Climate change could threaten Carbondale water supply
A new climate study and a first-ever call on a tributary of the Crystal River offer a glimpse of the future for Carbondale’s water supply.
A Vulnerability, Consequences and Adaptation Planning Scenario report by the Western Water Assessment found a strong upward trend in local temperatures over the past 40 years, which could threaten local water supplies.
“This report sort of drove the message home that (climate change) is here, and it’s no longer a conceptual discussion — it’s a pragmatic discussion,” Carbondale Mayor Dan Richardson said. “It was sobering from that perspective.”
According to the report, the average temperature since 2000 has been 2.2 degrees warmer than the 20th-century average. Water year 2018 was more than 4 degrees higher than the 20th-century average and was the warmest recorded in the past 120 years.
Warmer temperatures are bad news for the watershed because they have an overall drying effect, even if precipitation remains constant. According to the report, Roaring Fork River streamflows since 2000 have been about 13% lower than the 20th-century average, due, in part, to warmer temperatures. By 2050, a typical year in the Roaring Fork Valley is projected to be warmer than the hottest years of the 20th century, which means mild drought conditions even during years with average precipitation.
“Just the warming temperatures alone are enough to tell us drought will be a concern in the future and drought conditions are likely to persist for longer,” said WWA managing director Benét Duncan. “What does that mean for the water supply?”
Drought illustrates vulnerability
The summer of 2018’s historic drought illustrated a vulnerability in Carbondale’s water supply that surprised local officials. Senior water-rights holder Ella Ditch, which serves agriculture lands south of Carbondale, placed a call for the first time Aug. 8.
This meant that because there wasn’t enough water in the Crystal for Ella Ditch to divert the amount to which it was legally entitled, junior water-rights holders, including Carbondale, had to reduce their water use — threatening the domestic water supply to roughly 40 homes on the Nettle Creek pipeline.
“We had a situation last summer where we were inches away from having to shut down our water-treatment plant at Nettle Creek because there was a more senior call on the river,” Richardson said. “When you look at the water rights we have on paper, most municipalities feel confident their water portfolio is resilient and can stand the test of time, but that was paper water. And when it comes to wet water, we were pretty vulnerable.”
Carbondale applied for and received an emergency substitute water-supply plan from the state engineer. The emergency plan allowed for a temporary change in water right — from agricultural use to municipal use — so that another irrigation ditch could provide water to the town.
The East Mesa Ditch Co., whose water right is senior to Ella Ditch’s, agreed to loan the town 1 cubic foot per second of water from Sept. 7 to Dec. 7 under the agreement. However, Carbondale had to borrow the water only until Sept. 28, when the call was lifted on Ella Ditch. East Mesa Ditch is located upstream from Ella Ditch. Both are used to irrigate lands farther downstream on the east side of the Crystal River.
The town didn’t pay East Mesa Ditch for the water but paid the company about $5,000 in legal and engineering fees to draw up the water loan agreement, according to Town Manager Jay Harrington.
A wake-up call
Although Carbondale has other sources it can turn to for municipal use, including wells on the Roaring Fork, the summer of 2018 and the VCAPS report were a wake-up call.
“Nettle Creek is a pretty senior right, and we didn’t anticipate it to be called like it was,” Harrington said.
Potential solutions to another Ella Creek call outlined in the report include moving away from Crystal water sources to Roaring Fork sources and providing upstream pumps to the homes on the Nettle Creek pipeline.
“I think (the report) gives one of the clearest pictures of where we are heading and what we need to look at as a municipality as the climate changes,” Harrington said.
Aspen Journalism covers rivers and water with The Aspen Times and other papers with Swift Communications. More at aspenjournalism.org.
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