#Monsoon2022 [is an] aid in soil moisture; not enough to impact basin-wide #drought conditions — The #ColoradoRiver District #COriver #aridification

Arizona monsoon cloud with lightning striking the beautiful Sonoran desert in North Scottsdale. Photo by James Bo Insogna. Title: Arizona Monsoon Thunderstorm. Taken on August 15, 2016. Used under a Creative Commons license.

From the Colorado River District newsletter:

Don Meyer, Sr. Water Resource Specialist, and Dave “DK” Kanzer, Director of Science and Interstate Matters, gave a thorough hydrological report to the Board on July 20th. Their report focused on the current, productive monsoon cycle, storage in local reservoirs, and the low flows and high water temperatures observed in the Upper Colorado River headwaters.

Monsoons

“We’ve been enjoying some moisture from this monsoonal flume,” said Meyer. “It seems almost weekly.”

These frequent, often fast-moving bouts of moisture have improved soil moisture across the District and helped farmers and ranchers by also providing cloud cover which decreases evaporation and soil temperature.

“Is it helping with the overall drought conditions?” Kanzer asked. “Well, the answer is sort of. It’s not doing much for the Colorado River Basin system as a whole, but those afternoon rain showers have done wonders for our local water users.”

Reservoir Storage

Wet and cool conditions in April sustained the snowpack which also helped local reservoirs with water storage.

“The longer runoff is delayed, the more water ends up in the system,” Meyer said. “However, we are still below average.”

Water managers across the West Slope depend on higher flows during the spring runoff to fill reservoirs for release during hotter, drier months later in the summer. Healthy river ecosystems depend on high flows to flush sediment, however, so often larger amounts of water are passed during the natural runoff window to support fish health. Choosing how much and when to fill a reservoir of any size involves accounting for myriad variables. Accurate predictions and streamflow forecasts are an essential part of getting this balancing act right.

Meyer shared how Elkhead Reservoir, one of the two reservoirs managed by the River District, was a study in this complex process this summer. “Elkhead fill was a bit of a nail-biter this year.” Meyer said. “We were operating to reduce downstream erosion. To do this we try to store peak flows and release a lower, steadier amount of water, but we had some issue with the forecasts. In early May, we realized that we weren’t going to get those big, forecasted peaks, so we had to quickly reduce releases. Incorrect forecasts were really detrimental.”

No forecasts for streamflow or storage on the West Slope are above 80% for this summer.

“We often talk about the importance of accurate science and forecasts,” said Andy Mueller, General Manager of the River District. “Not having accurate data does have major impacts for the health of streamflow and the human communities.”

Director Kathleen Curry from Gunnison County shared the dire conditions facing Blue Mesa Reservoir which is barely half full after last year’s Drought Operations release to Lake Powell and this year’s unimpressive runoff.

“The whole system is really stressed.” Curry said. “Blue Mesa is filled with algae, and the river above that is warm and bright green. The fish from the 15-mile reach are so stressed, they are coming up the Gunnison to just below the Redlands Canal. It’s become very difficult for the system to meet all the needs.”

The 15-mile reach is a section of the Colorado River where streamflow in the summer is reduced by more than half due to agriculture and municipal diversions in Grand Valley.

High Water Temperatures

“This is a tale of two years,” said Meyer “In 2021, we had some really hot, unusual temperatures. Last year it was in June, and this year, they were just as bad, but came later in July.”

In mid-July, temperatures in the Colorado River between Kremmling and Catamount (two USGS gages which provide data on streamflow, water temperature, dissolved oxygen and particulate matter) indicated that the water temperature was well outside a healthy range for fish. In response to the spiking temperatures, Colorado Parks and Wildlife issued multiple voluntary fishing closures not only for stretches of the Upper Colorado River, but also for sections of the Eagle, Roaring Fork, Fraser, and Yampa Rivers to protect already-stressed, cold-water fish like trout.

Wolford Mountain Reserovir, and the Gore Range. Photo: Brent Gardner-Smith/Aspen Journalism

Anticipating these conditions, the Colorado River District chose to release approximately 200 acre-feet of water from Wolford Mountain Reservoir. The low streamflow conditions are due in part to climate change and earlier, hotter summer temperatures, inaccurate streamflow forecasts, and trans-basin diverters who continue to fill their reservoirs regardless of the hydrological conditions on the Western Slope.

“The issue is not our ag producers,” said Andy Mueller, General Manager of the River District. “The issue is that Front Range diverters continue to take their water no matter what the snowpack looks like. Streamflow drops, raising the temperature of the river and damaging the fish health and the economy of the West Slope.”

Marc Catlin, Director from Montrose County shared his perspective as well. “There is no one at this table who is doing as well as they are. They divert 100% of their right now matter what, no matter what the snowpack.”

According to Brendan Langenhuizen, Director of Technical Advocacy, local anglers and residents of Grand County were deeply appreciative of the District’s efforts to lower water temperatures. “I’ve received several voicemails. One was from an angler in the Vail Valley. He talked about the real economic impacts due to high water temperatures. Once the fishing closures go into place, they can’t run their business.”

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