A MULTI-SCALE ANALYSIS OF SINGLE-FAMILY RESIDENTIAL WATER USE IN THE PHOENIX METROPOLITAN AREA1

Studies that evaluate determinants of residential water demand typically use data from a single spatial scale. Although household-scale data are preferred, especially when econometric models are used, researchers may be limited to aggregate data. There is little, if any, empirical analysis to assess whether spatial scale may lead to ecological fallacy problems in residential water use research. Using linear mixed-effects models, we compare the results for the relationship of single-family water use with its determinants using data from the household and census tract scales in the city of Phoenix. Model results between the household and census tract scale are similar suggesting the ecological fallacy may not be significant. Common significant determinants on these two spatial scales include household size, household income, house age, pool size, irrigable lot size, precipitation, and temperature. We also use city/town scale data from the Phoenix metropolitan area to parameterize the linear mixed-effects model. The difference in the parameter estimates of those common variables compared to the first two scales indicates there is spatial heterogeneity in the relationship between single-family water use and its determinants among cities and towns. The negative relationship between single-family house density and residential water use suggests that residential water consumption could be reduced through coordination of land use planning and water demand management.