As drought conditions hammer the state, area reservoirs are shrinking, with Blue Mesa predicted to end the year at 23 feet below its winter target.
Despite the past winter season bringing nearly average snowpack, runoff throughout the Gunnison Basin fell well below average, according to the U.S. Bureau of Reclamation’s spring forecast and runoff review, provided Aug. 20.
Warm weather brought the snowpack off the mountains early and summer monsoons failed to provide much of a meaningful drink, while extraordinarily hot, dry conditions persist.
For the Uncompahgre Valley Water Users Association’s storage accounts in area reservoirs, conditions are mixed.
Taylor Park Reservoir
Taylor Park Reservoir, which is at about 72 percent of full capacity, is OK for the association, manager Steve Anderson said. The UVWUA’s storage account there is full, with only about 20,000 acre feet used.
“That’s not the case with our storage in Ridgway (Reservoir). We’ll use all our storage this year out of Ridgway. We’ll have to replenish that one with the winter,” Anderson said.
Ridgway Dam
The UVWUA has been running its delivery of water to shareholders at 80 percent. “Which, in a year like we’ve had, is good,” Anderson said. “With the limited supply, we’ve managed to meet demand at 80 percent.”
The largest impoundment managed in the Aspinall Unit, Blue Mesa Reservoir, peaked at 604,000 acre feet, which is 25 feet below full.
As of Aug. 20, the reservoir was at 521,000 acre feet and peak flow targets for the Black Canyon and lower Gunnison River at Whitewater were met, although the base flow targets for Whitewater were lowered under drought rule provisions.
Aspinall Unit
Paonia Reservoir had shriveled to 2 percent of full capacity, while Silver Jack was reported at 46 percent of full.
Paonia is basically empty, but that isn’t unusual, given the dry year, BuRec hydrologist Erik Knight said.
Paonia Reservoir
“They chose to use their full supply of reservoir water as best they could, but being a small reservoir, sometimes it only lasts until August. So it’s not surprising, at least to us or them, that it’s gone already,” he said.
The reservoir is expected to stay empty as long as more senior water right priorities keep the call on the North Fork of the Gunnison, Knight said.
Other reservoirs in the Aspinall fared better, with Ridgway showing at 71 percent, Crystal at 88 percent and Morrow Point at 94 percent.
Bureau of Reclamation’s spring forecast and runoff review noted the early melt-off of the snowpack. Although rains at the start of June kept flows into reservoirs in the Aspinall Unit elevated longer than was expected, those levels plunged to “much below normal” by mid-month. Monsoon activity was anemic, providing “almost no precipitation this summer,” the report also said.
Since runoff ended, hot and dry conditions have prevailed, with near-record dry conditions occurring in April and May. Although those actual conditions caused a higher than normal forecast error, actual runoff volume still fell within the lower range of predictions.
The National Weather Service’s August weather outlook did not hold encouraging news. It found a high probability of below-normal precipitation and above-normal temperatures heading into fall…
The U.S. Drought Monitor shows all of Colorado in at least moderate drought, with Montrose and surrounding counties in either severe or extreme drought.
The monitor on Aug. 20 noted temperature-breaking records in cities across the West, as well as massive wildfires that broke out in California. The monitor’s report, too, calls the monsoon season a “bust” for much of the Southwest.
Intake structure during construction in 1961. Photo Credit Reclamation.
Here’s an in-depth look at the sedimentation problem at Paonia Reservoir from Emily Benson writing for The High Country News. Here’s an excerpt:
The root cause of the problem at the reservoir had been building since the dam was finished in 1962. Year by year, sediment quietly collected on the reservoir bottom, gradually raising its floor. Once the sediment was level with the dam outlet, where water is released downstream, any debris that washed into the reservoir threatened to clog the opening and make the dam inoperable. In the fall of 2014, personnel worked 10-hour days for two weeks to clear logs, branches and dirt from the outlet, by hand and with an excavator. Some of the workers stood directly on waterlogged sand, digging out the grates with pitchforks. When the dam was newly built, they would’ve needed a crane 70 feet tall to reach the same spot.
Silt, sand, gravel and clay are accumulating in nearly all reservoirs in the West, leaving less room to capture water for storage or for flood prevention. Behind many dams, space is starting to run out. Ignoring the problem could jeopardize the West’s water supply in the coming years. To avoid that, water managers are dredging behind dams, retrofitting outlet works and looking for ways to safely pass sediment downstream. “It’s not an immediate crisis,” Randle says. “But it is sort of a ticking time bomb.”
