Snowpack estimated to be 190% of the average in the Dolores River Basin will create a significant whitewater boating season below McPhee Dam, and help to improve the ecology of the often dry Lower Dolores River.
Details were hashed out by the Native Fish Monitoring and Recommendation Team meeting Monday at the Dolores Water Conservancy District Office.
DWCD and Bureau of Reclamation officials estimate a 30- to 60-day recreational water release from the dam, which is timed for whitewater boating, native fish needs and geomorphology of the river.
The release is expected to begin in middle to late May, but the date has not been determined.
It will be announced at a boaters meeting tentatively set for early May at the Dolores Community Center.
“A lot of boaters are zeroing in on the Dolores River this year,” said Amber Clark, executive director of the Dolores River Boating Advocates. “My phone has been ringing off the hook.”
The last time a whitewater boating release occurred was in 2019, which took place for 38 days after a 140% snowpack winter.
The lake is nearly empty of active supply, so it needs 200,000 acre-feet of water to provide farmers with their full allocation, which they have not had for three years.
According to the Colorado River Basin Forecast Center, as of April 1, there is a 90% probability that the current snowpack would create 440,000 acre-feet worth of runoff.
The timing and exact volume of the spring runoff are difficult to determine exactly.
To account for variables in runoff and snowpack, DWCD errs on the conservative side and estimates at least 130,000 acre-feet of water will be available this year to release downstream for boaters, which equals 30 to 40 days at various levels ranging from boatable flows from 400 cubic feet per second to 4,000 cfs or higher.
Unpredictable factors, such as a delayed spring, snowpack estimates, spring precipitation, temperature, cloud cover, wind, evaporation, soil moisture and dust on snow all factor into efforts to try and predict the amount of water that will be available for the dam release.
Five snow telemetry sites and overflight lidar technology that estimate snowpack volume in the 800-square-mile basin are good tools but also have limitations considering the vast, variable terrain and climate factors, said Eric Sprague, DWCD water resource specialist.
Models for soil moisture show a deficit, “so we expect some losses,” as runoff is absorbed, he said.
Add into the formula that McPhee Reservoir is not a “fill and spill” operation.
Farmers receive the water before the lake fills; therefore, reservoir managers are conservative to ensure a full supply is available for them as they calculate the timing and amount for the boating and ecological release from the dam.
Supporting rafting and downstream river ecology is a component of the management plan for the Bureau of Reclamation reservoir, said Robert Stump, of the BOR office in Cortez.
The MMR Team has been meeting for 20 years to help manage downstream releases on the Dolores River. The collaborative group includes boaters, reservoir managers, scientists, environmentalists, farmers, Colorado Parks and Wildlife, public land officials and politicians.
They are all planning for the best use of the water earmarked for the river below the dam.
Flushing flows are critical for a healthy river system, explained ecologists and aquatic biologists.
John Harvey, a geomorphologist and associate professor at Fort Lewis College, said flushing flows will help clear away sticky mud that has built up on the rocky river bottom from years of drought and minimal flows.
Clearing the mud cleans the river cobble relied by the three main native fish of the Lower Dolores – the bluehead sucker, roundtail chub and flannelmouth sucker.
The native fish are not endangered or threatened, but they struggle with the chronic low water conditions below the dam.
Supporting their habitat needs as much as possible when there is excess water is important, said DWCD General Manager Ken Curtis, because it helps to prevents them from becoming listed under the Endangered Species Act and associated federal regulations.
Dan Cammack, CPW native aquatic species biologist for the Southwest region, reported a recent confirmed sighting of a razorback sucker and Colorado pike minnow in the Lower Dolores River within Colorado near the Utah border, upstream of the confluence with the Colorado River. The two fish species are listed under the Endangered Species Act and mostly inhabit the Colorado River.
Jim White, CPW aquatic biologist of Durango, said high flows from the McPhee dam release are needed to send water into side canyons of the Lower Dolores River, which support critical habitat for younger native fish that find refuge there.
River specialists added the flushing helps to reduce channel “armoring” that prevents the river from reaching its natural flood plain needed for ecological benefits.
For example, mimicking a natural spring flood will push waters out of the channel and onto a wider flood plain that carry cottonwood seeds, said Cole Crocker-Bedford, a Slick Rock landowner with experience in fish habitat restoration.
When the flows recede back to the channel, the seeds grab hold in the moist soil of the wider flood plain and put down roots, he said.
The level of the flushing flows was debated. Some said 2,500 cfs over a period of seven days is sufficient to meet objectives, while another urged 4,500 cfs for a week or more to undo armoring and water the flood plain.
The team agreed that “suppressing the spawn” tactics should be considered in this years’ dam release.
The idea is to use increased flows in April or May to drop the water temperature below the level that triggers native fish to spawn. This allows the spawn to be delayed until after the rafting flows subside, giving the fish a better chance for survival.
Crocker-Bedford said another issue with the Lower Dolores River habitat is the lack of natural woody debris that attracts bugs relied on by fish for food. McPhee dam traps the wood, which should be collected and relocated downstream to help the fishery, he said.
Timing to secure a full reservoir can cause glitches in the boating release. For example, in 2019, the district reserved water for a high flow release to accommodate Memorial Day weekend.
As the rafting season played out, the district cut the high flows to 400 cfs out of concern releasing too much could jeopardize a full irrigation supply, then ramped them back up when it became clear the full reservoir threshold would be met.
The situation was a problem for the boaters that planned trips for the higher flows, said boating representative Sam Carter.
Reservoir officials say they work to accommodate boaters and sometimes adjustments in the flow regime are needed due to the unpredictability of weather and the late runoff.
At any rate, boaters don’t have to wait for the controlled dam release to run the Lower Dolores River.
Natural flows from snowmelt and tributaries, especially Disappointment Creek, have already opened up boating flows on the Dolores River in the premiere multiday run through Slick Rock Canyon.
As of April 12 at 10 a.m., the Dolores River at Slick Rock and Bedrock was running 2,400 cfs, according to the DRBA river flow website.