STATISTICALLY EVALUATING WATER CONSUMPTION STATISTICALLY EVALUATING WATER CONSUMPTION HISTORICALLY AND

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  • STATISTICALLY EVALUATING WATER CONSUMPTION HISTORICALLY AND ACROSS MULTIPLE USERS IN VIRGINIA

    Morgan Faye DiCarlo

    Thesis submitted to the Faculty of Virginia Polytechnic Institute and State University in partial

    fulfillment of the requirements for the degree of

    Master of Science

    In

    Biological Systems Engineering

    Julie E. Shortridge

    Venkataramana R. Sridhar

    Andrew Ellis

    May 9, 2018

    Blacksburg, VA

    Key Words: Water Withdrawals, Trend Assessment, Water Systems Modeling

  • STATISTICALLY EVALUATING WATER CONSUMPTION HISTORICALLY AND ACROSS MULTIPLE USERS IN VIRGINIA

    Morgan Faye DiCarlo

    ABSTRACT

    This study explores key aspects of water usage in Virginia via a broad-scale analysis of multiple

    water users through thirty years of time-series records from the Virginia Water Use Data System.

    A full spectrum of users is considered, including water used for energy, industrial, agricultural and

    municipal applications. The extent of the relationship between the volume of water used and drivers

    like economic and climatic conditions are not well defined in humid environments like Virginia.

    Mann-Kendall testing is applied to identify water use trends through time both statewide and at the

    county level. A panel regression is employed to identify relationships between water use and

    explanatory variables of climatic and economic conditions, both spatially and temporally. Key

    trends include that industrial and energy sector water withdrawals per facility are significantly

    decreasing over time. Water used for agricultural applications was found to increase on warmer

    than average years and decrease on wetter than average years, indicating the panel regression

    methodology successfully demonstrated and quantified intuitive trends. Interestingly, municipal

    and industrial water usage had a statistically significant relationship with the GINI coefficient, or

    more unequal rainfall distribution, indicating intraseasonal variability may play an important role

    in water use trends that is not apparent using seasonal averages alone. Overall, this work contributes

    to the understanding of water use trends at the state level for Virginia, and better characterizes

    long-term trends and short-term variability in water withdrawal.

  • STATISTICALLY EVALUATING WATER CONSUMPTION HISTORICALLY AND ACROSS MULTIPLE USERS IN VIRGINIA

    Morgan Faye DiCarlo

    GENERAL AUDIENCE ABSTRACT

    This work applies statistical methods to better understand water use trends through time

    and across the state of Virginia. The primary data source is a record spanning thirty years of water

    use, reported by more than 2,400 users in all counties of Virginia to the Department of

    Environmental Quality (VDEQ). This analysis includes a full spectrum of water sectors, including

    water used domestically (municipal), water used for manufacturing (industrial), agriculture

    applications and water used in the production of energy. The first objective is to determine if water

    use, normalized by changes in population and the number of users, is increasing or decreasing over

    time for each county in Virginia.

    Once the trends through time are identified, the next objective is to better define the

    underlying factors (explanatory variables) which may drive changes in how much water is used.

    One potential factor includes changes in the economic conditions. For example, the economic

    recession in 2008 caused some decline in industrial production. Did this likewise cause a reduction

    in water used by industrial facilities? Particularly, the analysis considers how the annual average

    temperature, total annual precipitation, rainfall variability and the length of heatwaves that occur

    in a given year might impact the amount of water withdrawn in that year. This work addresses a

    knowledge gap about how water use is impacted by climate change in humid environments like

    Virginia.

    This work aims to establish whether or not there is a significant relationship between time,

    climate, economic change and water use in Virginia. The trends identified in this study will support

    the management of water supplies in Virginia and the development a more informed state water

    resources plan.

  • iv

    ACKNOWLEDGEMENTS

    With many thanks to my advisor, Dr. Julie Shortridge, for the incredible opportunity to

    pursue research at Virginia Tech. Facilitating me through a mid-year switch into her research group

    gave me a chance to pursue something I am really passionate about, for which I will always be

    grateful, and I have learned so much under her guidance. Thanks also to my committee members,

    Dr. Venkat Sridhar and Dr. Andrew Ellis, for their time and inputs toward the successful

    completion of this project. Many thanks to our collaborators with the Virginia Department of

    Environmental Quality, Scott Kudlas and Rob Bergholzer, for providing resources and insight.

    To the entire Water Systems lab group, including Julia Reis, Mitchell Paoletti and Morgan

    (II) McCarthy, thank you for your support and the opportunities to present and practice. Likewise,

    I would not be here without the support of my friends and loved ones, including Kyle Jacobs, Suraj

    Gupta, Lauren Eastes, Ellie Weiner, Mariah Gnegy, Elyce Buell, Eleftheria Agioutanti and Zoe

    Schmitt. Finally, thank you to my parents and sister, for absolutely everything.

  • v

    TABLE OF CONTENTS

    TABLE OF CONTENTS ................................................................................................................. v

    LIST OF FIGURES ....................................................................................................................... vii

    LIST OF TABLES ......................................................................................................................... vii

    1. INTRODUCTION ................................................................................................................ 1

    2. LITERATURE REVIEW ..................................................................................................... 3

    2.1 Water Use Conditions in the United States ....................................................................... 3

    2.2 Water Use By Sector ......................................................................................................... 5

    2.3 State of Virginia’s Water Resources ................................................................................. 6

    2.4 Underlying Drivers of Water Use ..................................................................................... 7

    2.4.1 Population ...................................................................................................................... 7

    2.4.2 Climate........................................................................................................................... 8

    2.4.3 Economics ................................................................................................................... 10

    2.5 Analytical Approaches .................................................................................................... 10

    3. OBJECTIVES ..................................................................................................................... 12

    4. METHODOLOGY ............................................................................................................. 12

    4.1 Data Sources and Processing........................................................................................... 12

    4.1.1 Virginia Water Use Data System (VWUDS) .............................................................. 12

    4.1.2 Bureau of Economic Analysis (BEA) ......................................................................... 14

    4.1.3 PRISM ......................................................................................................................... 14

    4.2 Trend Assessment ........................................................................................................... 16

    4.3 Regression ....................................................................................................................... 17

    5. RESULTS AND DISCUSSION ......................................................................................... 21

    5.1 Time Trends .................................................................................................................... 21

  • vi

    5.1.1 Statewide Trends ......................................................................................................... 21

    5.1.2 County Level Trends ................................................................................................... 23

    5.2 Regression Model Structure and Accuracy ..................................................................... 25

    5.3 Regression ....................................................................................................................... 27

    6. FUTURE WORK AND LIMITATIONS ........................................................................... 32