Analysis of Water Use Trends in the

United States: 1950-1995

FINAL PROJECT COMPLETION REPORT

Prepared for:

1999 USGS National Competitive Grants Program

Grant No. 99HQGR0222

Subgrant No. 00-312

United States Geological Survey

Reston, Virginia 20192

Prepared by:

Ben Dziegielewski, Professor, Department of Geography

Subhash C. Sharma, Professor, Department of Economics

Thomas J. Bik, Researcher, Department of Geography

Heru Margono, Graduate Assistant, Department of Economics

Xiaoying Yang, Graduate Assistant, Department of Geography

Southern Illinois University at Carbondale

Carbondale, IL 62901-4514

February 28, 2002

Page

Table of Contents............................................................................................................. ii

List of Tables................................................................................................................... x

List of Figures................................................................................................................ xx

Acknowledgement........................................................................................................ xxii

EXECUTIVE SUMMARY

Study Purpose............................................................................................... ES-1

Data and Methods......................................................................................... ES-1

National and State Trends.............................................................................. ES-2

Demand Drivers and Intensity of Use............................................................. ES-3

Determinants of Changes in Per Unit Use....................................................... ES-4

Structure of Water Use Models..................................................................... ES-6

Accuracy of State-level Predictions................................................................ ES-7

County-level Data and Models....................................................................... ES-8

Recommendations......................................................................................... ES-9

1. INTRODUCTION

Purpose of the Study........................................................................................ 1-1

Background of the NWUIP.............................................................................. 1-2

Setting the Framework: 1950 - 1960................................................................ 1-3

USGS Circular 115 ................................................................................... 1-3

USGS Circular 398 ................................................................................... 1-3

USGS Circular 456 ................................................................................... 1-4

Increasing Disaggregation and Explanation: 1965 - 1975................................... 1-4

USGS Circular 556 ................................................................................... 1-4

USGS Circular 676 ................................................................................... 1-6

USGS Circular 765 ................................................................................... 1-6

Federation Support and Implementation of the NWUIP: 1980 - 1995............... 1-7

USGS Circular 1001 ................................................................................. 1-7

USGS Circular 1004 ................................................................................. 1-9

USGS Circular 1081 ............................................................................... 1-10

USGS Circular 1200 ............................................................................... 1-10

Overview and Implications of the Water Use Inventory Data and Process....... 1-11

Chapter Synopsis........................................................................................... 1-12

References..................................................................................................... 1-14

2. STUDY APPROACH

Purpose........................................................................................................... 2-1

Modeling Framework ...................................................................................... 2-1

Data Structure............................................................................................ 2-1

Model Specification .................................................................................. 2-2

Dependent Variables........................................................................................ 2-3

Data Sources and Acquisition..................................................................... 2-3

Spatial Coverage........................................................................................ 2-3

Period of Analysis...................................................................................... 2-3

Sectoral Coverage..................................................................................... 2-4

Independent Variables...................................................................................... 2-5

Data Sources and Acquisition..................................................................... 2-5

Period of Analysis...................................................................................... 2-6

Categories of Independent Variables.......................................................... 2-6

Data Interpolation and Standardization Procedures..................................... 2-7

Data Validation Procedures.............................................................................. 2-8

Verification from USGS State Water Use Coordinators.............................. 2-9

Assessment of Overall Accuracy.......................................................... 2-9

Thermoelectric Accuracy Email Survey................................................. 2-9

Adjusting Weather Data to Correspond with Data Collection Years...... 2-9

Estimation and Diagnostic Procedures............................................................. 2-10

Modeling Approach................................................................................. 2-10

Modeling Diagnostic and Validation Procedures........................................ 2-11

Accuracy of Predictions................................................................................. 2-11

3. LONG-TERM NATIONAL TRENDS

Purpose........................................................................................................... 3-1

Trends in Total Withdrawals............................................................................. 3-1

Changes in Sectoral Withdrawals...................................................................... 3-3

Domestic Withdrawals............................................................................... 3-4

Industrial Withdrawals ............................................................................... 3-6

Irrigation Withdrawals ............................................................................... 3-8

Thermoelectric Withdrawals .................................................................... 3-10

Trends in Withdrawals by Source of Water..................................................... 3-13

Total Withdrawals.................................................................................... 3-13

Public Supply and Rural Domestic Withdrawals ....................................... 3-15

Industrial Withdrawals.............................................................................. 3-15

Irrigation Withdrawals.............................................................................. 3-16

Thermoelectric Withdrawals..................................................................... 3-17

Summary....................................................................................................... 3-18

References..................................................................................................... 3-19

4. STATE CONTRIBUTIONS TO NATIONAL TRENDS

Purpose........................................................................................................... 4-1

Trends in Total Withdrawals............................................................................. 4-1

Total Withdrawals and Associated Factors: 1995....................................... 4-2

Trends in Total Withdrawals and Associated Factors: 1960 - 1995............. 4-5

Trends in Total Withdrawals and Associated Factors: 1980 - 1995............. 4-7

Summary of Trends in Total State Withdrawals ........................................ 4-10

Trends in Public Supply and Rural Withdrawals.............................................. 4-10

Public-Supply and Rural Domestic Withdrawals and
Associated Factors: 1995................................................................... 4-10

Trends in Public Supply and Rural Domestic Withdrawals: 1960 - 1995.... 4-12

Trends in Public Supply and Rural Domestic Withdrawals: 1980 - 1995.... 4-13

Trends in State Population and Population Served by Public Supplies.. 4-14

Trends in Median Family Income........................................................ 4-16

Summary of Trends in Public Supply Withdrawals .................................... 4-16

Trends in Self-Supplied Industrial Withdrawals............................................... 4-16

Distribution of Self-Supplied Industrial Withdrawals: 1995........................ 4-17

Trends in Self-Supplied Industrial Withdrawals: 1960 - 1995.................... 4-19

Trends in Self-Supplied Industrial Withdrawals: 1980 - 1995.................... 4-19

Trends in Manufacturing and Mining Employment: 1960 - 1995................ 4-21

Summary of Trends in Self-Supplied Industrial Withdrawals...................... 4-24

Trends in Irrigation Withdrawals..................................................................... 4-25

Irrigation Withdrawals and Associated Factors: 1995................................ 4-25

Trends in Irrigation Withdrawals and Associated Factors: 1950 - 1995..... 4-28

Trends in Irrigation Withdrawals and Associated Factors: 1980 - 1995..... 4-29

Summary of Trends in Irrigation Withdrawals............................................ 4-33

Trends in Thermoelectric Withdrawals............................................................ 4-34

Distribution of Thermoelectric Withdrawals: 1995..................................... 4-34

Trends in Thermoelectric Withdrawals and Associated Factors:
1960 - 1980...................................................................................... 4-36

Trends in Thermoelectric Withdrawals and Associated Factors:
1980 - 1995...................................................................................... 4-38

Summary of Trends in Thermoelectric Withdrawals................................... 4-39

Chapter 4 Annex............................................................................................ 4-41

References..................................................................................................... 4-42

5. EXPLANATORY ANALYSIS OF HISTORICAL WITHDRAWALS

Purpose........................................................................................................... 5-1

Variability of Historical Withdrawals................................................................. 5-1

Total State Withdrawals .................................................................................. 5-2

Exploratory Regressions............................................................................. 5-3

Effects of Extensive (Driver) Variables........................................................ 5-5

Components of Change in Historical Withdrawals....................................... 5-8

Public Supply Withdrawals............................................................................. 5-11

Descriptive Statistics................................................................................ 5-11

Major Demand Drivers............................................................................ 5-11

Total State Population ....................................................................... 5-12

Population Served by Public Systems ................................................ 5-16

Components of Change in Historical Withdrawals .................................... 5-18

Multiple Regression Models of Total Public Supply Withdrawals .............. 5-20

Linear Model..................................................................................... 5-20

Log-Linear Model ............................................................................. 5-22

Multiple Regression Models of Per Capita Public Supply Withdrawals...... 5-24

Self-Supplied Industrial Withdrawal................................................................ 5-29

Descriptive Statistics................................................................................ 5-29

Major Demand Drivers............................................................................ 5-30

Total State Population........................................................................ 5-30

Industrial (Manufacturing and Mining) Employment............................. 5-32

Components of Change in Historical Withdrawals .................................... 5-33

Multiple Regression Models of Self-supplied Industrial Withdrawals ......... 5-34

Linear Model..................................................................................... 5-34

Log-Linear Model.............................................................................. 5-35

Multiple Regressions of Per Capita and Per Employee Withdrawals ......... 5-36

Per Capita Model of Industrial Withdrawals........................................ 5-37

Per Employee Model of Industrial Withdrawals................................... 5-37

Predictions of National Industrial Withdrawals and Changes ..................... 5-38

Irrigation Withdrawals ................................................................................... 5-40

Descriptive Statistics................................................................................ 5-40

Major Demand Drivers............................................................................ 5-41

Components of Change in Historical Withdrawals .................................... 5-42

Multiple Regression Models of Total Irrigation Withdrawals...................... 5-44

Multiple Regression Models of Per Unit Irrigation Withdrawals................. 5-46

Predictions of National Irrigation Withdrawals and Changes ..................... 5-47

Thermoelectric Withdrawals .......................................................................... 5-51

Descriptive Statistics................................................................................ 5-51

Major Demand Drivers............................................................................ 5-52

Components of Change in Historical Withdrawals .................................... 5-54

Multiple Regression Models of Total Thermoelectric Withdrawals ............ 5-55

Multiple Regression Models of Unit Thermoelectric Withdrawals .............. 5-57

Predictions of National Thermoelectric Withdrawals and Changes ............ 5-60

Chapter 5 Annex...................................................................................... 5-63

6. REGRESSION MODELS FOR PREDICTING AGGREGATE STATE WATER USE

Purpose........................................................................................................... 6-1

Desired Model Accuracy................................................................................. 6-2

Procedure for Developing “Predictive” Regression Models................................ 6-2

Regressions of Public-Supply Withdrawals....................................................... 6-4

Models of Total Public-Supply Withdrawals............................................... 6-5

Linear Regressions............................................................................... 6-5

Log-Linear Regressions ....................................................................... 6-9

Per Capita Withdrawal Models................................................................ 6-15

Linear Per Capita Models.................................................................. 6-15

Log-Linear Per Capita Models .......................................................... 6-19

Comparison of the Estimated Regression Models...................................... 6-23

Regressions of Industrial Water Use .............................................................. 6-23

Total Manufacturing Use Models.............................................................. 6-24

Linear Regressions............................................................................. 6-24

Log-Linear Regressions ..................................................................... 6-25

Per Employee Manufacturing Use Models................................................ 6-27

Linear Regressions of Per Employee Use............................................ 6-28

Log-Linear Regressions of Per Employee Use.................................... 6-29

Comparison of the Estimated Regression Models...................................... 6-34

Allocation of Manufacturing Use to Self-supplied and Public-supplied....... 6-34

Models of Irrigation Withdrawals ................................................................... 6-36

Models of Total Irrigation Withdrawals..................................................... 6-36

Models of Gross Irrigation Rate in Inches Per Year .................................. 6-39

Linear Models of Irrigation Depth....................................................... 6-39

Log-linear Models of Application Depth............................................. 6-41

Regional (East and West) Models of Irrigation Depth.......................... 6-43

Comparison of the Estimated Regression Models...................................... 6-44

Models of Thermoelectric Withdrawals........................................................... 6-45

Total Thermoelectric Withdrawal Models................................................. 6-46

Regressions of Per Unit Withdrawals ....................................................... 6-49

Linear Regressions of Per Unit Withdrawals........................................ 6-49

Log-Linear Regressions of Per Unit Withdrawals................................ 6-51

Comparison of the Estimated Regression Models...................................... 6-54

Models for Other Water-Use Categories........................................................ 6-55

Self-Supplied Domestic Use..................................................................... 6-55

Mining Withdrawals ................................................................................ 6-57

Total Mining Withdrawal Models........................................................ 6-57

Per Employee Mining Withdrawal Models.......................................... 6-60

Livestock Withdrawals ............................................................................ 6-63

References..................................................................................................... 6-65

Chapter 6 Annex............................................................................................ 6-66

7. BACKWARD AND FORWARD PREDICTIONS OF STATE WITHDRAWALS

Purpose........................................................................................................... 7-1

Definitions and Calculations of Forecast Error................................................... 7-1

Sources of Forecast Error.......................................................................... 7-2

The Forecast Error Variance...................................................................... 7-3

Error in a Univariate Regression Model................................................. 7-3

Error in a Multivariate Regression Model.............................................. 7-4

Forecast Error in Multiplicative Models................................................ 7-5

Variance of Total Withdrawals............................................................. 7-6

Trend-Reference Forecast.......................................................................... 7-6

Forecasts of Public-Supply Withdrawals........................................................... 7-7

Backcasts of Per Capita Withdrawals for 1980........................................... 7-7

Forecasts of Per Capita Withdrawals for 2000......................................... 7-10

Forecasts of Manufacturing Use..................................................................... 7-11

Backcasts of Per Employee Manufacturing Use for 1980.......................... 7-11

Forecasts of Per Employee Manufacturing Use for 2000........................... 7-14

Forecasts of Irrigation Withdrawals................................................................ 7-15

Backcasts of Irrigation Depth for 1980..................................................... 7-16

Forecasts of Irrigation Depth for 2000...................................................... 7-19

Forecasts of Withdrawals for Thermoelectric Power....................................... 7-20

Backcasts of Unit Thermoelectric Withdrawals for 1980........................... 7-21

Forecasts of Unit Thermoelectric Withdrawals for 2000............................ 7-23

Supplemental Forecasts.................................................................................. 7-24

Self-Supplied Domestic Use..................................................................... 7-24

Mining Withdrawals................................................................................. 7-27

Livestock Withdrawals............................................................................. 7-28

Forecasts of Total Withdrawals...................................................................... 7-30

Summary....................................................................................................... 7-31

References..................................................................................................... 7-31

Chapter 7 Annex............................................................................................ 7-32

8. ANALYSIS OF COUNTY-LEVEL WATER USE DATA

Purpose........................................................................................................... 8-1

Public-Supply Use........................................................................................... 8-1

Definition of Dependent Variable................................................................ 8-1

Total Public-Supply Deliveries.................................................................... 8-3

Distribution of Dependent Variable Values............................................ 8-3

Withdrawals and Deliveries versus Population Served........................... 8-4

Regressions of Total Public-Supply Deliveries ...................................... 8-6

Per Capita (Net) Public Supply Deliveries................................................... 8-8

Linear Models...................................................................................... 8-9

Log-Linear Models ........................................................................... 8-11

Summary................................................................................................. 8-14

Manufacturing Water Use............................................................................... 8-14

County-level Total Manufacturing Use...................................................... 8-14

Models of Per Employee Manufacturing Use............................................ 8-17

Summary................................................................................................. 8-21

Irrigation Withdrawals.................................................................................... 8-21

County-level Total Irrigation Withdrawals................................................. 8-21

Models of Irrigation Depth....................................................................... 8-27

Models for Counties in Eastern States ................................................ 8-28

Models for Counties in Western States .............................................. 8-30

Summary................................................................................................. 8-33

Chapter 8 Annex............................................................................................ 8-34

9. ANALYSIS OF COUNTY-LEVEL WATER USE BY STATE

Purpose........................................................................................................... 9-1

Estimation Method........................................................................................... 9-1

Public-Supply Use........................................................................................... 9-2

Comparison of National and State-specific Results...................................... 9-2

Descriptive Statistics............................................................................ 9-2

Linear Regressions of Per Capita Deliveries.......................................... 9-4

Log-Linear Regressions of Per Capita Deliveries................................... 9-6

Accuracy of In-sample Predictions ...................................................... 9-7

Manufacturing Use........................................................................................... 9-9

Comparison of National and State-specific Results...................................... 9-9

Descriptive Statistics............................................................................ 9-9

Linear Regressions of Per Employee Uses.......................................... 9-11

Log-Linear Regressions of Per Employee Uses................................... 9-12

Accuracy of In-sample Predictions .................................................... 9-14

Irrigation Withdrawals.................................................................................... 9-16

Comparison of National and State-specific Results.................................... 9-16

Descriptive Statistics.......................................................................... 9-16

Linear Regressions of Gross Irrigation Depth...................................... 9-16

Log-Linear Regressions of Gross Irrigation Depth............................... 9-21

Accuracy of In-sample Predictions .................................................... 9-23

Summary....................................................................................................... 9-25

Chapter 9 Annex............................................................................................ 9-26

County Level Models for Arkansas.......................................................... 9-26

Public Supply Use.............................................................................. 9-26

Manufacturing Use............................................................................. 9-28

Irrigation Withdrawals........................................................................ 9-30

County Level Models for Kansas............................................................. 9-32

Public Supply Use.............................................................................. 9-32

Manufacturing Use............................................................................. 9-34

Irrigation Withdrawals........................................................................ 9-36

County Level Models for Oregon............................................................. 9-38

Public Supply Use.............................................................................. 9-38

Manufacturing Use............................................................................. 9-40

Irrigation Withdrawals........................................................................ 9-41

County Level Models for North Carolina.................................................. 9-42

Public Supply Use.............................................................................. 9-42

Manufacturing Use............................................................................. 9-44

Irrigation Withdrawals........................................................................ 9-46

10. CONCLUSIONS AND RECOMMENDATIONS

Synopsis........................................................................................................ 10-1

Principal Findings........................................................................................... 10-1

Recommendations for Further Research.......................................................... 10-4

Summary....................................................................................................... 10-5

APPENDIX A

State Level Variables....................................................................................... A-2

Description of Public Supply Variables....................................................... A-2

Description of Industrial Variables.............................................................. A-6

Description of Irrigation Variables............................................................ A-11

Description of Thermoelectric Variables................................................... A-14

County Level Variable Definitions and Data Tables........................................ A-19

Description of Public Supply Variables..................................................... A-19

Description of Industrial Variables............................................................ A-22

Description of Irrigation Variables............................................................ A-25

APPENDIX B. CONSULTATIONS WITH USGS STAFF

Purpose........................................................................................................... B-1

General Accuracy Assessment......................................................................... B-2

Introduction............................................................................................... B-2

Response.................................................................................................. B-2

Accuracy of Specific Thermoelectric Withdrawal Data..................................... B-6

Introduction............................................................................................... B-6

Response.................................................................................................. B-6

Alignment of Weather Data to Water Withdrawal Data Collection Time Frames B-8

Introduction............................................................................................... B-8

Response.................................................................................................. B-8

LIST OF TABLES

ES.1 Components of the 1950-1995 Changes in Sectoral Withdrawals................... ES-3

ES.2 Effects of Historical Changes in Explanatory Variables on Per Unit Water
Withdrawals at State Level: from Log-Linear Regression Models............ ES-5

ES.3 Elasticities of Key Explanatory Variables in Log-Linear Regression Models.... ES-6

ES.4 Accuracy of In-sample (1985-1995) and Out-of-sample (1980)
Predictions of State Total Withdrawals .................................................. ES-7

ES.5 Comparison of 1995 Estimates and 2000 Predictions..................................... ES-8

ES.6 In-sample Prediction Errors of Log-Linear County-Level Models .................. ES-8

2.1 General Categories of Explanatory Variables.................................................... 2-7

3.1 Total Water Withdrawals and Demographic and Economic Variables................ 3-2

3.2 Changes in Sectoral Withdrawals ..................................................................... 3-4

3.3 Population and Domestic Withdrawals ............................................................. 3-4

3.4 Domestic Withdrawals and Medial Family Income ........................................... 3-5

3.5 Self -Supplied Industrial Withdrawals and Manufacturing Employment .............. 3-7

3.6 Total Irrigation Withdrawals and Irrigated Acres .............................................. 3-9

3.7 Self-Supplied Thermoelectric Withdrawals and Production ............................. 3-11

3.8 Thermoelectric Generation from Different Sources ......................................... 3-13

3.9 Total and Percent of Withdrawals by Source: 1950-1995 .............................. 3-14

3.10 Groundwater and Surface Water Withdrawals in Public Supply and
Rural Domestic Sectors ......................................................................... 3-15

3.11 Self-Supplied Industrial Withdrawals by Source ............................................. 3-16

3.12 Irrigation Withdrawals by Source ................................................................... 3-17

3.13 Thermoelectric Withdrawals by Source........................................................... 3-17

3.14 Summary of Component Trends and Likely Causes ....................................... 3-18

4.1 Ranking of 1995 State Water Withdrawals by Water-Use Sector,
Top Ten States......................................................................................... 4-2

4.2 Percent Shares of Withdrawal and Associated Demographic and Economic

Measures the Ten States with the Largest Withdrawals ............................ 4-4

4.3 Changes in Manufacturing and Mining Employment and Industrial Withdrawals
(Selected States): 1980-1995................................................................. 4-21

4.4 Employment in Total Manufacturing and Water-Intensive SIC Categories,
1950-1995 ............................................................................................ 4-22

4.5 Employment in Water-Intensive SIC Categories
(Selected States): 1980-1995................................................................. 4-23

4.6 States Reporting More than 20,000 Mining Employees in 1995:
Employees, Withdrawals and Per Employee Withdrawals ....................... 4-24

4.7 Distribution of Irrigation Withdrawals, Acres, Annual Application and
Estimated Pumping Costs (Selected States): 1995 .................................. 4-27

4.8 Changes in Irrigation Withdrawals in Selected States:
1960-1995 and 1980-1995.................................................................... 4-30

4.9 Changes in Irrigated Acreage, Withdrawals, and Application Rate:
1980-1995............................................................................................. 4-32

4.10 Energy Pumping Costs (1995$/ac) for Selected States, 1980–1995,
Ranked by 1995 Costs........................................................................... 4-33

4.11 Thermoelectric Withdrawals, Population, and Gross State Product
in the 20 States with the Largest Thermoelectric Withdrawals, 1995 ....... 4-34

4.12 Changes in Thermoelectric Withdrawals versus Changes in Potential
Explanatory Factors in the States with the Largest Changes in Withdrawals,
1960 to 1980........................................................................................ 4-38

4.13 Changes in Thermoelectric Withdrawals versus Changes in Potential
Explanatory Factors in the States with the Largest Changes in Withdrawals,
1980 to 1995......................................................................................... 4-39

4A.1 Values of Total State Withdrawals and Associated Factors, 1995................... 4-41

5.1 Descriptive Statistics of USGS Estimates of Total and Sectoral Withdrawals:
1950-1995............................................................................................... 5-2

5.2 Descriptive Statistics of Total Withdrawals (mgd) by Year: 1950-1995............. 5-2

5.3 Regression of Total State Withdrawals: 1950-1995.......................................... 5-4

5.4 Regression of Total Water Withdrawals on Demand Drivers: 1950-1995.......... 5-5

5.5 Regression of Total Withdrawal on Demand Drivers: Parameter Estimates
for Each Data Year .................................................................................. 5-7

5.6 Linear Regression of Total Withdrawals: 1950-1975 and 1980-1995 ............... 5-8

5.7 Components of Historical Change in Total Withdrawals (mgd): 1960-1980....... 5-9

5.8 Components of Historical Change in Total Withdrawals (mgd): 1980-1995....... 5-9

5.9 Comparison of Sectoral Withdrawal Changes Estimated by USGS Inventories
and Linear Regression Models (bgd): 1960-1980 and 1980-1995......... 5-10

5.10 Descriptive Statistics for Public Supply Withdrawals (mgd): 1950-1995.......... 5-11

5.11(a) Linear and Log-linear Regressions of Public Supply Withdrawals on
Total State Population: 1950-1995........................................................ 5-14

5.11(b) Bivariate Relationships between Total Public Supply Withdrawals and
Total State Population: 1950-1995........................................................ 5-15

5.12 Conditional Mean and Median Per Capita Rates of Public Supply
Withdrawals Derived from Bivariate Regression Models: 1950-1995..... 5-16

5.13 Linear and Log-Linear Regressions of Public Supply Withdrawals on
Population Served: 1950-1995.............................................................. 5-17

5.14 Bivariate Relationships between Total Public Supply Withdrawals and
Total Population Served: 1950-1995..................................................... 5-18

5.15 Conditional Per Capita Rates of Public Supply Withdrawals Derived from
Bivariate Regression Models with Population Served: 1950-1995.......... 5-18

5.16 Historical Change in Withdrawals and Per Capita Rates.................................. 5-19

5.17 Components of the 1950-1995 Change in Withdrawals.................................. 5-19

5.18 Stepwise Linear Regression of Total Public Supply Withdrawals: 1950-1995 . 5-21

5.19 Stepwise Log-Linear Regression of Public Supply Withdrawals: 1950-1995... 5-23

5.20 Comparison of Estimated Coefficients of Log-Linear Regression for
Two Time Periods: 1950-1975 vs 1980-1995....................................... 5-24

5.21 Linear Regression of Per Capita Public Supply Withdrawals:

1950-1995........................................................................................... 5-25

5.22 Log-Linear Regression of Per Capita Public Supply Withdrawals:
1950-1995........................................................................................... 5-26

5.23 Predicted vs Actual Values of Per Capita Withdrawals with
Log-Linear Regression.......................................................................... 5-27

5.24 Log-Linear Regression of Per Capita Public Supply Withdrawals Using
Only Continuous Variables: 1950-1995................................................. 5-28

5.25 Predicted Values vs Actual Values of Per Capita Withdrawals with
Log-Linear Regression: 1950-1995....................................................... 5-28

5.26 Descriptive Statistics of Self-Supplied Industrial Withdrawals (mgd):
1950-1995........................................................................................... 5-29

5.27 Correlation between Self-Supplied Industrial Withdrawals and
Potential Driver Variables: 1960-1995................................................... 5-30

5.28 Linear and Log-Linear Regression of Industrial Withdrawals on State
Population: 1960-1995......................................................................... 5-31

5.29 Descriptive Statistics of Per Capita Industrial Withdrawals for Individual
Data Years (gpcd)................................................................................ 5-31

5.30 Linear and Log-Linear Regression of Industrial Withdrawals on
Industrial Employment: 1960-1995........................................................ 5-32

5.31 Descriptive Statistics of Per Employee Withdrawals for Each
Data Year (gped) ................................................................................. 5-32

5.32 Historical Changes in Industrial Withdrawals, Population and Per Capita Use . 5-33

5.33 Component Effects of Historical Changes in Population and Withdrawals........ 5-33

5.34 Historical Changes in Withdrawals, Employment and Per Employee Use......... 5-34

5.35 Component Effects of Historical Changes in Employment and Withdrawals...... 5-34

5.36 Linear Regression of Total Self-Supplied Industrial Withdrawals
(stepwise variable selection): 1960-1995 .............................................. 5-35

5.37 Log-Linear Regression of Total Self-Supplied Industrial Withdrawals
(stepwise variable selection): 1960-1995 .............................................. 5-36

5.38 Log-Linear Regression of Per Capita Industrial Withdrawals........................... 5-37

5.39 Log-Linear Regression of Per Employee Industrial Withdrawals: 1960-1995 .. 5-38

5.40 Components of Change in Industrial Withdrawals Per Employee
(gallons per employee per day): 1960-1995........................................... 5-39

5.41 Comparison of Reported and Predicted Self-Supplied Industrial Withdrawals
Re-estimated Using only Continuous Variables: 1960-1995................... 5-39

5.42 Descriptive Statistics of Total Irrigation Withdrawals (mgd): 1950-1995.......... 5-40

5.43 Comparison of Irrigation Withdrawals, 1950-1995......................................... 5-41

5.44 Linear and Log-Linear Regressions of Irrigation Withdrawals on
Irrigated Acres: 1950-1995................................................................... 5-41

5.45 Trend in Relationship between Irrigated Acres and Withdrawals: 1950-1995... 5-42

5.46 Historical Changes in Withdrawals (AF/yr), Irrigated Acres and Per
Acre Application................................................................................... 5-43

5.47 Components of the 1950-1980 Change in Withdrawals.................................. 5-43

5.48 Components of the 1980-1995 Change in Withdrawals.................................. 5-44

5.49 Linear Stepwise Regression of Total Irrigation Withdrawals............................. 5-45

5.50 Log-Linear Stepwise Regression of Total Irrigation Withdrawals..................... 5-46

5.51 Linear Regression of Irrigation Depth in Inches Per Year, All States:
1950-1995........................................................................................... 5-46

5.52 Linear Regression Models of Average Irrigation Depth for Eastern and
Western States, 1950-1995.................................................................. 5-47

5.53 Log-Linear Models of Average Irrigation Depth for Eastern and
Western States ..................................................................................... 5-48

5.54 Comparison of Predicted and Reported Average Depth of Irrigation
(inches per year): 1950-1995 ............................................................... 5-49

5.55 Components of Change in Irrigation Depth: Western States: 1965-1995;
Eastern States: 1950-1995.................................................................... 5-50

5.56 Descriptive Statistics of Thermoelectric Withdrawals (mgd):1960-1995........... 5-51

5.57 Linear and Log-Linear Regressions of Thermoelectric Withdrawals on
Thermoelectric Generation (46 states): 1960-1995................................ 5-53

5.58 Bivariate Relationships between Total Thermoelectric Withdrawals (mgd/yr)
and Total State Thermoelectric Generation (mkWh/yr): 1960-1995........ 5-53

5.59 Unit Thermoelectric Withdrawals Derived from Bivariate Regression Models:
1950-1995........................................................................................... 5-54

5.60 Components of the 1960-1995 Changes in Thermoelectric Withdrawals......... 5-54

5.61 Linear Regression of Thermoelectric Withdrawals (stepwise variable selection):
1960–1995........................................................................................... 5-56

5.62 Log-Linear Regression of Thermoelectric Withdrawals (stepwise variable Selection):
1960-1995........................................................................................... 5-57

5.63 <