Colorado Front Range residents are using less water, but some parts of the Western Slope have seen per capita water use explode in the past decade, according to a new state study.

The number of gallons per person used daily in Denver and other South Platte River basin cities decreased 13.6 percent between 2000 and 2008, to 178 gallons from 206 gallons.

Water use in Colorado Springs and Arkansas River basin communities decreased during that time by 11.2 percent to 190 gallons, down from 214.

The catch: Population growth still is pushing total water use up — and state officials project shortages.

Residents of western Colorado on average consume more gallons per person each day.

Water use rose to 256 gallons per person in the Colorado River basin, 332 in the Rio Grande, and 236 in the Dolores/San Juan, according to Colorado Water Conservation Board data.

Denver and suburban water suppliers plan to divert more water from mountain rivers on the west side of the Continental Divide, pumping it through tunnels to new and expanded Front Range reservoirs to sustain residential and industrial development.

A federal study based on 2000 census data ranked Colorado’s average consumption of 240 gallons per person fifth among states, behind Nevada (336) and Utah (293). The national average was 179 gallons.

The new Colorado Water Conservation Board data indicate wide variations in consumption statewide.

Residents of Pitkin County, home of Aspen, used 1,851 gallons per person each day, the data show, as Elbert County folks used 111 gallons each.

Water analysts attributed the decreasing water use in Front Range cities to conservation programs that create financial incentives.

Denver Water, for example, pays customers up to $150 to replace a toilet, shower or washing machine with a newer, more efficient model.

“Front Range utilities have done a great job at reducing per capita water use. Everyone’s individual water use has dramatically decreased,” said Drew Beckwith, water policy analyst for Western Resource Advocates, a Boulder-based environmental policy and law group.

Still, fewer than 20 percent of Denver Water customers have received rebates. State planners project population growth will leave Colorado facing severe shortages by mid-century.

Bruce Finley: 303-954-1700 or bfinley@denverpost.com