Drinking water quality isn’t the only thing officials are worried about in the anticipated event of debris flows in the Colorado River and tributaries because of local fires.
Fisheries and irrigation systems are among other resources that could be negatively affected. And in an effort to try to minimize potential impacts to everything from agriculture to municipal water supplies to endangered fish, discussions are scheduled involving reservoir operators and other entities that play a role in Colorado River management to consider how releases of stored water might be arranged and coordinated as a response to debris flows.
The goal would be to boost river flows in order to reduce the debris and ash concentrations related to flows coming off burn areas.
“Is there anything we can do in an emergency mode to increase the dilution capacity of the Colorado River? We don’t have a lot of other tools in the toolbox as far as we can tell” to deal with the debris flow threat, said Tom Chart, director of the Upper Colorado Endangered Fish Recovery Program.
That program is focused on recovering the humpback chub, bonytail, razorback sucker and Colorado pikeminnow — all endangered species — in the upper Colorado River and Green River.
Part of the recovery effort focuses on enhancing, when needed, river flows in a critical 15-mile stretch of the Colorado River between where Grand Valley irrigation water is diverted in the Palisade area and where the river joins the Gunnison River downstream.
Already this summer, reservoir operators, utilities, water policy officials and others have been participating in weekly phone calls to discuss how flows in that river stretch can be boosted where possible. Because of the ongoing drought, flows there have been falling well below the target minimum of 810 cubic feet per second intended to help protect the river habitat for both endangered fish and the prey on which they feed.
Chart said there has been a lot of great cooperation going on this summer to boost flows for the fish, but it nevertheless has been a tough summer for the species. Now the specter of debris flows from fire poses yet another threat that could prove a breaking point for some fish.
Chart said native fish are pretty tolerant of a wide range of water quality conditions, having evolved to live with periods of high seasonal river turbidity.
Still, ash going into the river can shock the ecosystem by boosting alkalinity in the water, he said. Another concern is fire retardant being washed into the river. Chart said some retardants can have toxic substances in them, and while fire crews try to keep retardant away from drainages, a big storm can still wash retardant into rivers.
He said runoff from burn areas has resulted in deaths of endangered fish locally before, including in one incident involving humpback chub in Westwater Canyon on the Colorado River decades ago.
“It did not decimate the population, but it definitely reduced the numbers,” Chart said.
Fish likewise have died in similar fashion in Desolation Canyon on the Green River.
With Colorado River levels so low already below Palisade, flooding from a burned area would result in even higher concentrations of ash and debris in the river than otherwise would be the case. The purpose of the upcoming discussions, scheduled to kick off with a conference call Thursday, are to consider how releases by reservoir operators might be carried out to enhance river levels when a debris flow appears imminent based on weather forecasts, or has occurred.
The upcoming conference call is being coordinated by the U.S. Bureau of Reclamation and Colorado River District, both reservoir operators in the Colorado River watershed in Colorado. The river district also is a water policy entity on the Western Slope.
Irrigators could be another beneficiary of well-timed boosts in flows to respond to fire-related flows. Max Schmidt, manager of the Orchard Mesa Irrigation District, said he’s not worried about a debris flow affecting the delivery systems.
But it could be detrimental to orchards and vineyards that may have finer screens and filters than what are on the irrigation district’s system, he said.
“Anything that filters water before being pressurized, it could make a big difference,” he said.
Sprinklers and drip-irrigation systems could be affected, he added.
Schmidt said ash and debris also could impact sensors the district uses for water quality sampling.
He said his concern with this year’s fires is the widespread burning that occurred. He has seen ash reach the river as a result of wildfire in the Glenwood Springs area before and didn’t hear of water users having problems.
“But I think this might be a larger quantity (of ash) with all these fires,” he said.
The Pine Gulch Fire north of Grand Junction is now the largest in the state’s history. Chart said the Pine Gulch Fire could have some impacts to Roan Creek and to the Colorado River itself, but he sees the Grizzly Creek Fire in Glenwood Canyon as a bigger threat to the river because it happened on steep slopes so close to the river.
“We’re most worried about the immediate effects right there at Glenwood (Springs),” he said.
There, the concern isn’t endangered fish but other native species, as well as sport fish, in a community where fishing is part of the local tourist economy.
The city also faces a threat to its municipal water supply, which is sourced in drainages that burned in Glenwood Canyon, but is delivered via infrastructure rather than the river.
From the perspective of the endangered fish program, the first critical habitat on the river that could be affected starts in the Rifle area, Chart said.
Chart is happy about efforts the U.S. Geological Survey has announced to beef up water quality monitoring so agencies can be alerted quickly in the case of debris flows reaching the river.
“It was great to hear that (USGS) is trying to get out in front of this, too,” he said.