and Setting
General Hydrology
Ground-Water Discharge
Quantification of Evapotranspiration
Evapotranspiration Units
Spectral Classification
Accuracy Assessment
Evapotranspiration Rates
Energy Budget Method
Site Selection and Instrumentation Micrometeorological Data and Daily and Annual Evapotranspiration
Water-Table Fluctuations
Data Collection Network and Methods
Annual and Daily Fluctuations
Estimates of Annual Evapotranspiration and Ground-Water Discharge
Limitations of Methodology
Summary
References Cited
Supplemental Data

PLATES

1-2. Maps showing for Ash Meadows area, Nevada:

Plate 1. Distribution of evapotranspiration (ET) units and graphs of fluctuation in water level and daily ET

Plate 2. Location of shallow observation wells within evapotranspiration (ET) units and graphs of water-table fluctuation

FIGURES

1-3. Maps showing for Ash Meadows, Nevada:
  1. Other major areas of natural discharge within Death Valley ground-water flow system potentially influencing ground-water flow at Nevada Test Site
  2. Generalized geology
  3. Major hydrographic and physiographic features
4. Schematic of generalized cross section showing local hydrologic and geologic features controlling ground-water flow in Ash Meadows area, Nevada
5. Map showing color infrared composite generated from June 13, 1992, thematic mapper image, Ash Meadows area, Nevada 
6. Graphs showing spectral-response curves for land covers of different vegetation and soil conditions
7. Graphs showing spectral clusters and component spectral-response curves used in June and September 1992 image classifications for land covers of different vegetation and soil conditions equated with ground-water evapotranspiration in Ash Meadows area, Nevada
8. Schematic of instrumentation arrangements installed and used to measure micrometeorological data to determine evapotranspiration over land and water from Ash Meadows area, Nevada
9. Photographs showing typical instrument installations used to determine evapotranspiration over land and water from Ash Meadows area, Nevada
10-11.  Graphs showing for Carson Meadow ET site, September 1-5, 1996:
  10. Micrometeorological data collected
  11. Energy-budget fluxes and daily evapotranspiration calculated from meteorological data collected
12. Graphs showing calculated daily evapotranspiration (ET) at Carson Meadow ET site for 1996
13. Graphs showing measured annual precipitation and calculated daily evapotranspiration in Ash Meadows area, Nevada 
14-15. Graphs showing daily changes in measured water level and in calculated evapotranspiration, March 30 to April 8, 1996 at:
  14. Fairbanks Swamp ET site 
  15. Carson Meadow ET site
16. Graphs showing annual precipitation measured in Ash Meadows and reported at long-term weather stations in general area, 1980-97
17. Graph of water-table fluctuations measured at ET sites, January 1, 1994, to February 8, 1998
18. Graphs showing annual water-level fluctuation in a deep and two shallow wells, May 5, 1994, to October 9, 1995
19-22. Graphs showing annual water-level fluctuation in selected deep and shallow wells:
  19. March 10, 1996, to July 22, 1997
  20. April 10, 1994, to July 22, 1997
  21. April 10, 1994, to July 22, 1997
  22. April 10, 1994, to July 22, 1997
23-24. Graphs showing daily water-level fluctuation in selected deep and shallow wells: 
  23. August 28 to September 26, 1995
  24. September 7 to October 6, 1996
25. Graphs showing air pressure and daily water-level fluctuation in selected deep and shallow wells, January 15 to March 15, 1995

TABLES

1. Land covers represented by spectral clusters identified in June and September 1992 thematic mapper imagery of Ash Meadows area, Nevada

2. Pixel classification for combined June and September 1992 thematic mapper imagery

3. Evapotranspiration units determined from spectral-cluster combinations

4. Reclassification scheme used to assign evapotranspiration units from cluster combinations developed by combining June and September 1992 classifications

5. Accuracy assessment of evapotranspiration-unit classification

6. Location and general description of sites equipped with micrometeorological instruments and used to determine evapotranspiration

7. Estimated annual evapotranspiration at ET sites

8. Summary of annual fluctuations in water levels measured in shallow water-table wells and at staff gage

9. Summary of annual fluctuations in water levels measured in selected existing wells

10. Acreage and mean annual evapotranspiration (ET) estimates for ET units and totals for Ash Meadows area

11. Estimates of mean annual ground-water discharge

12. Shallow wells installed and measured during study

13. Existing wells measured during study

CONVERSION FACTORS AND VERTICAL DATUM

Multiply
By
 To obtain
Length
foot (ft)
0.3048 meter
inch (in.)
25.4 Millimeter
mile (mi)
1.609 Kilometer
Area
acre
0.4047 square hectometer
Volume
acre-foot (acre-ft)
0.001233 cubic hectometer
Energy Flux
watts per square feet (W/ft2)
0.0929 watt per square meter
Pressure
pound per square inch (lb/in2) 6.89476 KiloPascal
Velocity or Rate
foot per year (ft/yr)
0.3048 meters per year
foot per second (ft/s)
0.3048 meters per second
Volumetric Rate
acre-foot per year (acre-ft/yr)
0.001233 cubic hectometer per year
gallons per minute (gal/min)
0.0631 liter per second 

Temperature: Degrees Fahrenheit can be converted to degrees Celsius by the formula °C = (°F - 32) x 0.556.

Sea level: Sea level refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929), which formerly has been called the "Sea-Level Datum of 1929." The Datum is derived from a general adjustment of the first-order leveling networks across the United States and Canada.

Note: English units are used throughout this report, except in instances where a measurement has no common English-unit equivalent.

SYMBOL OR ACRONYM AND DEFINITIONS

Ca Specific heat of air at a constant pressure
Cs Specific heat of dry soil
Cw Specific heat of water
dbls Depth below land surface at which heat flux is measured
dbws Depth below water surface over which temperature is measured
de/dze Vapor pressure gradient near the Earth's surface
DGV Dense grassland vegetation
DMV Dense meadow vegetation
dT/dzt Temperature gradient near the Earth's surface
DWV Dense wetland vegetation
E Rate of water evaporation
e Vapor pressure
Ea Available energy
el,u Vapor pressure at lower or upper reference point
ERP Environmental Restoration Program
ET Evapotranspiration
G Subsurface heat flux
H Sensible heat flux
HFs Heat flux through soil at some measurement depth
kh Turbulent transfer coefficient of heat in air
kv Turbulent transfer coefficient of vapor
MBS Moist bare soil
NTS Nevada Test Site
OWB Open-water body
P Ambient air (barometric) pressure
RLi Incoming long wave radiation
RLo Outgoing long wave radiation
Rn Net radiation
RSi Incoming short wave radiation
RSo Outgoing short wave radiation
SAV Submerged aquatic vegetation
SGV Sparse grassland vegetation
SPOT Systeme Probatoire d'Observation de la Terre
T Temperature
Tl,u Temperature at lower or upper reference point
TM Thematic mapper
USDOE United States Department of Energy
USGS United States Geological Survey
W Gravimetric soil water content
ze Height at which vapor pressure is measured 
zt Height at which temperature is measured
d Ts Change in soil temperature between surface and soil heat flux measurement depth per unit time
d Tw Change in water temperature per unit time
e Ratio of molecular weight of water to dry air
gc Psychrometric constant
l Latent heat of vaporization for water
lE Latent heat flux
ra Density of air
rBs Bulk density of soil
rw Density of water