MunicipalDroughtRestrictionsInColorado

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KENNEY, KLEIN, AND CLARK TABLE 2. Restrictions on Outdoor Water Use (May through August, 2002). Municipal Water Provider Dates of Voluntary Limits Lawn Watering Restrictions Dates of Specified Mandatory Watering Limits Times Specified Watering Length Other Restrictions Start Date Residential of Drought Car Planting Surcharges Washing New Sod Providers Limiting Lawn Watering to Once Every Three Days (2 -1/3 timestweek) Thornton May 8 to August 31 None Voluntary Voluntary Restriction Restriction Aurora None May 15 to August 31 6 pm to 9 am July 6 Denver Water May 8 to June 30 July 1 to August 31 6 pm to 9 am 3 hours per Restricted Voluntary day Restriction Westminster May 22 to July 31 August 1 to 31 6 pm to 9 am 3 hours per Restricted Restricted day Cities Limiting Lawn Watering to Twice a Week Fort Collins June 26 to July 21 July 22 to August 31 6 pm to 10 am3 Voluntary Restriction Boulder May 8 to May 20 May 21 to August 31 6 pm to 9 am 15 min. per Restricted zone Louisville None May 15 to August 31 7 pm to 7 am 10 min. per zone Cities Limiting Lawn Watering to Once a Week Lafayette None May 22 to August 31 5 -7 am or 8 -10 pm 2 hours per May 21 Banned Banned day Entirely Entirely 1 Programs described are only for the study period May 1 to August 31, 2002. Several cities have further modified their water restriction pro- grams since the end of this period. Nalues are for the period of most stringent restrictions. 3Unless using automatic (i.e., programmable) sprinkler systems, then midnight to 4 am. 4 May 21, the date on which the City Manager adopted mandatory watering restrictions through emergency rule, is used as the starting date of Boulder's mandatory restriction period, although the Boulder City Council did not formally approve the restrictions until June 4 and enforcement did not begin until June 10. Data and Methods For each of the eight study regions, daily water use data from May 1 to August 31, 2002, were collected directly from the relevant municipal water agencies. For purposes of comparison, the same data were also collected for the two preceding years. Given the high rates of growth for some cities during this period, pop - ulation data from the Colorado State Demographer's office, from the water utilities for 1999 to 2001, and from 2002 population estimates derived from those , data were used to convert overall water delivery fig- ures to per capita water consumption (see Table 1) — something the cities often do not do in their own cal- culations of water restriction effectiveness. Account- ing for population growth is necessary to provide an accurate reflection of how well individuals conserved water; failure to account for population growth under- states the effectiveness of restrictions. This informa- tion, combined with knowledge of when restrictions were initiated (shown in Table 2) is all that is neces- sary to provide rudimentary estimates of water restriction effectiveness. Calculating "expected use" requires the use of sta- tistical models that can explain the variability in observed daily per capita water use (the dependent variable) with respect to climatic factors, namely the drier conditions and warmer temperatures associated with drought. For each city, daily data on maximum temperature and precipitation were used as predic- tors in a multiple linear regression equation to predict what water use would have been each day in the absence of watering restrictions. A one -day lag vari- able also was included in the regression equations to JAWRA . 80 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION