1. Use and Effectiveness of Municipal Water Restrictions During Drought in Colorado Bobbie Klein and Doug Kenney 2002 Drought – the Context Study Methodology Results The winter and spring of 2002 were abnormally dry in Colorado. In the South Platte Basin snowpack was never more than 55% of average. Snowmelt provides a substantial portion of the municipal water supply in Colorado’s Front Range. Reservoir storage, which is vital to the Front Range water supply, quickly fell to very low levels. Some reservoirs were virtually empty by the end of the summer. By early May, the entire state was a moderate to extreme drought, though the South Platte basin had avoided the worst of it. This would quickly change as the weeks wore on. We selected eight large and small municipal water providers in the area around Denver extending north to Ft. Collins. Their estimated 2002 populations are shown in this table. Our study focused on outdoor water restrictions since outdoor use accounts for over half of all residential use in Colorado. We collected daily water use data from each provider, as well as daily precipitation and maximum temperature data, for the period May 1 – August 31. We compared water use in 2002 to use during the same period in 2000 and 2001 for both voluntary and mandatory restriction periods and for the entire study period. The Western Water Assessment launched this study to answer these questions: How did Colorado Front Range cities respond to the 2002 drought? Were these responses effective? If so, by how much? We measured water use three ways: *Overall deliveries in 2002 versus 2000/01 *Per capita use in 2002 versus 2000/01 *Expected per capita use in 2002 versus actual per capita use in 2002. Expected per capita use is our estimate of what per capita use would have been in 2002 absent restrictions--based on the assumption that demands that year would be higher than in normal years due to the hot, dry conditions. To estimate expected per capita consumption maximum daily temperature and precipitation were used as predictors in a multiple regression equation. This table summarizes the various watering restrictions and the period in which they were effective. The most typical was the “circle- square-diamond” schedule that permitted watering every third day. The next most common was the twice weekly schedule. One city was forced to limit outdoor watering to once a week. Some cities also limited the time of day and the number of hours each day that watering was permitted. Additional restrictions are noted. This table summarizes the percent savings in water use. In general, savings during mandatory restrictions were greater than during voluntary restrictions, and cities allowing watering only one or two days per week saved more than cities allowing watering every third day. In this table we show water savings in terms of acre feet. One acre foot equals 325,851 gallons and is roughly the amount needed to satisfy the needs of a Colorado family of 4 for one year. Union Reservoir in Longmont holds approximately 12,000 acre feet. Western Water Assessment Natural Resources Law Center