Use of GIS in academic research urban carbon dioxide

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					Factors influencing water consumption for the City
      Use of GIS in academic research: urban
of Phoenix, Arizona dome in Phoenix, Arizona
      carbon dioxide

Elizabeth A. Wentz
Patricia Gober
Department of Geography, Arizona State University
Decision Center for a Desert City
Decision Support Tools




                         For integrated
                         decision-making
Research Topics

• What are the characteristics that affect
  residential water use for the City of
  Phoenix?
• What is the spatial component of these
  factors?
Water price in the City of
Phoenix ranges from $1.38 to
$2.06 per 748 gallons
                                                   Percent of Total
   S
Ap ing
  ar le
    tm F a
      en m
        ts ily
          (4 R
              un esi




                                    0.00
                                           10.00
                                                    20.00
                                                            30.00
                                                                    40.00
                                                                            50.00
                                                                                    60.00




                  its de
                      or nce
                  W m
            C a r or
              ity eh e)
                   o o
            H f P us
               ea h e
                    v o
            O y I eni
                ffi nd x
                   ce u
                      Bu stry
                         ild
                      Sc ing
                   R ho
                     es o
        M              ta l s
          ob             ur
             ile            an
                  H H t
                     om o
                        e tel
                          Pa
         St C D rk
           at om up
             e               l
                 G m e ex
                    ov rc
                      er ia
                        nm l
                                                                                            City of Phoenix water consumption




                      H en
                        os t
                           pi
                              ta
                                l
Why important?

                                                                                   Certainty with respect
                                                                                   to population growth
          U.S. Rank




                                          16

                                          14

                                          12
                     Rainfall in inches




                                          10

                                           8

                                           6

                                           4

                                           2
Uncertainty with                           0

respect to climate
                                           50

                                                53

                                                     56

                                                          59

                                                               62

                                                                    65

                                                                         68

                                                                              71

                                                                                   74

                                                                                        77

                                                                                             80

                                                                                                  83

                                                                                                       86

                                                                                                            89

                                                                                                                 92

                                                                                                                      95

                                                                                                                           98

                                                                                                                                01

                                                                                                                                     04
                                          19

                                               19

                                                    19

                                                         19

                                                              19

                                                                   19

                                                                        19

                                                                             19

                                                                                  19

                                                                                       19

                                                                                            19

                                                                                                 19

                                                                                                      19

                                                                                                           19

                                                                                                                19

                                                                                                                     19

                                                                                                                          19

                                                                                                                               20

                                                                                                                                    20
               Gallons Per Capita Per Day




              150
                    170
                          190
                                210
                                      230
                                            250
                                                  270
                                                        290
       1980

       1982

       1984

       1986

       1988

       1990

       1992



Year
                                                                        1980-2004




       1994

       1996

       1998
                                                              City of Phoenix Annual GPCD,




       2000

       2002

       2004
Average water
consumption per
census tract for
the City of
Phoenix, 2000
• Initial assumption was that INCOME
  contributed to understanding water
  consumption – more income, more
  freedom to use water

                    Water is fairly
                    inexpensive, so
                    something else is
                    controlling varying
                    water usage
Data
Variable   Min    Max      Mean     StDev
Water      51     595      203      76

% Pool     0      86       25       20

Lot        5300   50,400   10,100   5600

% Mesic    <1     86       19       16

Household 1.5     4.7      3.0      0.6
% Pool           Average Lot Size




         Acquired
         from the
         Maricopa
         County
         Assessor’s
         Office
Mesic landscaping by percent of
census tract




  Derived
  from 1998
  Landsat TM
  data
Average household size in single
family housing units




 Acquired from
 the US
 Census, 2000
Ordinary Least Squares Regression


      y i = β 0 + ∑ k β k xik + ε

Water Consumption = Constant + Pool + Lot + Mesic + Household
Geographically Weighted Regression



yi = β0 (ui , vi ) + ∑k βk (ui , vi )xik + εi

For each census tract:
Water Consumption = Constant + Pool + Lot + Mesic + Household
Ordinary Least Squares (OLS), r2 = 0.57
            Estimate             Standard        T value
                                 Error
y           -44.52               19.57           -2.27
% Pool      2.52                 0.18            13.98
Lot         0.002                0.0007          3.26
% Mesic     0.87                 0.22            3.94
Household   48.6                 5.40            9.00

Geographically Weighted Regression (GWR), Mean r2 = 0.80
            Min                  Median              Max
y           -290.10              -38.86              305.78
% Pool      0.29                 2.60                7.73
Lot         -0.028               0.002               0.023
% Mesic     -3.05                0.43                3.90
Household   -26.06               48.20               174.58
Does spatial matter?


Variable                           p-value
% Pool                             0.000 *

Lot                                0.000 *
% Mesic                            0.000 *
Household                          0.000 *

      * Indicates significance at the .05 confidence level
For each census tract:
Water Consumption = Constant + Pool + Lot + Mesic + Household
For each census tract:
Water Consumption = Constant + Pool + Lot + Mesic + Household
What if incentives were created to reduce mesic
landscaping? What would happen to water demand?




                  69000000.00
                  68000000.00
                  67000000.00
                  66000000.00
                  65000000.00
                  64000000.00
                  63000000.00
                  62000000.00
                  61000000.00
                  60000000.00
                  59000000.00
                                1%   5%   10%   25%   50%   75%   100%
Next steps
• Fine tune model development
• Use model parameters in combination
  with urban growth models to simulate
  future water consumption under various
  scenarios
Acknowledgements
• National Science Foundation for financial support
• Barbara Trapido-Lurie for help with the graphics
• Nancy Selover, Nancy Jones, Jana Hutchins for help
  acquiring the data
• Subu Swaminathan and Stephanie Deitrick for help
  with earlier versions of the model