Delta facing flooding concerns with reservoir releases
After filling completely last summer for the first time since 2002, Blue Mesa reservoir is currently sitting at half-full, as water officials prepare for large amounts of spring runoff. At the same time, citizens of Delta have voiced concerns about flooding, as they await peak flows from the North Fork of the Gunnison River to combine with releases from Blue Mesa.
The Upper Gunnison River Water Conservancy District (UGRWCD) discussed the reservoir situation during a regular meeting on Monday, April 28. UGRWCD manager Frank Kugel said Blue Mesa was dropping at a fast rate. At press time, the reservoir was 49 percent full, according to information provided by the United States Bureau of Reclamation.
UGRWCD attorney John McClow said strong flows were expected through the Black Canyon of the Gunnison throughout the spring, as Bureau of Reclamation water managers amp up water releases from Blue Mesa Reservoir, and other reservoirs in the Wayne Aspinall unit, to match an increasing amount of spring runoff.
Aspinall also includes the Morrow Point and Crystal reservoirs. All three of the reservoirs were authorized in 1956 by the Colorado River Storage Project Act. The dams for each reservoir also generate hydroelectric power that is sold by the Western Area Power Administration, a division of the Department of Energy.
The Bureau of Reclamation is responsible for maintaining water for the generation of electricity, a process that requires constant planning to ensure adequate flows, but the Bureau must also make room for expected runoff.
Over the course of the winter, Bureau of Reclamation hydrologists monitor snow packs and compare current readings to historical data in an effort to forecast spring runoff. The bureau uses two main indicators—the depth of the snow pack and the snow’s water content, also known as snow water equivalent.
The bureau’s April 1 forecast calls for over 1 million acre feet of water to flow into Blue Mesa during the spring and early summer, more than twice the predicted amount of last year. Blue Mesa can store approximately 940,000 acre feet of water. One acre foot is approximately 325,900 standard U.S. gallons, enough water to cover an entire football field to a depth of six inches.
McClow said earlier in the day the bureau increased the release rate for the Crystal Reservoir, the final dam in the Aspinall series. “They’re running at the capacity of the tubes and power plants,” McClow said of the hydroelectric dam. “They are planning to spill Crystal, at least twice,” he said, referring to a situation where water reaches the spillway of the dam and is released “uncontrolled.”
But the large releases into the Black Canyon of the Gunnison are causing flooding concerns in Delta, where the North Fork River and Gunnison River meet. McClow said public officials in Delta were concerned that the flows coming out of Blue Mesa might combine with above-average flows on the North Fork during peak runoff, which can occur between May and June, depending on the temperature.
UGRWCD board member Ralph Grover, who drove through Delta earlier in the afternoon, said, “The water under the bridge at Delta is really high… I can see their concerns.”
McClow said the U.S. Fish and Wildlife Service, Colorado Division of Wildlife and Trout Unlimited also are concerned about flow levels and fish habitat through the Black Canyon. At certain dates, the DOW has requested that flows be limited to improve the characteristics of a popular recreational fishery downstream. The Fish and Wildlife Service has requested that flows be increased at certain times to aid in the spawning cycle of native fish species, and the angling community, with Trout Unlimited, has requested that the Black Canyon receive “flushing” flows at least once in order to remove sediment that has built up in the river.
There was some skepticism on the UGRWCD board about whether the heavy releases were necessary this early in the spring.
Board member Steve Glazer said the Bureau has a bad record of accurately predicting runoff for the Gunnison Basin, and said this year was shaping up to be no different. Glazer said the river flow models were based on wet spring conditions, but “We are not having a wet spring.”
Spann agreed and said not as much water was running into Blue Mesa as expected because many of the low-lying hills and lands surrounding the reservoir were already dry. “A lot of the lower country has dried off much faster… The inflows are still not where (the Bureau) thought they’d be,” Spann said. Furthermore, Spann said, the weather in late April was cold and did not increase runoff.
Board member Gary Hausler believed a large portion of the predicted runoff was being absorbed and turning into groundwater.
Kugel said the runoff wasn’t occurring as predicted, but local snow packs were decreasing steadily. At press time, the snow pack in the Gunnison Basin was holding 130 percent of the average water content. Kugel said, “Three weeks ago we were above the 1984 level—now we’re below the 1994 level. It’s a significant drop-off.”
Kugel said the declining snow conditions should alleviate local high-water concerns. He said Gunnison has laid sandbags in a low section of town by the river and the Gunnison Living Community facility. “Hopefully those sandbags won’t be needed this year and they can be stored,” Kugel said.
The UGRWCD is also keeping a close eye on the Meridian Lake Reservoir, which the district owns as a supply of augmentation water. Augmentation water can be bought by other water users who run out of water or who are affected by a “call”—a situation where one water user has priority over another.
Kugel visited the reservoir a few days before the meeting, noting it was 94 percent full. However, he said, the measuring meter was several feet under snow and he would be monitoring the reservoir for an expected spill.
Glazer asked, “Will this be the first time it spilled since they constructed it?” referring to an overhaul of the dam completed in 2005.
Kugel said it would be the first spill, but that’s good news because once the rebuilt reservoir is proven to handle spills safely, the UGRWCD’s insurance rates will go down.
You can learn more about Blue Mesa and river flows at the District’s website: UGRWCD.org, under the “Current Hydrological Information” tab. (Note: There is no WWW in the web address.)