An analysis of five weeks of Aspen water-treatment plant data show that local water users cut consumption by an average of 20% in the four weeks after Stage 2 water restrictions took effect, compared with the week before the stricter regulations were in place.
However, year-over-year data shows that water use in 2020, over the course of the past five weeks, was down by smaller amounts compared with the non-drought year of 2019.
Stage 2 water restrictions began Sept. 1, with the goal of reducing water use by 15% to 20% compared with “current use,” according to a news release announcing the restrictions.
That appears to have been achieved, as average daily water use was 5.86 million gallons from Aug. 24 to Aug. 30, according to water-treatment plant data provided by city of Aspen staff and analyzed by Aspen Journalism. Average use dropped to 5.08 million gallons per day the following week and to 4.7 million gallons per day over the four weeks from Aug. 31 through Sept. 27.
Comparing average daily water use with a non-drought year provides further context when examining the degree to which restrictions have influenced water use in recent weeks. Aspen Journalism’s analysis of the city’s daily treated volumes included totaling water use on a per-week basis and finding the average consumption per day for a given week. Those numbers were compared to average daily totals from corresponding seven-day periods in 2019, a non-drought year in which water restrictions were not in place for the utility’s approximately 4,000 customers in the city of Aspen and surrounding neighborhoods.
That analysis showed an average decline of 10% when comparing five weeks in 2019 versus 2020. However, the differences between weekly totals from year to year varied considerably. In addition, a large decline in weekly water use in 2020 compared with 2019 often corresponded with a burst of rain or snowfall, levels that were sourced from National Oceanic and Atmospheric Administration data. For instance, over the week of Sept. 7 to 13, weekly water use declined by 36% from 2019 to 2020. This steep decline is probably related to the three-day snowstorm that occurred that week in 2020, which dropped on the city a cumulative 8.5 inches of snow Sept. 8 to 10, according to NOAA data.
In contrast, the week of Sept. 21 in both 2019 and 2020 saw neither rain nor snow, according to NOAA data. That week in 2020, the city used 6.2% less water than in the same week in 2019, according to Aspen Journalism’s analysis. Precipitation levels were similar for the five weeks spanning late summer and early fall, with 2020 having two more days and 0.7 more inches of rain compared with 2019, according to NOAA data.
Declines in water use may relate to rainfall and snowfall since weather events prompt the city’s parks and open space department and residents to stop or reduce watering to parks, gardens and open space, said Steve Barr, the city of Aspen’s parks operations manager. Because approximately 60% of total municipal water is diverted to parks, landscapes and gardens, rain and snowfall prompt reduced water use and probably correspond to declined treatment-plant figures.
“A period of rain (in late August) allowed us to shut down irrigation for three or four days. Truly, this saves the largest amount of water,” Barr said. Yet, more data would need to be analyzed in order to draw statistically sound conclusions about the relationship between weather and water use for the entire city water system, said Steve Hunter, utilities operations manager for the water department.
Due to the many factors that influence treatment-plant numbers, it is difficult to discern from the data how resident behavior changed after the Sept. 1 water restrictions and how behavioral changes influence city water use, Hunter said.
City population, visitation, humidity, weather and special events also influence the daily volume of treated water, according to Hunter.
“Just like our weather, no two days are exactly the same,” he said.
The reduction targets identified with Stage 2 restrictions are meant to give water users a goal to hit compared to their normal usage, according to water plant officials.
Community adaptation efforts
Aspen City Council enacted Stage 2 water restrictions after the U.S. Drought Monitor on Aug. 18 classified all of Pitkin County to be in extreme drought. The goal of the restrictions is to protect the streamflow of Castle Creek, which provides the majority of Aspen’s water, with flows throughout the Roaring Fork River basin running 40% to 70% below median, according to a memo from the utilities department concerning the water restrictions.
In 1997, the city agreed with the Colorado Water Conservation Board to maintain 12 cubic feet per second on Castle Creek, except in extreme drought conditions, according to the state resolution. Dropping below this rate threatens the aquatic ecosystem, as warmer waters stress native fish populations and alter the aquatic environment through increased algal blooms, according to Brad Udall, a water and climate research scientist at Colorado State University.
Many local businesses report following Stage 2 guidelines, which may be associated with the 20% decline in water in the four weeks after the week of Aug. 24. The restrictions put residents and businesses on a staggered watering schedule and prohibit the construction of new landscapes and water systems, as well as prompt other regulations. (Residents and businesses, for example, cannot wash sidewalks with treated city water.) Managers and directors at Aspen Alps, The Gant, Limelight Hotel, Aspen Mountain Lodge and Aspen Meadows Resort said they follow the new protocol.
“Everyone cares about water use and is very compliant with water restrictions,” said Aspen Mountain Lodge general manager Allison Campbell. “We see it when we’re touring around our state, how dry we are.”
Many businesses are implementing additional measures to reduce water. Staffers at Aspen Mountain Lodge winnowed their watering window to 15 minutes every three days, compared with every other day required by Stage 2, according to Campbell. At Bumps restaurant, which sits at the base of Buttermilk Mountain, staffers are testing new technology that reduces the quantity of water needed to thaw food, according to Ryland French, energy manager at Aspen Skiing Co. Businesses could not provide data for these reductions, as many do not collect daily water data but make changes based on the monthly water bill from the Aspen utilities department, according to Campbell, French and Aspen Meadows Resort general manager Jud Hawk.
Other major water users, such as the city golf club and the parks and open space department, have enacted new water practices following the Stage 2 announcement. Golf club staffers cut irrigation to native plants on the course and reduced water to the driving range by 75%, from 62,667 gallons dispensed on the driving range each night to 15,667, according to golf director Steve Aitken.
After Sept. 1, the parks department shortened watering times and limited those periods to every other day. Staffers continued low water-use practices established during the 2018 drought, such as limiting water to native-plant zones, Barr said. From this past August to September, the department reduced irrigation to parks and gardens by an average of 43%, according to data provided by the parks and open space department. The department used less water in 83% of Aspen parks and gardens in September compared with August, according to parks department data.
More changes needed to maintain streamflows
This summer is not the first time that the city of Aspen has tried to meet water-use reduction targets. In 2013, the water department enacted water restrictions with a 20% reduction goal. The city did not meet this target, according to a 2016 water-availability study by the Wilson Water Group. In 2015, the water department lowered the Stage 2 reduction goal to 15%, according to the 2016 study.
The water department also enacted Stage 2 restrictions on Aug. 13, 2018. No analysis was conducted on whether the city met the 15% reduction target, according to Tyler Christoff, director of utilities for the water department.
Despite current drought conditions, Castle Creek’s streamflow remains above the state-mandated minimum level. The creek averaged 35.6 cfs in the five weeks from Aug. 24 to Sept. 27, with a minimum cfs of 32 the week of Sept. 21, according to water department data.
The days of Aug. 24 to Sept. 27 fall within the city’s peak water-use period, which runs from June to September, according to the 2016 water availability study. Higher temperatures and evaporation rates mean that Aspen’s parks and landscapes demand more irrigation, Barr said. Last week, the parks department began blowing out and shutting off its irrigation system for the winter, according to Barr. This may cause a decline in demand for city water.
While current drought conditions did not endanger running below the minimum instream flow, studies show that climate change will demand revisions to city water sourcing and use in order to keep Castle Creek above 12 cfs.
Temperature is predicted to rise throughout Colorado by 2.5 to 6 degrees Fahrenheit by 2065, according to a report by the research institute Western Water Assessment. Rising temperatures increase evaporation in all forms, transferring water from streams to the atmosphere, Udall said.
“Under a warming climate, the atmosphere has a greater thirst for water. It wants to hold more water as it warms,” he said.
Rising temperatures and the resulting increased evaporation can be expected to reduce Castle Creek’s streamflow by 35% by 2065, according to a 2017 study done by Headwaters Corporation for the city of Aspen. This reduced streamflow, in conjunction with population growth, will lower Castle Creek’s streamflow below 12 cfs, according to a 2016 water availability study by Wilson Water Group. Yet, 12 cfs can be maintained if the water department draws more municipal water from local wells and implements a water-reuse program, where the city golf course is irrigated by upcycled wastewater treatment plant water instead of water from Castle Creek, according to the 2016 study. While the 2016 study concludes that Castle Creek’s minimum streamflow can be maintained with these mitigatory actions, Aspen officials in 2018 asked the state for rights to 8,500 acre-feet of water storage to prepare for the effects of climate change.
“In extreme or prolonged drought, reservoir storage would help create a more resilient water supply for the Aspen community,” Hunter said.
The Wilson study’s authors also suggest implementing Stage 2 or Stage 3 water restrictions to maintain Castle Creek’s instream flow. Stage 3 water restrictions aim to reduce water use by 20%. But the authors add that if city water users fall short of the target reductions, well water can fill the deficit to ensure the required 12 cfs.
Stage 2 conditions will last as long as Pitkin County remains in extreme drought, which will probably be into 2021, Hunter said. In April, the water department will assess winter snowpack — which is predictive of spring and summer streamflow — and will decide to continue State 2 or lift it, Hunter said.
Hunter believes the ordinance unites the city in environmental goals.
“We believe the community’s knowledge and participation in conservation practices creates a more resilient future,” he said.
This story ran in The Aspen Times on Oct. 10.