U.S. Geological Survey

Water-Resources Investigations Report

U.S. Department of the Interior

Comparison of Irrigation Water Use Estimates

Calculated From Remotely Sensed Irrigated

Acres and State Reported Irrigated Acres in the

Lake Altus Drainage Basin, Oklahoma and Texas,

2000 Growing Season

03-4155

Prepared in cooperation with the

BUREAU OF RECLAMATION
U.S. Geological Survey

Water-Resources Investigations Report

U.S. Department of the Interior

Comparison of Irrigation Water Use Estimates

Calculated From Remotely Sensed Irrigated

Acres and State Reported Irrigated Acres in the

Lake Altus Drainage Basin, Oklahoma and Texas,

2000 Growing Season

By Jason R. Masoner1, Carol S. Mladinich2, Alexandria M. Konduris2, and S. Jerrod Smith1

03–4155

Prepared in cooperation with the

BUREAU OF RECLAMATION

1

U.S. Geological Survey–Water Resources Discipline

2

U.S. Geological Survey–Geography Discipline
Masoner, J.R., and others—Comparison of Irrigation Water Use Estimates in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season—USGS/

WRIR 03–4155

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U.S. Department of the Interior

GALE A. NORTON, Secretary

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CHARLES G. GROAT, Director

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iii

Contents

Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Description of study area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Previous study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Historical freshwater withdrawals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Determination of land use and irrigated crop acres by remote sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Preprocessing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Accuracy assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Suggestions to increase accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Limitations of landsat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Remotely sensed irrigated crop acres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Irrigated crop acres from state water boards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Irrigation water requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Reference evapotranspiration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Crop evapotranspiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Effective precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Determination of irrigation water requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Irrigation water use calculated from remotely sensed irrigated crop acres. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Irrigation water use calculated from state reported irrigated acres. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Comparison of irrigation water use calculated from remotely sensed irrigated acres

with irrigation water use calculated from state reported irrigated acres. . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Selected references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Appendix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

1. Remote sensing classification categories shown with number of pixels and acres for the

part of Beckham County, Oklahoma, in the Lake Altus drainage basin during the

2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

2. Remote sensing classification categories shown with number of pixels and acres for the

part of Carson County, Texas, in the Lake Altus drainage basin during the

2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3. Remote sensing classification categories shown with number of pixels and acres for the

part of Donley County, Texas, in the Lake Altus drainage basin during the

2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4. Remote sensing classification categories shown with number of pixels and acres for the

part of Gray County, Texas, in the Lake Altus drainage basin during the

2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

5. Remote sensing classification categories shown with number of pixels and acres for the

part of Greer County, Oklahoma, in the Lake Altus drainage basin during the

2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

6. Remote sensing classification categories shown with number of pixels and acres for the

part of Kiowa County, Oklahoma, in the Lake Altus drainage basin during the

2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
iv

7. Remote sensing classification categories shown with number of pixels and acres for the

part of Potter County, Texas, in the Lake Altus drainage basin during the

2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

8. Remote sensing classification categories shown with number of pixels and acres for the

part of Roger Mills County, Oklahoma, in the Lake Altus drainage basin during the

2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

9 Remote sensing classification categories shown with number of pixels and acres for the

part of Washita County, Oklahoma, in the Lake Altus drainage basin during the

2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

10. Remote sensing classification categories shown with number of pixels and acres for the

part of Wheeler County, Texas, in the Lake Altus drainage basin during the

2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

Figures

1. Map showing the location of the Lake Altus drainage basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.Landsatimageshowinganexampleofaratio-classifiedimage.Thebrightnessofpixels

represents values for the ratio of band 4 to band 3. The brighter the pixel, the higher the

ratio and the healthier and greener the vegetation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.SchematicshowinglocationsandnamesofLandsatscenesusedtoacquireLandsat7

Enhanced Thematic Mapper Plus imagery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.Landsatimageshowingexampleofground-referencedatausedtooverlayand

classify imagery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5-10. Graphs showing:

5. Irrigatedcrop acresin the LakeAltus drainagebasin during the2000 growingseason,

determined using remote-sensing techniques and Landsat imagery . . . . . . . . . . . . . . . . . . . . . . . . 12

6. Irrigatedcrop acresin the LakeAltus drainagebasin during the2000 growingseason,

reported from the Oklahoma Water Resources Board and the Texas Water

Development Board. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7. Irrigation water use for crops in the Lake Altus drainage basin during the 2000 growing

season, calculated from remotely sense irrigated acres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

8. Irrigation water use for crops in the Lake Altus drainage basin during the 2000 growing

season, calculated from irrigated acres reported from the Oklahoma Water

Resources Board and the Texas Water Development Board. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

9.Comparisonofirrigationwaterusecalculatedfromremotelysensedirrigatedacres

with irrigation water use calculated from irrigated acres reported from the Oklahoma

Water Resources Board and Texas Water Development Board in the Lake Altus

drainage basin during the 2000 growing season, shown by county. . . . . . . . . . . . . . . . . . . . . . . . . . 22

10.Comparisonofirrigationwaterusecalculatedfromremotelysensedirrigatedcropacres

with irrigation water use calculated from irrigated acres reported from the Oklahoma

Water Resources Board and Texas Water Development Board in the Lake Altus

drainage basin during the 2000 growing season, shown by crop . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Tables

1.PortionsofcountiesinOklahomaandTexasintheLakeAltusdrainagebasin . . . . . . . . . . . . . . . . . . . . . . . . 4

2.1995estimatedfreshwaterwithdrawalsforcatalogingunits11120301and11120302 . . . . . . . . . . . . . . . . . . 5
v

3. Categories of pixel classes used to define land use and irrigated crop acres in the Lake Altus

drainage basin during the 2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

4.IrrigatedcropacresderivedfromremotesensingtechniquesandLandsatimageryforportions

of counties in the Lake Altus drainage basin during the 2000 growing season . . . . . . . . . . . . . . . . . . . . . 12

5.IrrigatedcropacresreportedfromtheOklahomaWaterResourcesBoardandTexas

Water Development Board for portions of Oklahoma and Texas Counties in the Lake

Altus drainage basin during the 2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

6.Weatherstationsusedinstudy,climatedatafromSeptember1999toOctober2000 . . . . . . . . . . . . . . . . . 15

7.Referenceevapotranspiration(ETo)forcropgrowingseasonsintheLakeAltusdrainage

basin during the 2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

8.Crop evapotranspiration (ETc) for majorcrops inthe Lake Altusdrainage basinduring the

2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

9. Irrigation water requirements (U) for major crops in the Lake Altus drainage basin during the

2000 growing season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

10. Irrigation water use for portion of counties in the Lake Altus drainage basin during the 2000

growing season, calculated from remotely sensed irrigated acres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

11. Irrigation water use for portion of counties in the Lake Altus drainage basin during the 2000

growing season, calculated from irrigated acres reported from Oklahoma Water

Resources Board and the Texas Water Development Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Conversion Factors and Datum

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

acre 0.004047 square kilometer (km2)

square mile (mi2) 2.590 square kilometer (km2)

Volume

gallon (gal) 0.003785 cubic meter (m3)

acre-foot (acre-ft) 43,560 cubic feet (ft3

)

acre-foot (acre-ft) 1,233 cubic meter (m3

)

Flow rate

cubic foot (ft3) 7.48 gallon (gal)

million gallons per day (Mgal/d) 0.003785 cubic meter per day (m3/d)

Watts

langleys per day (lang/day) 1,004,140.8 watts per meter squared (watts/m2)
vi

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 × °C) + 32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C = (°F - 32) / 1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988

(NAVD 88).

Horizontal coordinate information is North American Datum of 1983 (NAD 83).
Comparison of Irrigation Water Use Estimates Calculated

From Remotely Sensed Irrigated Acres and State Reported

Irrigated Acres in the Lake Altus Drainage Basin,

Oklahoma and Texas, 2000 Growing Season

By Jason R. Masoner, Carol S. Mladinich, Alexandria M. Konduris, and S. Jerrod Smith

Abstract

Increased demand for water in the Lake Altus drainage

basin requires more accurate estimates of water use for irrigation. The U.S. Geological Survey, in cooperation with the U.S.

Bureau of Reclamation, is investigating new techniques to

improve water-use estimates for irrigation purposes in the Lake

Altus drainage basin. Empirical estimates of reference evapotranspiration, crop evapotranspiration, and crop irrigation water

requirements for nine major crops were calculated from September 1999 to October 2000 using a solar radiation-based

evapotranspiration model. Estimates of irrigation water use

were calculated using remotely sensed irrigated crop acres

derived from Landsat 7 Enhanced Thematic Mapper Plus imagery and were compared with irrigation water-use estimates calculated from irrigated crop acres reported by the Oklahoma

Water Resources Board and the Texas Water Development

Board for the 2000 growing season. The techniques presented

will help manage water resources in the Lake Altus drainage

basin and may be transferable to other areas with similar water

management needs.

Irrigation water use calculated from the remotely sensed

irrigated acres was estimated at 154,920 acre-feet; whereas, irrigation water use calculated from state reported irrigated crop

acres was 196,026 acre-feet, a 23 percent difference. The greatest difference in irrigation water use was in Carson County,

Texas. Irrigation water use for Carson County, Texas, calculated from the remotely sensed irrigated acres was 58,555 acrefeet; whereas, irrigation water use calculated from state

reported irrigated acres was 138,180 acre-feet, an 81 percent

difference. The second greatest difference in irrigation water

use occurred in Beckham County, Oklahoma. Differences

between the two irrigation water use estimates are due to the

differences of irrigated crop acres derived from the mapping

process and those reported by the Oklahoma Water Resources

Board and Texas Water Development Board.

Introduction

Increased demand for water in the Lake Altus drainage

basin requires more accurate estimates of water use for irrigation. Agriculture is the primary land use in the drainage basin.

Ninety-one percent of water use in the drainage basin in 1995

was for irrigation purposes (R.L. Tortorelli, USGS, written

commun., 2001). Lake Altus supplies water to the Lugert-Altus

Irrigation District using a 270-mile system of canals downstream from the dam (Oklahoma Water Resources Board,

2000). Lake Altus was built by the Bureau of Reclamation from

1941 to 1948 for flood control, water supply for the City of

Altus, and irrigation of about 46,000 acres (A. Ensley, LugertAltus Irrigation District, oral commun., 2002). The LugertAltus Irrigation District annually supplies more than 85,000

acre-feet of water for agricultural purposes (Oklahoma Water

Resources Board, 2000).

The U.S. Geological Survey, in cooperation with the U.S.

Bureau of Reclamation, investigated new techniques to

improve water-use estimates for irrigation purposes in the Lake

Altus drainage basin (fig. 1). Empirical estimates of reference

evapotranspiration, crop evapotranspiration, and crop irrigation

water requirements for alfalfa, corn, cotton, hay, peanuts, sorghum, soybeans, sunflowers, and wheat were calculated on a

monthly and seasonal basis from September 1999 to October

2000 using an evapotranspiration model by Doorenbos and

Pruitt (1977). The model is commonly referred to as the radiation method and is accurate in arid and sub-humid areas and less

accurate near the ocean in cooler climates (U.S. Department of

Agriculture, 1993). These empirical estimates of irrigation

water use were used with estimated irrigated acres to calculate

irrigation water use in the Lake Altus drainage basin in Oklahoma and Texas.

Purpose and Scope

The purpose of this report is to present the techniques and

results of an effort to map irrigated crop acres in the Lake Altus

drainage basin using satellite imagery and remote sensing tech-
2 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

McClellan

Creek

Creek

Sweetwater

North

Fork

Red

River

LakeMcClellan

LakeAltus

GRAY

CARSON

DONLEY

WHEELER

BECKHAM

GREER

ARMSTRONG

ROGER MILLS

POTTER

COLLINGSWORTH RANDALL

HEMPHILL ROBERTS

WASHITA

KIOWA

HARMON

HUTCHINSON MOORE

11120301 11120302

07301500

101°30'W

101°30'W

101°0'W

101°0'W

100°30'W

100°30'W 100°0'W

100°0'W

99°30'W

99°30'W

35°0'N

35°0'N

35°30'N

35°30'N

OKLAHOMA

TEXAS

Altus

Amarillo OKLAHOMA

TEXAS

Map compiled by U.S. Geological SurveyBase map from National Elevation DatasetUniversal Transverse Mercator projection, Zone 14North American Datum 1983

Red

River

0 10 20 5 MILES

0 10 20 5 KILOMETERS

EXPLANATION

State boundaryCounty boundary

Stream

Elevation, in feet (NAVD 88)

3,6641,492

North Fork Red River study area andHydrologic Unit Code number (11120301)

07301500

USGS streamflow gage and number

CUSTER

Figure 1. Map of the Lake Altus drainage basin.
Introduction 3

niques, and compare irrigation water use estimates calculated

from the remotely sensed irrigated acres with those calculated

from state reported irrigated crop acres for the 2000 growing

season. This report presents: (1) mapping of land use and irrigated crop acres from multiple dates of Landsat 7 Enhanced

Thematic Mapper Plus (ETM+) imagery; (2) reported irrigated

crop acres from Oklahoma Water Resources Board (OWRB)

and Texas Water Development Board (TWDB); (3) seasonal

estimates of reference evapotranspiration, crop evapotranspiration, and crop irrigation water requirements; (4) seasonal estimates of irrigation water use for alfalfa, corn, cotton, hay,

peanuts, sorghum, soybeans, sunflowers, and wheat; and (5) a

comparison of irrigation water use estimates calculated from

remotely sensed irrigated acres and irrigation water use estimates calculated from the state reported irrigated acres.

Seasonal irrigation water use, referred to in this report as

irrigation water use during the 2000 growing season, was calculated for each crop on a countywide basis for major crops by

multiplying seasonal irrigation requirements by the number of

irrigated crop acres in each county. Irrigation water use was calculated using two sources of irrigated crop acres: (1) irrigated

crop acres derived from remote sensing techniques and Landsat

7 ETM+ imagery, referred to as remotely sensed irrigated acres;

and (2) irrigated acres reported by the OWRB and the TWDB,

referred to as state reported irrigated acres. Irrigation water use

estimates calculated from remotely sensed irrigated crop acres

were compared with irrigation water use estimates calculated

from state reported irrigated acres for the 2000 growing season.

Estimates of water use for irrigation provided in this report

will facilitate better management of water resources in the Lake

Altus drainage basin. Methodologies described in this report to

calculate estimates of reference evapotranspiration, crop evapotranspiration, crop irrigation water requirements, and irrigation

water use, may be transferable to other areas that may have similar water management needs. The irrigation water requirements presented in this report can be used with estimates of irrigated acres from anywhere in the drainage basin to calculate

irrigation water use.

Description of Study Area

The study area consists of the Lake Altus drainage basin

(fig.1). Lake Altus is located on the border of Greer and Kiowa

Counties in southwestern Oklahoma, approximately 20 miles

north of the town of Altus. The drainage area for Lake Altus is

approximately 2,515 square miles, 399 square miles of which

are non-contributing (Blazs and others, 2001). Most of the

drainage basin, includes parts of Beckham, Carson, Gray, and

Wheeler Counties (table 1).

The North Fork Red River is the major source of surfacewater inflow for Lake Altus. The North Fork Red River is one

of five major tributaries of the Red River. U.S. Geological Survey streamflow-monitoring station 07301500, North Fork Red

River Near Carter, Oklahoma, recorded a mean annual flow of

93,230 acre-feet from 1945 through 2000 (Blazs and others,

2001). Average annual precipitation in the study area ranges

from about 18 inches in the west at the headwaters to 26 inches

near Lake Altus in the east (Daly and others, 1994).

Agriculture is the major land use and is mainly supported

by water from the High Plains Aquifer, also referred to as the

Ogallala Aquifer, and alluvial and terrace deposits along the

North Fork Red River.

The High Plains Aquifer is an unconsolidated and semiconsolidated aquifer of Tertiary age and associated alluvial and

terrace deposits are of Quaternary age (Havens and others,

1985, p. 348). The High Plains Aquifer consists mostly of fine

sand and silts with lesser quantities of clay, gravel, and minor

beds of limestone and caliche (Hart and others, 1976). Well

yields range from 100 to 1,000 gallons per minute; with some

yields exceeding 1,500 gallons per minute (Havens and others,

1985, p. 347).

The North Fork Red River alluvial and Beckham and

Tillman terrace deposits consist of silt, clay, and gravel grading

downward into fine to coarse sand (Havens and others, 1985, p.

348). Well yields range from 100 – 200 gallons per minute in

the alluvium and 200 – 500 gallons per minute in the Beckham

and Tillman terrace (Havens and others, 1985, p. 348).

The length of growing season for crops is closely related

to temperature and has a substantial effect on the amount of

water used by crops. There are two primary growing seasons in

the Lake Altus drainage basin. Winter wheat is grown in the

first growing season, which occurs from early October through

early May (peak greenness), with harvesting in early June

(McDaniels, 1960, and U.S. Department of Agriculture, 1998).

Corn, cotton, peanuts, sorghum, soybeans, and sunflowers are

grown in the second growing season, which occurs from midMarch through late July to mid-August (peak greenness) with

harvesting in September or November (McDaniels, 1960, and

U.S. Department of Agriculture, 1998).

Previous Study

Heimes and Luckey (1982) describe a method for estimating historical irrigation water requirements for the High Plains

Aquifer from 1949 though 1978. There were two primary

components used to estimate irrigation water use; irrigated crop

acres and crop irrigation requirements. The report by Heimes

and Luckey (1982) acquired estimates of irrigated acres by

county from the Census of Agriculture (U.S. Department of

Commerce, 1949 to 1978). A modified version of the BlaneyCriddle formula was used to estimate irrigation water requirements for major crops growing above the High Plains Aquifer

(U.S. Department of Agriculture, 1970). The Modified BlaneyCriddle differs from the original Blaney-Criddle in that two

adjustment factors are used to better estimate crop evapotranspiration. A climate coefficient correlates monthly crop evapotranspiration with the mean monthly temperature, and a growthstage coefficient tracks crop growth development throughout

the growing cycle. The Modified Blaney-Criddle method is
4 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Table 1. Portions of counties in Oklahoma and Texas in the Lake Altus drainage basin

Counties State Portion of county in

drainage basin (acres)

Portion of county in

drainage basin (percent)

Beckham Okla. 365,310 20.4

Greer Okla. 47,686 2.7

Kiowa Okla. 32,384 1.8

Roger Mills Okla. 94,737 5.2

Washita Okla. 2,551 0.1

Carson Tex. 264,860 14.7

Donley Tex. 7,101 0.4

Gray Tex. 471,616 26.3

Randall Tex. 1,227 0.1

Potter Tex. 40,104 2.2

Wheeler Tex. 467,473 26.1

widely used because of the limited climate information needed

to calculate crop evapotranspiration and has been widely used

historically by federal and state agriculture programs. There are

more accurate methods that use solar radiation, wind speed,

temperature, and humidity data to estimate crop evapotranspiration (U.S. Department of Agriculture, 1970).

Historical Freshwater Withdrawals

Freshwater withdrawal estimates for 1995 were obtained

for 8-digit Hydrologic Unit Code (HUC) 11120301 and

11120302 (fig. 1) from the U.S. Geological Survey (R.L. Tortorelli, USGS, written commun., 2001). Total consumptive use

from the Lake Altus drainage basin was estimated to be 120,983

acre-feet or 108.15 million gallons per day. Consumptive use

for irrigation was estimated to be 109,781 acre-feet or 98.24

million gallons per day (table 2). Ground water supplies about

69 percent of total self-supplied water withdraws in the drainage basin; whereas, surface water accounts for the remaining 31

percent. The western half (11120301) of the study area

accounted for 61 percent of the total self-supplied withdrawals

in the drainage basin because of greater withdrawals from the

High Plains Aquifer for irrigation. Withdrawals in the western

half (11120301) are predominantly supplied by ground water

(94 percent); whereas, withdrawals in the eastern half

(11120302) are predominantly supplied by surface water (72

percent) (table 2).

Irrigation accounts for 82 percent of total self-supplied

water withdrawals in the drainage basin. However, the majority

of surface-water withdrawals and irrigated acres in the eastern

half are utilized downstream in the Altus-Lugert Irrigation District. The distribution of other less prevalent self-supplied withdrawals included 4.9 percent for public use, 4.5 percent for livestock use, 4.4 percent for industrial use, 3.6 percent for mining

use, and 0.4 percent for domestic use (calculated from table 2).

Detailed explanations of water use terms used in this section

can be acquired at URL http://ok.water.usgs.gov/wateruse/definitions.html

Acknowledgments

The authors wish to express their appreciation to personnel

from U.S. Department of Agriculture, Natural Resources Conservation Service (NRCS) and Farm Service Agency (FSA)

offices for providing field maps of croplands and information

about agricultural practices that were used to calibrate remote

sensing data when determining irrigated croplands. Howard

Johnson, Oklahoma Climatological Survey (OCS) and Cleon

Napkin, NRCS, provided climate data used in this report. Jerry

Walker and Tom Spofford, NRCS, provided technical advice

about the evapotranspiration model used for this report.

Michael Sughru, U.S. Geological Survey made several suggestions to improve the remote sensing part of this report.
Introduction 5

Table 2. 1995 estimated freshwater withdrawals for cataloging units 11120301 and 11120302 (data source, R.L. Tortorelli, U.S. Geological

Survey, written commun., 2001)

[data units in million gallons per day (mgd) unless noted; gal/day, gallon per day]

Public supply category 1120301 1120302 Total

basin Commercial category 1120301 1120302 Totalbasin

Population served by

ground water, in thousands

 7.64 20.21 27.85 Total self-supplied withdrawals, ground water0.07 0.25 0.32

Population served by surface water, in thousands 4.64 0.00 4.64 Total self-supplied withdrawals, surface water0.00 0.00 0.00

Total population served,

in thousands

 12.28 20.21 32.49 Total self-supplied withdrawals0.07 0.25 0.32

Total self-supplied withdrawals, ground water 1.25 4.74 5.99 Consumptive use, total 0.04 0.10 0.14

Total self-supplied withdrawals, surface water 0.00 0.00 0.00

Total self-supplied withdrawals, total 1.25 4.74 5.99

Per-capita use, in gal/d 101.79 234.53 184.36

Domestic category 1120301 1120302 Total

basin Industrial category 1120301 1120302 Totalbasin

Self-supplied population,

in thousands

 1.20 1.85 3.05 Total self-supplied withdrawals, ground water 5.19 0.20 5.39

Total self-supplied withdrawals, ground water 0.26 0.21 0.47 Total self-supplied withdrawals, surface water 0.00 0.00 0.00

Total self-supplied withdrawals, surface water 0.00 0.00 0.00

Total self-supplied withdrawals

 5.19 0.20 5.39

Total self-supplied withdrawals 0.26 0.21 0.47 Consumptive use, total 0.34 0.04 0.38

Per-capita use, self-supplied, in gal/d 216.67 113.51 154.10

Per-capita use, public-supplied, in gal/d194.63 95.99 133.27

Consumptive use, total 1.06 0.73 1.79

Mining category 1120301 1120302 Total

basin Total livestock category 1120301 1120302 Totalbasin

Total self-supplied withdrawals, ground water 3.65 0.73 4.38 Total self-supplied withdrawals, ground water 0.66 0.63 1.29

Total self-supplied withdrawals, surface water 0.00 0.00 0.00 Total self-supplied withdrawals, surface water 1.84 2.25 4.09
6 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated

Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Mining

category—Continued 1120301 1120302 Totalbasin

Total livestock

category—Continued 1120301 1120302 Totalbasin

Total self-supplied withdrawals 3.65 0.73 4.38 Total self-supplied withdrawals 2.50 2.88 5.38

Consumptive use, total 2.12 0.10 2.22 Consumptive use, total 2.50 2.88 5.38

Irrigation category 1120301 1120302 Total

basin

Reservoir evaporation

category 1120301 1120302 Totalbasin

Total self-supplied withdrawals, ground water59.09 6.80 65.89 Reservoir surface area, in

thousand acres

 0.32 4.74 5.06

Total self-supplied withdrawals, surface water 2.41 31.80 34.21 Reservoir evaporation, in

thousand acre-feet per

year

 1.59 23.16 24.75

Total self-supplied withdrawals 61.50 38.60 100.10

Consumptive use, total 61.50 36.74 98.24

Conveyance loss 0.00 1.59 1.59 Totals, overall category 1120301 1120302 Total

basin

Thousand acres irrigated,

sprinkler

 22.10 11.35 33.45 Total self-supplied withdrawals, ground water 70.17 13.56 83.73

Thousand acres irrigated,

microirrigation

 0.01 0.13 0.14 Total self-supplied withdrawals, surface-water 4.25 34.05 38.30

Thousand acres irrigated,

surface water

 38.06 38.73 76.79 Total self-supplied withdrawals74.42 47.61 122.03

Thousand acres irrigated 60.17 50.21 110.38 Total consumptive use 67.56 40.59 108.15

Reclaimed wastewater 2.69 0.08 2.77 Total conveyance losses 0.00 1.59 1.59

Table 2. 1995 estimated freshwater withdrawals for cataloging units 11120301 and 11120302 (data source, R.L. Tortorelli, U.S. Geological

Survey, written commun., 2001)—Continued.

[data units in million gallons per day (mgd) unless noted; gal/day, gallon per day]
Introduction 7

Determination of land use and irrigated crop acres by

remote sensing

Enhanced Thematic Mapper Plus (ETM+) (U. S. Geological Survey, 2002a) imagery was used to map land use and irrigated croplands during the 2000 growing season. Land use was

mapped using a supervised clustering algorithm based on statistical signatures for 25 pixel classes (table 3). Ancillary information from the National Land Cover Dataset 1992 (NLCD) (U.S.

Geological Survey, 2002b) and ground reference crop data from

the FSA county offices were used to aid in the development of

spectral signatures used to classify pixel classes. The NLCD is

categorized into broad land-cover types and identifies three

classes of agriculture: row crops, small grains, and hay/pasture.

These classes were used as an ancillary data source to aid in the

crop delineation.

Irrigated crop acres were determined using a ratio vegetation index consisting of a near infrared band (band 4) divided by

a visible red band (band 3) ratio to create the vegetation index

(Qi and others, 2002). The near infrared band and visible red

band ratio enhances certain features such as greenness of vegetation not generally visible. The resulting images consisted of a

single gray-scale band with bright white pixels representing

irrigated crop acres (fig. 2). Non-irrigated vegetation was displayed as ranges of gray. A threshold value was selected at

which everything greater than that value was considered to be

irrigated; everything less than that value was considered to be

non-irrigated. Threshold values were selected for each Landsat

scene based on the radiometric balancing applied to each Landsat scene. Some editing was required to remove riparian areas

or to add known irrigated agriculture that was less than the

threshold value. Appendices 1 through 10 provide county-specific information on the number of pixels and number of acres

for 25 land use classes in parts of each county in the drainage

basin determined from the mapping process. A null pixel class

is listed in the appendices and represents the part of a county

that is outside the portion of the drainage basin in the county.

Identification of crop types with Landsat 7 ETM+ satellite

imagery is a routine application of remote sensing technology.

Image date selection is vital for successful identification of

many vegetation covers, especially agricultural crops

(Rundquist and others, 2002). Identification of agricultural

crops using satellite imagery requires knowledge of crop phenology, climate for the particular growing season, and ground

reference information about specific agricultural practices in

the drainage basin. The best date range to identify winter wheat

is between late March through early May, when wheat is at peak

greenness. To identify corn and other summer crops, the best

date range is late July to mid-August.

The original study plan was to use the same imagery used

in the generation of the NLCD and in the High Plains Aquifer

study (Qi and others, 2002) because two dates were used, a winter leaf-off date and a summer leaf-on date. However, these

dates were less than optimal for crop delineation. The dates for

the selected imagery used for this report were selected to occur

Table 3. Categories of pixel classes used to define land use and irrigated crop acres in the Lake Altus

drainage basin during the 2000 growing season

Croplands General land use Irrigated croplands

Alfalfa Fallow Alfalfa

Corn Grasslands Corn

Cotton Trees Peanut

Cowpeas Urban Sorghum

Hay/Pasture Water Soybeans

Oats Unknown crops Wheat

Peanut Unknown irrigated

Rye

Sorghum

Soybeans

Sunflowers

Wheat
8 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Ratio-classified image, band 4 divided by band 3

Landsat image (bands 4, 3, and 2)

Figure 2. An example of a ratio-classified image. The brightness of pixels represents values for the ratio of band 4 to band 3. The

brighter the pixel, the higher the ratio and the healthier and greener the vegetation.
Introduction 9

Figure 3. Locations and names of Landsat scenes used to acquire Landsat 7 Enhanced Thematic Mapper Plus imagery.

during peak greenness periods for both winter wheat and

summer crops. The Lake Altus drainage basin spans four Landsat scenes used to acquire ETM+ images, Path/Row 30/35,36

and Path/Row 29/35,36 (fig. 3). Two dates were originally

selected for analysis. A spring date (Path/Row 30/35,36 – 5/20/

2000, Path/Row 29/35,36 – 5/13/2000) to map the winter wheat

and a summer date (Path/Row 30/35,36 – 7/23/2000, Path/Row

29/35,36 – 8/1/2000) to map the remainder of the crops in the

basin. Imagery from a third date (Path/Row 30/35,36 – 4/18/

2000, Path/Row 29/35,36 – 3/26/2000) was analyzed because

the winter wheat green-up was earlier in the season, which

caused harvesting to occur earlier than normal in Texas counties. The 2000 growing season was selected because it was

extremely dry all season in the Texas counties and dry in the

fall, winter, and late summer in the Oklahoma counties. Therefore, more irrigation was required than in a normal growing season, thus enabling better delineation between irrigated crops

and non-irrigated cropland and rangeland.

Preprocessing

The ETM+ is a multispectral scanning radiometer that is

carried on the Landsat 7 satellite. The ETM+ radiometer provides data from eight spectral bands and can be ordered in varying levels of calibration. Systematic correction Level 1G

images were used for this report. The Level 1G product incorporates both a radiometric and geometric correction to images.

The images are rotated to north, aligned, coarsely georeferenced to the Universal Transverse Mercator (UTM) projection,

and resampled to 28.5-meter pixel resolution using a nearest

neighbor algorithm (Research Systems Incorporated, 2001).

Two of the spectral bands are eliminated from processing: spectral band 1 because of data redundancy and thermal spectral

band 6 because it measures transmitted energy (the other bands

measure reflected energy).

The images were referenced to the UTM projection and

projected to fit the Albers equal-area projection. Individual

image scenes were merged and cropped to the basin boundary

to speed and facilitate processing. The final classification

images consisted of three composite images for the study area

two in early spring to map winter wheat and one in summer to

map the remaining crops. Mapping of land use and irrigated

croplands was done in two stages. The first stage consisted of

determining land use, the second stage consisted of determining

specific irrigated crops.

Ground-reference data were compiled from FSA and

NRCS county offices for each county in the basin using a ran-
10 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Landsat image (bands 4, 3, 2)

Landsat image (bands 4, 3, and 2)

overlain with ground-reference data

Figure 4. Example of ground-reference data used to overlay and classify imagery.

dom approach. A random selection of points was generated for

areas known to be, or thought to be, irrigated in the drainage

basin. Maps of these areas were sent to each FSA county office

in the drainage basin. County offices were asked to identify the

crop types and irrigation status. The data were generally provided as an annotated photocopy of the office aerial photograph

of the particular field in question. The field boundaries were

then digitized using the satellite image and annotated with the

comments provided by the FSA office (fig. 4). Half of the

returned ground-reference data were used in the generation of

training signatures and the other half were used for accuracy

assessment at the end of the analysis.

Accuracy Assessment

An accuracy assessment of the cell classifications was

completed for the drainage basin using ground-reference data.

Segments from four counties (Beckham, Carson, Gray, and

Greer) were used for the assessment. Confusion matrices (probability matrices of land-use classes) were generated using the

final classified image and the accuracy segments. An accuracy

of 69.6960 percent with a kappa coefficient of 0.0007 was

achieved. The low kappa coefficient was a result of the low

number of accuracy segments and the lack of representation of

all classes in the final classified image. In addition to the class

confusion matrix, errors of commission/omission, producer and

user accuracies also were examined.

Suggestions to Increase Accuracy

Two of the primary determinants of accuracy in defining

irrigated crops are the dates of the Landsat images and number

of the ground-reference data samples. To correlate the peak

growth of individual crops with the best Landsat image date,

there must be sufficient ground-truth data regarding the distribution of crop types and irrigation practices. Required information includes: (1) date of planting and harvest in order to interpolate the dates of peak growth and greenness, and (2) number

of harvested acres for each crop by county to determine the

number of ground-truth data to collect for each crop. With

knowledge of peak greenness of each crop in a given season, the

number of Landsat image dates can be better determined. For

example, the peak greenness for corn during the 2000 growing

season may have been in mid-June, but peak greenness for soybeans may have been in early June. In that case, two Landsat

image dates would be required to achieve the greatest accuracy

in determining irrigated crops.
Remotely Sensed Irrigated Crop Acres 11

Limitations of Landsat

Even with the correct date selection and ground-reference

data, there are limitations to using Landsat multispectral satellite imagery because of limitations of spectral range and spatial

resolution (5 multispectral bands at 30-meter spatial resolution). Some agricultural crops or vegetation species are too

spectrally similar to be differentiated by Landsat. Hyperspectral

sensors with broader spectral ranges and higher spatial resolutions may enable greater distinction of vegetation classes. With

multispectral sensors such as Landsat, there are only 5 broad

spectral bands (0.45 – 1.75 micrometers (μm)) of recorded

information; hyperspectral sensors can range from 36 to 224

spectral bands (0.45 – 2.5 μm) of recorded information.

With increased spectral range and spatial resolution, it is possible to identify subtle changes in chlorophyll absorption that

relate to different vegetation species and health of a vegetation

species. Currently, most hyperspectral sensors are on airborne

platforms such as Advanced Visible Infrared Imaging Spectrometer (AVIRIS) and Compact Airborne Spectrographic

Imager (CASI), but the number of satellite-borne hyperspectral

platforms such as Hyperion are increasing. Presently (2002),

there are two high spatial-resolution satellites (IKONOS and

QUICKBIRD) with 4-meter multi-spectral sensors.

Remotely Sensed Irrigated Crop Acres

Remotely sensed irrigated crop acres were determined for

portions of the following Oklahoma counties in the Lake Altus

drainage basin: Beckham, Greer, Kiowa, Roger Mills, and

Washita. Beckham County had the greatest number of irrigated

crop acres, followed by Roger Mills, Greer, Kiowa, and Washita (table 4). Alfalfa, peanuts, and wheat were the only crops

determined to be irrigated in the five counties. Irrigated acres of

alfalfa, peanuts, and wheat were greatest in Beckham County.

A total of 70 percent of irrigated wheat, 68 percent of irrigated

alfalfa, and 51 percent of irrigated peanuts in the Oklahoma

counties occurred in Beckham County.

Remotely sensed irrigated crop acres were determined for

the following Texas counties: Carson, Donley, Gray, Potter,

and Wheeler. Although a small portion of Randall County is

included in the drainage basin, there were no reported irrigated

crop acres in that county. Carson County had the greatest number of irrigated crop acres followed by Gray, Wheeler, Potter,

and Donley (table 4). Irrigated acres of corn, sorghum, soybeans, and wheat were greatest in Carson County. A total of 92

percent of irrigated sorghum, 63 percent of irrigated corn, 51

percent of irrigated wheat, and 49 percent of irrigated soybeans

in Texas counties occurred in Carson County. Wheeler County

had the largest number of irrigated alfalfa acres, representing 94

percent of the irrigated alfalfa in Texas counties.

Seventy-four percent of the total irrigated crop acreage in

the drainage basin occurred in Texas counties. One hundred

percent of irrigated corn, sorghum, and soybeans in the drainage

basin occurred in Texas. Eighty-nine percent or 38,677 acres of

irrigated wheat occurred in Texas. Irrigated peanuts and irrigated alfalfa acres were greater in Oklahoma than in Texas.

Eighty-one percent or 13,768 acres of irrigated alfalfa and 71

percent or 1,583 acres of irrigated peanuts were in Oklahoma.

There were 43,686 acres of irrigated wheat, or 56 percent

of the total irrigated crop acres in the drainage basin (fig. 5).

Irrigated alfalfa consisted of 22 percent of the total irrigated

crop acres in the drainage basin, irrigated corn consisted of 11

percent, and irrigated soybeans consisted of 6 percent. The

remaining 5 percent of irrigated crop acres in the drainage basin

consisted of peanuts and sorghum.

Irrigated crop acres from state water boards

Irrigated crop acres from the OWRB and the TWDB were

compiled and summarized for the 2000 growing season. The

OWRB collects irrigation information in Oklahoma about specific irrigated crops by county and by 8-digit HUC watershed.

Mail survey forms are sent out annually to registered water

users. Approximately 66 percent of registered water users

complete and return the irrigation surveys sent out by the

OWRB (Phyllis Robertson, Oklahoma Water Resources Board,

oral commun., 2002). Irrigated acres from the OWRB were

compiled for portions of Oklahoma counties in the Lake Altus

drainage basin (fig. 1) (Phyllis Robertson, Oklahoma Water

Resources Board, written commun., 2002).

The TWDB collects water use and irrigation information

for Texas using two survey compilation methods. The first survey reporting method collects information annually regarding

the sum of irrigated acres in a county and by 8-digit HUC watershed, but not specific information about individual crops that

are irrigated. The second survey is a detailed irrigation survey

and is a cooperative effort between the NRCS, U.S. Department

of Agriculture, the Texas State Soil and Water Conservation

Board, and the TWDB. This detailed survey is conducted at 5-

year intervals (Texas Water Development Board, 2000). Specific information about irrigated crop acres are recorded on a

countywide basis, but not on a watershed basis. A detailed irrigation survey was conducted in Texas counties during the 2000

growing season.

Irrigated crop acres in the drainage basin for Donley, Gray,

Potter, Randall, and Wheeler Counties in Texas were determined by dividing the portion of drainage basin in a county by

the total area of the county and multiplying the result by the

total irrigated crop acres in each county. Because the majority

of irrigation in Carson County occurred in and around the drainage basin, a boundary was digitized outlining the area in Carson

County where the majority of agriculture was present and irrigation was being applied. The irrigated crop acres in the drainage basin for Carson County were determined by dividing the

portion of the drainage basin in the county by the digitized area

instead of the total area of Carson County and multiplying
12 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Table 4. Irrigated crop acres derived from remote sensing techniques and Landsat imagery for portions of counties in the Lake Altus

drainage basin during the 2000 growing season

[–, not determined]

Counties State

Irrigated crops (acres)

Alfalfa Corn Peanuts Sorghum Soybeans Wheat Total

Beckham Okla. 9,297 – 807 – – 3,490 13,594

Greer Okla. 1,719 – 225 – – 599 2,543

Kiowa Okla. 691 – 225 – – 440 1,356

Roger Mills Okla. 2,003 – 315 – – 470 2,788

Washita Okla. 58 – 11 – – 10 79

Total Okla. 13,768 0 1,583 0 0 5,009 20,360

Carson Tex. 1 5,573 0 1,897 2,360 19,650 29,481

Donley Tex. 0 200 0 1 66 55 322

Gray Tex. 187 2,792 0 149 1,407 11,986 16,521

Randall Tex. – –––– ––

Potter Tex. 1 1 0 7 42 2,239 2,290

Wheeler Tex. 3,002 266 646 15 962 4,747 9,638

Total Tex. 3,191 8,832 646 2,069 4,837 38,677 58,252

Basin Total 16,959 8,832 2,229 2,069 4,837 43,686 78,612

8,832

4,837

43,686

2,229 2,069

16,959

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

Alfalfa Corn Peanuts Sorghum Soybeans Wheat

IRRIGATED CROPS

50,000

55,000

IRRIGATED ACRES

Figure 5. Irrigated crop acres in the Lake Altus drainage basin during the 2000 growing season, determined using remote-sensing techniques and Landsat imagery,
Irrigation water requirements 13

the result by the total irrigated crop acres in the county.

In the Oklahoma portion of the drainage basin, Beckham

County had the greatest number of reported irrigated crop acres,

followed by Greer, Kiowa, and Roger Mills (table 5). There

were no irrigated crop acres reported for the portion of Washita

County in the drainage basin. Alfalfa, corn, cotton, hay, peanuts, sorghum, and wheat were reported irrigated in the five

Oklahoma counties. A total of 69 percent of irrigated hay, 64

percent of irrigated sorghum, 62 percent of irrigated peanuts, 53

percent of irrigated wheat, and 51 percent of irrigated alfalfa in

Oklahoma counties occurred in Beckham County. A total of 99

percent of irrigated corn was reported in Kiowa County with

385 acres. Irrigated cotton was greatest in Roger Mills County,

representing 89 percent of the total irrigated cotton reported for

Oklahoma counties.

In the Texas portion of the drainage basin, Carson County

had the greatest number of reported irrigated crop acres followed by Gray, Wheeler, Potter, Donley, and Randall Counties

(table 5). Irrigated acres of alfalfa, corn, sorghum, soybeans,

sunflowers, and wheat were greatest in Carson County. A total

of 100 percent of irrigated sunflowers, 92 percent of irrigated

sorghum, 79 percent of irrigated wheat, 76 percent of irrigated

soybeans, 70 percent of irrigated corn, and 66 percent of irrigated alfalfa for Texas counties occurred in Carson County.

Irrigated cotton, hay, and peanuts were greatest in Wheeler

County. A total of 92 percent of irrigated peanuts, 73 percent of

irrigated cotton, and 70 percent of irrigated hay for Texas counties occurred in Wheeler County.

Irrigated crop acres for Texas counties reported by the

TWDB were 94 percent of the total reported irrigated acres in

the Lake Altus drainage basin (table 5). One hundred percent of

irrigated sunflowers and irrigated soybeans, 99 percent of irrigated wheat, 98 percent of irrigated sorghum and corn, and 91

percent of irrigated cotton in the drainage basin occurred in

Texas. Only irrigated alfalfa and irrigated peanuts had more

acreage in Oklahoma than in Texas (table 5).

There were 46,659 acres of irrigated wheat, or 47 percent of the

total irrigated crop acres in the drainage basin (fig. 6). Irrigated

corn comprised 17 percent of the total irrigated crop acres in the

drainage basin, irrigated soybeans comprised 11 percent, irrigated sorghum comprised 10 percent, and irrigated hay comprised 5 percent. The remaining 10 percent of irrigated crops

acres in the drainage basin consisted of peanuts, cotton, alfalfa,

and sunflowers.

Irrigation water requirements

The irrigation water requirements is the depth of irrigation

water, excluding precipitation, stored soil moisture, or ground

water, that is required consumptively for healthy crop production (U.S. Department of Agriculture, 1970). The irrigation

water requirement is calculated by subtracting crop evapoTable 5. Irrigated crop acres reported from the Oklahoma Water Resources Board and Texas Water Development Board for

portions of Oklahoma and Texas Counties in the Lake Altus drainage basin during the 2000 growing season

[–, not reported]

Counties State Irrigated crops (acres)

Alfalfa Corn Cotton Hay Peanuts Sorghum Soybeans Sunflowers Wheat Total

Beckham Okla. 672 2 10 784 1,561 116 – – 133 3,278

Greer Okla. 536 0 15 100 797 0 – – 60 1,508

Kiowa Okla. 0 385 0 98 156 65 – – 58 762

Roger Mills Okla. 100 0 210 150 0 0 – – 0 460

Washita Okla. – – – – – – – – – –

Total Okla. 1,308 387 235 1,132 2,514 181 0 0 251 6,008

Carson Tex. 663 11,182 488 495 0 8,551 8,228 2,172 36,850 68,629

Donley Tex. 30 16 75 33 43 33 7 0 34 271

Gray Tex. 236 4,417 43 493 0 649 2,611 0 7,756 16,205

Potter Tex. 79 24 14 79 0 29 0 0 185 410

Randall Tex. 1 3 2 2 0 19 0 0 25 52

Wheeler Tex. 0 300 1,711 2,612 506 60 0 0 1,558 6,747

Total Tex. 1,009 15,942 2,333 3,714 549 9,341 10,846 2,172 46,408 92,314

Basin Total 2,317 16,329 2,568 4,846 3,063 9,522 10,846 2,172 46,659 98,322
14 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

2,568 3,063

9,522

2,172

46,659

10,846

4,846

16,329

2,317

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

IRRIGATED CROPS

Alfalfa

Corn

Cotton

Hay

Peanuts

Sorghum

Soybeans

Sunflowers

Wheat

55,000

IRRIGATED ACRES

Figure 6. Irrigated crop acres in the Lake Altus drainage basin during the 2000 growing season, reported from the Oklahoma

Water Resources Board and the Texas Water Development Board.

transpiration by the amount of water available to the crop

through natural precipitation.

Climate conditions during the 2000 growing season were

extremely dry and hot in most of the study area and were not

representative of a typical growing season in the drainage basin.

Most of the precipitation occurred in March and June, with little

or no precipitation occurring in July, August, and September.

During July and August, average monthly temperatures ranged

from 80 degrees Fahrenheit in Roger Mills County to 90

degrees Fahrenheit in Kiowa County (Howard Johnson, Oklahoma Climatological Survey, written commun., 2001). There

were several consecutive days in July, August, and September

where temperatures exceeded 100 degrees Fahrenheit (Weldon

E. Sears, Natural Resources Conservation Service, oral commun., 2002). Based on the extremely hot and dry weather conditions during the 2000 growing season, estimates of irrigation

water use presented in this report are probably greater than for

a normal year. The values of irrigation water use in this report

are a measure of how much water crops could consume if it

were available during the growing season. Climate data from

September 1999 to October 2000 were used from weather stations listed in table 6.

Although the evapotranspiration model used for this report

can accurately predict evapotranspiration in 5-day increments

or longer in arid and non-humid environments (U.S. Department of Agriculture, 1993), other factors and assumptions made

while calculating crop evapotranspiration and irrigation water

requirements should be considered. Other factors such as irrigation practices, soil properties, water stress factors, and soil

evaporation that affect crop water use were not considered

when computing crop evapotranspiration for this report. The

actual soil intake rate and the rainfall intensities were not considered when calculating the effective precipitation. A soil

water storage factor of 1 was used to calculate the effective precipitation values used in this report. A soil water storage factor

of 1 refers to a 3-inch available soil water capacity in the crop

root zone.

The steps used to calculate the irrigation water requirements in this report include: (1) calculation of a referenced

evapotranspiration; (2) determination of crop evapotranspiration, and (3) calculation of effective precipitation. The following sections provide an overview of the steps used to calculate

irrigation water requirements.

Reference Evapotranspiration

An evapotranspiration model developed by Doorenbos

and Pruitt (1977), based on climate data from September 1999

through October 2000, was used to calculate seasonal estimates

of reference evapotranspiration (table 7) for major crops during

the 2000 growing season. The reference evapotranspiration
Irrigation water requirements 15

Table 6. Weather stations used in study, climate data from September 1999 to October 2000

U.S. Weather Service weather stations Oklahoma Mesonet weather stations

Counties State Station name Counties State Station name

BECKHAM Okla. ELK CITY ROGER MILLS Okla. Cheyenne (CHEY)

BECKHAM Okla. ERICK BECKHAM Okla. Erick (ERIC)

BECKHAM Okla. MORAVIA WASHITA Okla. Retrop (RETR)

BECKHAM Okla. RETROP KIOWA Okla. Hobart (HOBA)

BECKHAM Okla. SAYRE GREER Okla. Mangum (MANG)

BECKHAM Okla. SWEETWATER Texas A&M Agriculural Research and Extension Center weather stations

GREER Okla. MANGUM County State Station name

GREER Okla. WILLOW CARSON Tex. White deer

KIOWA Okla. ALTUS DAM

KIOWA Okla. HOBART

KIOWA Okla. ROOSEVELT

KIOWA Okla. SEDAN

KIOWA Okla. SNYDER

ROGER MILLS Okla. HAMMON

ROGER MILLS Okla. REYDON

WASHITA Okla. COLONY

WASHITA Okla. CORDELL

CARSON Tex. PANHANDLE

DONLEY Tex. CLARENDON

GRAY Okla. PAMPA

GRAY Okla. MC LEAN

POTTER Tex. AMARILLO

RANDALL Tex. UMBARGER

RANDALL Tex. CANYON

WHEELER Okla. SHAMROCK

WHEELER Okla. WHEELER
16 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Table 7. Reference evapotranspiration (ETo) for crop growing seasons in the Lake Altus drainage basin during the 2000 growing season

[–, not determined]

Counties State

Reference evapotranspiration for crop growing season (inches)

Alfalfa Corn Cotton Hay Peanuts Sorghum

SoybeansSunflowers Wheat

Beckham Okla. 51.5 39.2 38.9 38.9 28.1 33.6 33.6 – 35.8

Greer1, Kiowa1,

and Washita1 Okla. 53.4 41.4 41.4 41.2 30.0 33.6 35.6 – 37.1

Roger Mills Okla. 52.3 40.4 40.7 44.8 29.6 35.3 35.3 – 35.6

Carson Tex. 56.7 39.4 43.2 43.2 35.1 33.7 36.8 33.7 40.4

Potter2 Tex. 57.9 40.3 44.0 44.0 35.8 34.3 37.4 34.3 41.5

Gray2 Tex. 58.1 40.3 44.1 44.1 35.8 34.4 37.5 34.4 42.0

Wheeler1 Tex. 52.6 36.1 40.3 40.7 29.2 31.9 34.8 – 36.5

1

Climate data from Beckham County was used to calculate reference evapotranspiration.

2

Solar radiation data from Carson County was used to calculate reference evapotranspiration.

values differ due to the variable length of growing seasons for

different crops. Average monthly values of precipitation, barometric pressure, relative humidity, solar radiation, temperature,

and wind speed data were used to calculate reference evapotranspiration from October 1999 to September 2000. The Oklahoma Climatological Survey (OCS) provided climate data from

multiple weather stations from the National Weather Service

and the Oklahoma Mesonet to create monthly averages for portions of counties in the study area (Howard Johnson, Oklahoma

Climatological Survey, written commun., 2001) (table 6). Additional solar radiation and barometric pressure data were

acquired from Texas A&M Agricultural Research and Extension Center for Carson, Gray, and Potter Counties in Texas

(U.S. Department of Agriculture, 2001).

The model by Doorenbos and Pruitt (1977) is referred to as

the radiation method, which is very accurate in arid and subhumid areas (U.S. Department of Agriculture, 1993). The radiation method requires that a reference evapotranspiration rate

(ETo) be calculated and adjusted by a basal crop coefficient to

compute the rate of evapotranspiration for a specific crop (crop

evapotranspiration ETc). Reference evapotranspiration (ETo) is

a baseline rate of evapotranspiration for a clipped grass growing

under climatic conditions for a known time period. The radiation method from Doorenbos and Pruitt (1977) is expressed by

equation 1:

ETo=-0.012+(∆/∆+Υ)*br*Rs/λ (1)

where

ETo = reference evapotranspiration for a clipped grass,

in inches;

∆ = slope of the vapor pressure curve, in millibars per

degree Fahrenheit;

Υ = psychrometric constant, in millibars per degree

Fahrenheit;

br = adjustment factor depending on the average relative humidity and daytime wind speed, in miles

per day;

Rs = incoming solar radiation in langleys per day; and

λ = heat of vaporization of water, in langleys per day

Crop Evapotranspiration

Crop evapotranspiration (ETc) is an empirical estimate of

the total amount of water required for a crop growing in an area

under known climate conditions so that crop production is not

limited by lack of water. Crop evapotranspiration is determined

by adjusting the reference evapotranspiration (ETo) to fit a basal

crop coefficient curve. A basal crop coefficient curve represents

the water use of a healthy, well-watered crop where the soil surface is dry (U.S. Department of Agriculture, 1993). The crop

coefficient system developed by Doorenbos and Pruitt (1977)

and modified by Howell and others (1986) was used to calculate

monthly estimates of crop evapotranspiration (ETc) for the nine

major crops being irrigated during the 2000 growing season.

Crop evapotranspiration (ETc) is calculated using the reference

evapotranspiration (ETo) and a basal crop coefficient (Kcb). The

formula used to calculate crop evapotranspiration is expressed

by equation 2 (U.S. Department of Agriculture, 1993; Doorenbos and Pruitt, 1977):

ETc=Kcb*ETo (2)

where

ETc = rate of crop evapotranspiration, in inches;
Irrigation water requirements 17

Kcb = basal crop coefficient relating actual crop evapotranspiration (ETc) to reference evapotranspiration (ETo); and

ETo = reference evapotranspiration for a clipped grass

reference crop, in inches

The basal crop coefficient (Kcb) is a factor that relates reference evapotranspiration (ETo) to actual crop evapotranspiration (ETc). The method outlined by Doorenbos and Pruitt

(1977) divides the growing season for a particular crop into four

growing stages and calculates multiple basal crop coefficients

at defined increments throughout each growing stage using

equations and parameters in U.S. Department of Agriculture

(1993, fig. 2-21 and table 2-20). Crop evapotranspiration for the

growing season was calculated for alfalfa, corn, cotton, hay,

peanuts, sorghum, soybeans, sunflowers, and wheat for portions

of counties in the Lake Altus drainage basin (table 8).

Effective Precipitation

Effective precipitation (fe) is the amount of precipitation

that is available to meet the evapotranspiration requirements of

crops. Monthly average values of precipitation for each county

of the drainage basin from September 1999 to October 2000

were provided by the OCS (Howard Johnson, Oklahoma Climatological Survey, written commun., 2001) and were used to calculate effective precipitation. Equation 3 was used to calculate

effective precipitation (fe) (U.S. Department of Agriculture,

1970):

fe=(0.7091747*rt

0.82416–0.11556)*(100.02426*ETc)*f (3)

where

fe = average monthly effective precipitation, in

inches;

rt = average monthly precipitation, in inches;

ETc = rate of crop evapotranspiration, in inches; and

f = soil water storage factor (dimensionless)

Determination of Irrigation Water Requirements

The irrigation water requirement (U) is calculated by subtracting the amount of water available to the crop through natural precipitation (effective precipitation, fe) from the crop

evapotranspiration (ETc). Irrigation water requirements (U) for

the growing season were calculated on a countywide basis for

each of the irrigated crops (table 9). The formula used to calculate irrigation water requirement is expressed by equation 4

(U.S. Department of Agriculture, 1970):

U=ETc–fe (4)

where

U = irrigation water requirement, in inches;

ETc = rate of crop evapotranspiration, in inches; and

fe = effective precipitation, in inches

Table 8. Crop evapotranspiration (ETc) for major crops in the Lake Altus drainage basin during the 2000 growing season

[–, not determined]

Counties State

Crop evapotranspiration for crop growing season (inches)

Alfalfa Corn Cotton Hay Peanuts Sorghum

SoybeansSunflowers Wheat

Beckham Okla. 38.9 31.0 33.6 29.1 20.9 27.0 28.8 – 26.5

Greer1,

Kiowa1, and

Washita1

1

Climate data from Beckham County was used to calculate crop evapotranspiration.

Okla. 40.3 33.0 35.5 30.8 22.2 28.5 30.3 – 27.1

Roger Mills Okla. 39.7 32.3 35.4 32.2 22.2 28.6 30.3 – 25.9

Carson Tex. 42.9 31.0 37.0 32.1 26.5 26.8 31.5 27.4 30.3

Potter Tex. 43.8 31.6 37.6 32.7 27.0 27.3 32.1 27.9 31.2

Gray Tex. 43.9 31.6 37.8 32.7 27.1 27.0 32.2 28.0 42.0

Wheeler Tex. 39.8 28.8 34.9 30.5 21.8 25.5 29.8 – 26.7
18 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Table 9. Irrigation water requirements (U) for major crops in the Lake Altus drainage basin during the 2000 growing season

[–, not determined]

Counties State

Irrigation water requirements (inches)

Alfalfa Corn Cotton Hay Peanuts Sorghum

SoybeansSunflowers Wheat

Beckham Okla. 27.1 22.8 27.3 21.9 18.7 24.2 26 – 16.6

Greer, Kiowa,

and Washita Okla. 26.7 23.8 28.2 17.2 18.9 24.4 26.2 – 17.2

Roger Mills Okla. 28.6 24.7 29.6 24.8 19.9 25.4 27.2 – 16

Carson Tex. 31.8 22.4 30.0 24.0 24.2 23.8 27.6 24.2 23.8

Potter Tex. 34.9 25.9 32.1 26.4 24.7 24.7 29.7 26.1 25.5

Gray Tex. 31.6 22.0 30.5 24.8 24.8 24.5 28.3 25.1 22.6

Wheeler Tex. 29 20.8 29.1 23.7 19.9 23.6 27.2 18.5 18.5

Irrigation Water Use Calculated From

Remotely Sensed Irrigated Crop Acres

Irrigation water use is defined as the amount of water supplied through irrigation so that crop yields are not limited.

Empirical estimates of irrigation water use for the 2000 growing

season were calculated as the product of the irrigation water

requirements (table 9) and irrigated crop acres determined from

remote-sensing techniques (table 4).

An estimated total of 154,920 acre-feet of water were used

for irrigation in the Lake Altus drainage basin during the 2000

growing season (table 10). Seventy-four percent of the irrigation water use in the drainage basin occurred in Texas counties

(table 10). Irrigation water use was greatest in Carson County,

Texas, with an estimated 58,555 acre-feet or 38 percent of irrigation water use in the drainage basin (table 10). Gray County

accounted for 21 percent of irrigation water use in the drainage

basin; whereas, Wheeler County accounted for 12 percent of

irrigation water use. Irrigation water use for the portion of the

drainage basin in Oklahoma was greatest in Beckham County

with an estimated 27,076 acre-feet or 17 percent of the total irrigation water use in the drainage basin (table 10).

Irrigation water use was greatest for wheat, with an estimated 80,692 acre-feet, or 52 percent of the total irrigation

water use in the drainage basin (fig. 7). Irrigation water use for

alfalfa was 39,011 acre-feet, or 25 percent of the total irrigation

water use. The distribution of irrigation water use for other

crops in the drainage basin was 11 percent corn and 7 percent

soybeans, with peanuts and sorghum making up the remaining

5 percent. Irrigation water use for corn, sorghum, soybeans, and

wheat was greatest in Carson County, Texas; whereas, most of

the irrigation water use for alfalfa and peanuts occurred in

Beckham County, Oklahoma (table 10).

Irrigation Water Use Calculated From State

Reported Irrigated Acres

Irrigation water use for the 2000 growing season was calculated as the product of the irrigation water requirements (table

9) and reported irrigated crop acres from the OWRB and

TWDB (table 5). An estimated total of 196,026 acre-feet of

water were used for irrigation in the Lake Altus drainage basin

during the 2000 growing season (table 11). Ninety-four percent

of the total irrigation water use in the drainage basin occurred in

Texas. Irrigation water use was greatest in Carson County, with

an estimated 138,180 acre-feet, or 70 percent of the total irrigation water use in the drainage basin (table 11). Gray County

accounted for 16 percent of irrigation water use in the drainage

basin; whereas, Wheeler County accounted for 7 percent of irrigation water use. Irrigation water use for Oklahoma counties

was greatest in Beckham County, with an estimated 5,830 acrefeet, accounting for 3 percent of irrigation water use in the

drainage basin.

 Irrigation water use was greatest for wheat, with an estimated 90,955 acre-feet, or 46 percent of irrigation water use in

the drainage basin (fig. 8). Irrigation water use for corn was

30,329 acre-feet, or 15 percent of the irrigation water use in the

drainage basin. The distribution of irrigation water use for other

crops was 13 percent soybeans, 10 percent sorghum, and 5 percent hay, with alfalfa, cotton, peanuts, and sunflowers making
Irrigation Water Use Calculated From State Reported Irrigated Acres 19

Table 10. Irrigation water use for portion of counties in the Lake Altus drainage basin during the 2000 growing season, calculated from

remotely sensed irrigated acres

[–, not determined]

Counties State

Irrigation water use (acre-feet)

Alfalfa Corn Peanuts Sorghum Soybeans Wheat Total

Beckham Okla. 20,986 – 1,259 – – 4,831 27,076

Greer Okla. 3,826 – 355 – – 858 5,039

Kiowa Okla. 1,538 – 344 – – 629 2,511

Roger Mills Okla. 4,771 – 521 – – 628 5,920

Washita Okla. 129 – 17 – – 14 160

Total Okla. 31,250 – 2,496 – – 6,960 40,706

Carson Tex. 3 10,397 0 3,767 5,426 38,962 58,555

Donley Tex. 0 366 0 2 156 104 628

Gray Tex. 492 5,117 0 304 3,318 22,606 31,837

Randall Tex. 3 2 0 17 103 4,755 4,880

Potter Tex. – –––– ––

Wheeler Tex. 7,263 460 1,073 30 2,183 7,305 18,314

Total Tex. 7,761 16,342 1,073 4,120 11,186 73,732 114,214

Basin Total 39,011 16,342 3,569 4,120 11,186 80,692 154,920

39,011

16,342

11,186

80,692

3,569 4,120

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

Alfalfa Corn Peanuts Sorghum Soybeans Wheat

IRRIGATION WATER USE, IN ACRE-FEET

IRRIGATED CROPS

90,000

100,000

Figure 7. Irrigation water use for crops in the Lake Altus drainage basin during the 2000 growing season, calculated from remotely sense irrigated acres.
20 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Table 11. Irrigation water use for portion of counties in the Lake Altus drainage basin during the 2000 growing season, calculated from irrigated acres reported from Oklahoma Water Resources Board and the Texas Water Development Board

[–, not determined]

Counties State

Irrigation water use (acre-feet)

Alfalfa Corn Cotton Hay Peanuts

SorghumSoybeansSunflowers Wheat Total

Beckham Okla. 1,517 4 23 1,433 2,435 234 – – 184 5,830

Greer Okla. 1,193 0 35 186 1,259 0 – – 86 2,759

Kiowa Okla. 0 764 0 182 246 132 – – 83 1,407

Roger Mills Okla. 238 0 517 310 0 0 – – 0 1,065

Washita Okla. – – – –– – – – – –

Total Okla. 2,948 768 575 2,111 3,940 366 0 0 353 11,061

Carson Tex. 1,755 20,861 1,220 992 0 16,978 18,920 4,386 73,068 138,180

Donley Tex. 79 29 190 68 89 67 17 0 64 603

Gray Tex. 621 8,094 109 1,018 0 1,322 6,156 0 14,628 31,948

Randall Tex. 229 52 38 174 0 62 0 0 393 948

Potter Tex. 3 6 5 4 0 39 0 0 52 109

Wheeler Tex. 0 519 4,148 5,154 841 118 0 0 2,397 13,177

Total Tex. 2,687 29,561 5,710 7,410 930 18,586 25,093 4,386 90,602 184,965

Basin Total 5,635 30,329 6,285 9,521 4,870 18,952 25,093 4,386 90,955 196,026

6,285 9,521

30,329

18,952

90,955

4,386

25,093

5,635 4,870

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

IRRIGATION WATER USE, IN ACRE-FEET

IRRIGATED CROPS

100,000

Alfalfa

Corn

Cotton

Hay

Peanuts

Sorghum

Soybeans

Sunflowers

Wheat

Figure 8. Irrigation water use for crops in the Lake Altus drainage basin during the 2000 growing season, calculated from irrigated acres reported from the Oklahoma Water Resources Board and the Texas Water Development Board.
Comparison of Irrigation Water Use Calculated From Remotely Sensed Irrigated Acres With Irrigation Water Use Calculated From

State Reported Irrigated Acres 21

up the remaining 11 percent of the irrigation water use. Irrigation water use for alfalfa, corn, sorghum, soybeans, sunflowers,

and wheat was greatest in Carson County, Texas; whereas, irrigation water use for cotton and hay was greatest in Wheeler

County, Texas (table 11). Irrigation water use for peanuts was

greatest in Beckham County, Oklahoma.

Comparison of Irrigation Water Use

Calculated From Remotely Sensed Irrigated

Acres With Irrigation Water Use Calculated

From State Reported Irrigated Acres

Estimates of irrigation water use determined from

remotely sensed irrigated acres were different than those

derived from irrigated crop acres reported by the OWRB and

TWDB (figs. 9 and 10). The total volume of water used for irrigation calculated from remotely sensed acres was 154,920 acrefeet (table 10); whereas, irrigation water use calculated using

irrigated acres from the OWRB and TWDB was 196,026 acrefeet (table 11), a 23 percent difference (pd). The percent difference is the preferred method to compare two quantities neither

of which is known to be correct (University of California,

Davis, 2002). Equation 5 was used in this report to calculate

percent differences:

(5)

where

pd = percent difference

A = remotely sensed irrigated acres,

B = the state reported irrigated crop acres from the

OWRB and the TWDB

The greatest difference of estimated irrigation water use

calculated by the two methods was in Carson County, Texas.

Irrigation water use for Carson County calculated from the

remotely sensed irrigated acres was 58,555 acre-feet (table 10);

whereas, irrigation water use calculated from reported irrigated

acres from the TWDB was 138,180 acre-feet (table 11, fig. 8),

an 81 percent difference. The second greatest difference in irrigation water use occurred in Beckham County, Oklahoma. Irrigation water use for Beckham County calculated from the

remotely sensed acres was 27,076 acre-feet; whereas, irrigation

water use calculated from reported irrigated acres from the

OWRB was 5,830 acre-feet, a 129 percent difference.

Irrigation water use for corn, cotton, hay, peanuts, sorghum, soybeans, sunflowers, and wheat calculated from

OWRB and TWDB acres was consistently greater than irrigation water use calculated from remotely sensed irrigated crop

acres (fig. 10). Irrigation water use for alfalfa calculated from

the remotely sensed irrigated crop acres was 39,011 acre-feet

(table 10); whereas, irrigation water use calculated from

reported irrigated crop acres from the OWRB and TWDB was

5,635 acre-feet (table 11), a 150 percent difference (fig. 10).

Most of the large differences in irrigation water use for alfalfa

(19,469 acre-feet) were due to irrigation water use estimates

calculated from remotely sensed irrigated acres of alfalfa in

Beckham County (table 4). Difficulty in determining irrigated

alfalfa probably was caused in part by a very wet spring and

early summer in Oklahoma counties. Another possible reason

for the differences could be caused by alfalfa being harvested

every couple of months. Alfalfa could have been harvested

prior to acquisition of imagery used to map irrigated alfalfa.

Comparing irrigation water use for corn, sorghum, and wheat

calculated from the remotely sensed irrigated crop acres with

those calculated from irrigated crop acres reported by the

OWRB and TWDB, there was a 60 percent difference for corn,

a 129 percent difference for sorghum, and a 77 percent difference for soybeans (fig. 10). Irrigation water use for cotton, hay,

and sunflowers was calculated from the OWRB and TWDB

reported acres (total of 20,192 acre-feet), but could not be calculated from the remotely sensed acres because they were not

successfully identified during the mapping of irrigated acres

from remote sensing techniques and Landsat imagery (tables 10

and 11).

This report provides two estimates of irrigation water use

calculated using the same evapotranspiration model with identical model parameters. Differences between the two irrigation

water use estimates result from differences between the

remotely sensed irrigated acres and irrigated acres reported by

OWRB and the TWDB. Image date selection is vital to accurately determine irrigated crops. Images are taken from the

Landsat ETM+ satellite that rotate back to a specific geographic

location every 16 days. By having to determine irrigated acres

for a specific growing season and having to acquire imagery as

close as possible to maximum greenness for individual crops on

a cloud free day, few images were available that could be used

to determine irrigated crops. For instance, in Carson County,

some harvesting could have occurred just before the date of

image acquisition, which would cause irrigated acres to be

underestimated. Having several months of above average precipitation preceding the date of image acquisition could cause

non-irrigated lands to be classified as irrigated, which would

cause irrigated acres to be overestimated, as in Beckham

County.

Even with correct date selection, limitations to using Landsat multispectral satellite imagery include spectral range and

spatial resolution. Some agricultural crops or vegetation species

are too spectrally similar to be differentiated by Landsat.

Hyperspectral sensors with broader spectral ranges and resolutions may enable greater distinction of vegetation classes. With

multispectral sensors such as Landsat, there are only 5 broad

spectral bands of recorded information; hyperspectral sensors

can range from 36 to 224 spectral bands of recorded information. With an increased spectral range and resolution, it may be

possible to better identify subtle changes in chlorophyll absorption that relate to different vegetation species and health of a

vegetation species.

pd

A B –

A B + ÷ 2 = -------------------------- × 100
22 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season Irrigation Water Use by County

0

80,00060,00040,00020,000

140,000120,000100,000

COUNTY

Irrigation water use calculated from remotely sensed irrigated acres (A)Irrigation water use calculated from irrigated acres from the Oklahoma WaterResources Board and the Texas Water Development Board (B)

0

PERCENT DIFFERENCE, IN PERCENT

Percent difference =

•

20015010050

IRRIGATION WATER USE, IN ACRE-FEET

160,000

Beckham

Greer

Kiowa

Roger Mills

Washita

Carson

Donley

Gray

Potter

Randall

Wheeler

•

•

•

•

•

•

•

•

•

•

•

|A - B|

|A + B|÷2

X 100

Figure 9. Comparison of irrigation water use calculated from remotely sensed irrigated acres with irrigation water use calculated from irrigated acres reported from

the Oklahoma Water Resources Board and Texas Water Development Board in the Lake Altus drainage basin during the 2000 growing season, shown by county,
Comparison of Irrigation Water Use Calculated From Remotely Sensed Irrigated Acres With Irrigation Water Use Calculated From

State Reported Irrigated Acres 23

Irrigation Water Useby Crop

0

90,00080,00070,00060,00050,00040,00030,00020,00010,000

100,000

Irrigation water use calculated from remotely sensed irrigated acres (A)Irrigation water use calculated from irrigated acres from the Oklahoma Water ResourcesBoard and the Texas Water Development Board (B)

IRRIGATION WATER USE, IN ACRE-FEET

IRRIGATED CROPS

200150100500

PERCENT DIFFERENCE, IN PERCENT

Percent difference =

250

Alfalfa

Corn

Cotton

Hay

Peanuts

Sorghum

Soybeans

Sunflowers

Wheat

•

•

•

•

•

•

•

•

•

•

|A - B|

|A + B|÷2

X 100

Figure 10. Comparison of irrigation water use calculated from remotely sensed irrigated crop acres with irrigation water use calculated from irrigated acres reported bythe Oklahoma Water Resources Board and Texas Water Development Board in the Lake Altus drainage basin during the 2000 growing season, shown by crop.
24 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Summary

Increased demand for water in the Lake Altus drainage

basin requires better estimates of water use for irrigation in the

drainage basin. The U.S. Geological Survey, in cooperation

with the Bureau of Reclamation, investigated new techniques to

improve estimates of irrigation water use in the Lake Altus

drainage basin. Empirical estimates of reference evapotranspiration, crop evapotranspiration, and crop irrigation water

requirements for nine major crops were calculated for the 2000

growing season, September 1999 to October 2000 using a solar

radiation-based evapotranspiration model and estimates of irrigated crop acres.

Landsat 7 ETM+ imagery was used to map land use and

irrigated crop acres during the 2000 growing season. Land use

was mapped using a supervised clustering algorithm based on

statistical signatures for 25 pixel classes. Irrigated crop acres

were determined using a ratio vegetation index that consisted of

a near infrared band divided by a visible red band. A total of

78,612 acres were determined to be irrigated. Beckham County

had the greatest number of irrigated crop acres in Oklahoma

counties, followed by Roger Mills, Greer, Kiowa, and Washita.

Carson County had the largest number of irrigated crop acres in

Texas counties, followed by Gray, Wheeler, Potter, and Donley

Counties. Seventy-four percent of the total irrigated crop acreage in the drainage basin occurred in Texas counties. One hundred percent of irrigated corn, sorghum, and soybeans in the

drainage basin occurred in Texas. Eighty-nine percent or

38,677 acres of irrigated wheat occurred in Texas. Eighty-one

percent or 13,768 acres of irrigated alfalfa and 71 percent or

1,583 acres of irrigated peanuts occurred in Oklahoma.

Reported estimates of irrigated crop acres were compiled

and summarized for the 2000 growing season from the OWRB

and TWDB. A total of 98,322 acres were determined to be irrigated. Beckham County had the greatest number of irrigated

crop acres in Oklahoma counties, followed by Greer, Kiowa,

and Roger Mills. Carson County had the greatest number of irrigated crop acres in Texas counties, followed by Gray, Wheeler,

Potter, Donley, and Randall. Ninety-four percent of the total

irrigated crop acres were in Texas counties. One hundred percent of irrigated sunflowers and soybeans, 99 percent of wheat,

98 percent of sorghum and corn, and 91 percent of irrigated cotton in the drainage basin occurred in Texas. Only irrigated

alfalfa and irrigated peanuts had more acreage in Oklahoma

than in Texas.

According to irrigation water use calculated from the

remotely sensed irrigated acres, there was an estimated 154,920

acre-feet of water used for irrigation in the Lake Altus drainage

basin during the 2000 growing season. Seventy-four percent of

the irrigation water use in the drainage basin occurred in Texas

counties. Irrigation water use was greatest for wheat with an

estimated 80,692 acre-feet, or 52 percent of the total irrigation

water use in the drainage basin. Irrigation water use for alfalfa

was 39,011 acre-feet, or 25 percent of the total irrigation water

use. Irrigation water use for corn, sorghum, soybeans, and

wheat was greatest in Carson County, Texas; whereas, most of

the irrigation water use for alfalfa and peanuts occurred in

Beckham County.

According to irrigation water use calculated from the state

reported irrigated acres, there was an estimated 196,026 acrefeet of water used for irrigation in the Lake Altus drainage basin

during the 2000 growing season. Ninety-four percent of the

total irrigation water use occurred in Texas. Irrigation water use

was greatest for wheat with an estimated 90,955 acre-feet, or 46

percent of irrigation water use in the drainage basin. Irrigation

water use for corn was 30,329 acre-feet, or 15 percent of the irrigation water use. Irrigation water use for alfalfa, corn, sorghum, soybeans, sunflowers, and wheat was greatest in Carson

County, Texas; whereas, irrigation water use for cotton and hay

was greatest in Wheeler County, Texas. Irrigation water use for

peanuts was greatest in Beckham County, Oklahoma.

Estimates of irrigation water use calculated from remotely

sensed irrigated acres were different than those determined

from the state reported irrigated acres. The total volume of

water used for irrigation calculated from remotely sensed acres

was 154,920 acre-feet; whereas, irrigation water use calculated

from the state reported irrigated acres was 196,026 acre-feet, a

23 percent difference. Irrigation water use for Carson County

calculated from the remotely sensed acres was 58,555 acre-feet,

whereas, irrigation water use calculated from irrigated crop

acres reported from the state reported irrigated acres was

138,180 acre-feet, an 81 percent difference. Irrigation water use

for alfalfa calculated from the remotely sensed irrigated crop

acres was 39,011 acre-feet; whereas, irrigation water use for

alfalfa calculated from irrigated crop acres reported from the

state reported irrigated acres was 5,635 acre-feet, a 150 percent

difference.

Differences between the two irrigation water use estimates

result from differences between the remotely sensed irrigated

acres and the state reported irrigated acres from the OWRB and

the TWDB. By having to determine irrigated acres for a specific

growing season and having to acquire imagery as close as possible to maximum greenness for individual crops on a cloud free

day, few images are available that could be used to determine

irrigated crops.

Even with correct date selection, limitations to using Landsat multispectral satellite imagery include spectral range and

spatial resolution. Some agricultural crops or vegetation species

are too spectrally similar to be differentiated by Landsat.

Hyperspectral sensors with broader spectral ranges and resolutions may enable greater distinction of vegetation classes. With

an increased spectral range and resolution, it is possible to identify subtle changes in chlorophyll absorption that relate to different vegetation species and health of a vegetation species.

Presently (2002), there are two high spatial-resolution satellites

(IKONOS and QUICKBIRD) with 4-meter multi-spectral sensors.
Selected References 25

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26 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

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Appendixes
28 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season
Appendixes 29

Appendix 1. Remote sensing classification categories shown with number of pixels and acres for the part of Beckham County, Oklahoma, in the Lake Altus drainage basin during the 2000 growing season

[Null, part of the image that is outside the portion of the drainage basin in the county]

Class name Code Pixels Acres Percent image

Urban 1 9,883 1,984 0

Water 2 5,282 1,060 0

Clouds 3 235 47 0

Fallow 4 66,745 13,396 2

Grass 5 941,516 188,973 33

Trees 6 164,691 33,055 6

Sunflowers 7 0 0 0

Oat 8 46 9 0

Peanuts 9 21,111 4,237 1

Soybeans 10 0 0 0

Rye 11 4,612 926 0

Cotton 12 1,757 353 0

Sorghum 13 28 6 0

Alfalfa 14 93,383 18,743 3

Corn 15 0 0 0

Wheat 16 213,310 42,814 7

Unknown irrigated crop 17 48,758 9,786 2

Irrigated soybeans 18 1 0 0

Irrigated peanuts 19 4,021 807 0

Cowpeas 20 16,065 3,224 1

Unknown crop 21 7,815 1,569 0

Irrigated alfalfa 22 46,320 9,297 2

Irrigated wheat 23 17,390 3,490 1

Hay/Pasture 24 157,108 31,533 5

Irrigated corn 25 0 0 0

Irrigated sorghum 26 0 0 0

Null 0 1,076,588 216,083 37

Image total 2,896,665 581,393 100
30 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Appendix 2. Remote sensing classification categories shown with number of pixels and acres for the part of Carson County, Texas, in the

Lake Altus drainage basin during the 2000 growing season

[Null, part of the image that is outside the portion of the drainage basin in the county]

Class name Code Pixels Acres Percent image

Urban 1 37,910 7,609 1

Water 2 15,312 3,073 1

Clouds 3 2,044 410 0

Fallow 4 209,717 42,093 7

Grass 5 274,841 55,164 9

Trees 6 198 40 0

Sunflowers 7 23,985 4,814 1

Oat 8 0 0 0

Peanuts 9 0 0 0

Soybeans 10 6,334 1,271 0

Rye 11 13,104 2,630 0

Cotton 12 22 4 0

Sorghum 13 61,544 12,353 2

Alfalfa 14 0 0 0

Corn 15 31 6 0

Wheat 16 294,222 59,054 10

Unknown irrigated crop 17 40,672 8,163 1

Irrigated soybeans 18 11,756 2,360 0

Irrigated peanuts 19 0 0 0

Cowpeas 20 0 0 0

Unknown crop 21 2,881 578 0

Irrigated alfalfa 22 4 1 0

Irrigated wheat 23 97,904 19,650 3

Hay/Pasture 24 189,949 38,125 6

Irrigated corn 25 27,766 5,573 1

Irrigated sorghum 26 9,451 1,897 0

Null 0 1,625,226 326,201 55

Image total 2,944,873 591,069 100
Appendixes 31

Appendix 3. Remote sensing classification categories shown with number of pixels and acres for the part of Donley County, Texas, in the

Lake Altus drainage basin during the 2000 growing season

[Null, part of the image that is outside the portion of the drainage basin in the county]

Class name Code Pixels Acres Percent image

Urban 1 276 55 0

Water 2 501 101 0

Clouds 3 0 0 0

Fallow 4 1,800 361 0

Grass 5 20,358 4,086 1

Trees 6 0 0 0

Sunflowers 7 232 47 0

Oat 8 0 0 0

Peanuts 9 0 0 0

Soybeans 10 0 0 0

Rye 11 0 0 0

Cotton 12 9 2 0

Sorghum 13 2,136 429 0

Alfalfa 14 0 0 0

Corn 15 0 0 0

Wheat 16 3,662 735 0

Unknown irrigated crop 17 2,512 504 0

Irrigated soybeans 18 328 66 0

Irrigated peanuts 19 0 0 0

Cowpeas 20 0 0 0

Unknown crop 21 0 0 0

Irrigated alfalfa 22 0 0 0

Irrigated wheat 23 273 55 0

Hay/Pasture 24 2,293 460 0

Irrigated corn 25 994 200 0

Irrigated sorghum 26 5 1 0

Null 0 2,746,372 551,228 99

Image total 2,781,751 558,329 100
32 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Appendix 4. Remote sensing classification categories shown with number of pixels and acres for the part of Gray County, Texas, in the

Lake Altus drainage basin during the 2000 growing season

[Null, part of the image that is outside the portion of the drainage basin in the county]

Class name Code Pixels Acres Percent image

Urban 1 13,205 2,650 0

Water 2 31,256 6,273 1

Clouds 3 1,734 348 0

Fallow 4 89,254 17,914 3

Grass 5 1,761,917 353,637 59

Trees 6 43,566 8,744 1

Sunflowers 7 13,629 2,736 0

Oat 8 0 0 0

Peanuts 9 0 0 0

Soybeans 10 9,104 1,827 0

Rye 11 12,936 2,596 0

Cotton 12 3 1 0

Sorghum 13 37,820 7,591 1

Alfalfa 14 0 0 0

Corn 15 859 172 0

Wheat 16 143,573 28,817 5

Unknown irrigated crop 17 8,918 1,790 0

Irrigated soybeans 18 7,008 1,407 0

Irrigated peanuts 19 0 0 0

Cowpeas 20 0 0 0

Unknown crop 21 0 0 0

Irrigated alfalfa 22 934 187 0

Irrigated wheat 23 59,719 11,986 2

Hay/Pasture 24 99,635 19,998 3

Irrigated corn 25 13,910 2,792 0

Irrigated sorghum 26 743 149 0

Null 0 617,894 124,018 21

Image total 2,967,617 595,634 100
Appendixes 33

Appendix 5. Remote sensing classification categories shown with number of pixels and acres for the part of Greer County, Oklahoma, in

the Lake Altus drainage basin during the 2000 growing season

[Null, part of the image that is outside the portion of the drainage basin in the county]

Class name Code Pixels Acres Percent image

Urban 1 487 98 0

Water 2 15,429 3,097 1

Clouds 3 0 0 0

Fallow 4 13,089 2,627 1

Grass 5 63,475 12,740 4

Trees 6 20,409 4,096 1

Sunflowers 7 0 0 0

Oat 8 29 6 0

Peanuts 9 2,504 503 0

Soybeans 10 0 0 0

Rye 11 1,257 252 0

Cotton 12 21 4 0

Sorghum 13 6 1 0

Alfalfa 14 12,847 2,579 1

Corn 15 0 0 0

Wheat 16 36,735 7,373 2

Unknown irrigated crop 17 4,764 956 0

Irrigated soybeans 18 0 0 0

Irrigated peanuts 19 1,119 225 0

Cowpeas 20 3,942 791 0

Unknown crop 21 4,906 985 0

Irrigated alfalfa 22 8,564 1,719 1

Irrigated wheat 23 2,985 599 0

Hay/Pasture 24 45,017 9,035 3

Irrigated corn 25 0 0 0

Irrigated sorghum 26 0 0 0

Null 0 1,454,766 291,988 86

Image total 1,692,351 339,674 100
34 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Appendix 6. Remote sensing classification categories shown with number of pixels and acres for the part of Kiowa County, Oklahoma, in

the Lake Altus drainage basin during the 2000 growing season

[Null, part of the image that is outside the portion of the drainage basin in the county]

Class name Code Pixels Acres Percent image

Urban 1 103 21 0

Water 2 15,089 3,029 3

Clouds 3 26 5 0

Fallow 4 8,592 1,725 1

Grass 5 33,530 6,730 6

Trees 6 11,653 2,339 2

Sunflowers 7 0 0 0

Oat 8 0 0 0

Peanuts 9 1,383 278 0

Soybeans 10 0 0 0

Rye 11 96 19 0

Cotton 12 384 77 0

Sorghum 13 4 1 0

Alfalfa 14 4,817 967 1

Corn 15 0 0 0

Wheat 16 53,878 10,814 9

Unknown irrigated crop 17 6,261 1,257 1

Irrigated soybeans 18 0 0 0

Irrigated peanuts 19 1,086 218 0

Cowpeas 20 2,803 563 0

Unknown crop 21 3,933 789 1

Irrigated alfalfa 22 3,443 691 1

Irrigated wheat 23 2,193 440 0

Hay/Pasture 24 12,069 2,422 2

Irrigated corn 25 0 0 0

Irrigated sorghum 26 0 0 0

Null 0 425,050 85,312 72

Image total 586,393 117,696 100
Appendixes 35

Appendix 7. Remote sensing classification categories shown with number of pixels and acres for the part of Potter County, Texas, in the

Lake Altus drainage basin during the 2000 growing season

[Null, part of the image that is outside the portion of the drainage basin in the county]

Class name Code Pixels Acres Percent image

Urban 1 31,399 6,302 3

Water 2 2,738 550 0

Clouds 3 1,007 202 0

Fallow 4 36,225 7,271 3

Grass 5 52,846 10,607 4

Trees 6 25 5 0

Sunflowers 7 599 120 0

Oat 8 0 0 0

Peanuts 9 0 0 0

Soybeans 10 619 124 0

Rye 11 698 140 0

Cotton 12 6 1 0

Sorghum 13 5,127 1,029 0

Alfalfa 14 0 0 0

Corn 15 0 0 0

Wheat 16 39,696 7,967 3

Unknown irrigated crop 17 380 76 0

Irrigated soybeans 18 209 42 0

Irrigated peanuts 19 0 0 0

Cowpeas 20 0 0 0

Unknown crop 21 0 0 0

Irrigated alfalfa 22 5 1 0

Irrigated wheat 23 11,153 2,239 1

Hay/Pasture 24 17,034 3,419 1

Irrigated corn 25 5 1 0

Irrigated sorghum 26 37 7 0

Null 0 1,035,745 207,886 84

Image total 1,235,553 247,990 100
36 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Appendix 8. Remote sensing classification categories shown with number of pixels and acres for the part of Roger Mills County, Oklahoma, in the Lake Altus drainage basin during the 2000 growing season

[Null, part of the image that is outside the portion of the drainage basin in the county]

Class name Code Pixels Acres Percent image

Urban 1 446 90 0

Water 2 2,372 476 0

Clouds 3 5 1 0

Fallow 4 46,842 9,402 2

Grass 5 267,012 53,592 13

Trees 6 21,000 4,215 1

Sunflowers 7 0 0 0

Oat 9 0 0 0

Peanuts 9 6,322 1,269 0

Soybeans 10 0 0 0

Rye 11 6 1 0

Cotton 12 2,436 489 0

Sorghum 13 8 2 0

Alfalfa 14 30,045 6,030 1

Corn 15 0 0 0

Wheat 16 35,067 7,038 2

Unknown irrigated crop 17 10,348 2,077 1

Irrigated soybeans 18 2 0 0

Irrigated peanuts 19 1,567 315 0

Cowpeas 20 326 65 0

Unknown crop 21 1,623 326 0

Irrigated alfalfa 22 9,978 2,003 0

Irrigated wheat 23 2,343 470 0

Hay/Pasture 24 34,260 6,876 2

Irrigated corn 25 0 0 0

Irrigated sorghum 26 0 0 0

Null 0 1,573,612 315,842 77

Image total 2,045,620 410,579 100
Appendixes 37

Appendix 9. Remote sensing classification categories shown with number of pixels and acres for the part of Washita County, Oklahoma,

in the Lake Altus drainage basin during the 2000 growing season

[Null, part of the image that is outside the portion of the drainage basin in the county]

Class name Code Pixels Acres Percent image

Urban 1 0 0 0

Water 2 0 0 0

Clouds 3 0 0 0

Fallow 4 21 4 0

Grass 5 4,421 887 1

Trees 6 0 0 0

Sunflowers 7 0 0 0

Oat 8 2 0 0

Peanuts 9 474 95 0

Soybeans 10 0 0 0

Rye 11 2 0 0

Cotton 12 124 25 0

Sorghum 13 0 0 0

Alfalfa 14 115 23 0

Corn 15 0 0 0

Wheat 16 3,034 609 0

Unknown irrigated crop 17 190 38 0

Irrigated soybeans 18 0 0 0

Irrigated peanuts 19 57 11 0

Cowpeas 20 3,356 674 0

Unknown crop 21 4 1 0

Irrigated alfalfa 22 289 58 0

Irrigated wheat 23 49 10 0

Hay/Pasture 24 575 115 0

Irrigated corn 25 0 0 0

Irrigated sorghum 26 0 0 0

Null 0 809,145 162,405 98

Image total 821,858 164,956 100
38 Comparison of Irrigation Water Use Estimates Calculated From Remotely Sensed Irrigated Acres and State Reported Irrigated Acres in the Lake Altus Drainage Basin, Oklahoma and Texas, 2000 Growing Season

Appendix 10. Remote sensing classification categories shown with number of pixels and acres for the part of Wheeler County, Texas, in

the Lake Altus drainage basin during the 2000 growing season

[Null, part of the image that is outside the portion of the drainage basin in the county]

Class name Code Pixels Acres Percent image

Urban 1 16,772 3,366 1

Water 2 5,001 1,004 0

Clouds 3 49,108 9,857 2

Fallow 4 77,356 15,526 3

Grass 5 1,390,894 279,168 48

Trees 6 430,251 86,356 15

Sunflowers 7 94 19 0

Oat 8 4 1 0

Peanuts 9 5,195 1,043 0

Soybeans 10 8,107 1,627 0

Rye 11 2,144 430 0

Cotton 12 459 92 0

Sorghum 13 47,654 9,565 2

Alfalfa 14 35,649 7,155 1

Corn 15 132 26 0

Wheat 16 103,652 20,804 4

Unknown irrigated crop 17 26,993 5,418 1

Irrigated soybeans 18 4,795 962 0

Irrigated peanuts 19 3,221 646 0

Cowpeas 20 2,681 538 0

Unknown crop 21 8,827 1,772 0

Irrigated alfalfa 22 14,956 3,002 1

Irrigated wheat 23 23,653 4,747 1

Hay/Pasture 24 70,080 14,066 2

Irrigated corn 25 1,325 266 0

Irrigated sorghum 26 75 15 0

Null 0 577,827 115,976 20

Image total 2,906,905 583,449 100
Appendixes 39