#Drought news: West Slope reservoirs update

From The Grand Junction Daily Sentinel (Dennis Webb):

This low water year in western Colorado, part of a longer-term drought dating back nearly 20 years, is exposing not just onetime valuables, but also the vulnerabilities of the region to negative consequences when the snow and rain refuse to fall.

Beaches closed at reservoirs, and boat ramps were left high and dry. So were some irrigators, particularly ones with junior water rights who in some cases got essentially no irrigation water this year.

The first-ever call went out on the Yampa River, resulting in curtailment of water use by some water rights holders.

The water level at Blue Mesa Reservoir is at just 30 percent of capacity. It’s at 81 feet below full pool elevation. Nicki Gibney, an aquatic biologist with the National Park Service, said that’s the second-lowest ever since the reservoir first filled. She’s been dealing with one outcome of the low water levels — an outbreak of unsafe levels of cyanotoxins created by algae in the Iola Basin section of the reservoir. While it can harm humans, it’s a particular threat to dogs because of their propensity to drink water from lakes.

And never mind dogs. Try being an endangered fish this year on the 15-mile stretch between the irrigation diversion points in the Palisade area and the confluence of the Gunnison River downstream. Flows dipped below 200 cubic feet per second over almost a two-week period starting in late September, dropping as low as 150 cfs or so at times. Those are the kinds of flows more typically found on tributaries of tributaries of the Colorado River, rather than on the river itself. Water so low can kill off some of the aquatic insects on which fish rely, warms up to temperatures that stress the fish, and runs clearer than when the river is at higher levels, making the fish easier pickings for predators such as great blue herons…

HISTORIC LOWS

Storage in the Colorado River system, as calculated by the U.S. Bureau of Reclamation based on 10 reservoirs it operates, fell to 47 percent of capacity as of Oct. 1, from 55 percent last year. Oct. 1 is the annual start of another water year for the Colorado River system, as another snowpack season gets underway. In percentage terms, that’s the lowest storage level at the start of a water year since that system was fully built out and filled.

The Bureau of Reclamation says unregulated inflows to Lake Powell for the 2018 water year totaled 4.76 million acre-feet, or 44 percent of the 30-year average, making it the third-driest year on record. Unregulated inflows are calculated amounts designed to indicate what flows would be if not influenced by operations at upstream reservoirs.

The unregulated inflow into Lake Powell in September was a mere thousand acre-feet, the lowest on record. It’s so low that the Bureau of Reclamation rounds it off as being 0 percent of average. The second-lowest September unregulated inflows occurred in 2012 and totaled about 100,000 acre-feet.

The Bureau of Reclamation says unregulated inflows into Powell were above average just four out of the past 19 years. The reservoir’s storage is currently at 45 percent of capacity, and water officials in the Upper Colorado River Basin are hard at work pursuing drought contingency measures, potentially including measures to reduce demand, to keep Powell from falling too low. Should it empty too much further, that would threaten its ability to produce, and generate revenues from, hydropower, and to deliver water to downstream states to comply with a 1922 interstate compact.

FRAGILE SYSTEM

Hannah Holm, coordinator of the Hutchins Water Center at Colorado Mesa University, said the message she’s been hearing over and over this year is that reservoir storage enables western Colorado to get through one bad drought year like this one, “but if we get another one it’s going to be a totally different story.”

“… A lot of the reservoirs we have are not really enough to help us weather two or three dry years. It just kind of brought home to me how fragile our whole system is, as far as our whole water management system.”

She said it’s pretty resilient on a year-to-year basis, but the question is how vulnerable it may be in the long term, particularly in light of forecasts suggesting a high likelihood of more and deeper droughts in the future, when higher temperatures are expected to exacerbate the problem.

Even this year, Holm said, it’s been “kind of eye-opening” to hear stories of irrigators basically getting no water in some areas.

“Never mind what their water rights are, there just wasn’t any water to take,” she said.

Alan Martellaro, division engineer for District 5, the Colorado River Basin district of the state Division of Water Resources, said if it wasn’t for upstream reservoir storage, things would have been “extremely bad” for water users on the mainstem of the river this year. But he said some water users on side tributaries where there wasn’t water storage experienced some pretty dire conditions.

Base flows in streams fell because there’s less groundwater to feed them. Low base flows also mean more pressure is placed on reservoirs to make up for that water.

“We’ve pretty much exhausted our storage supplies from Green Mountain and Ruedi (reservoirs) just to get through this summer. It’s going to be helpful to have just an average snowpack this winter to replenish this storage,” he said.

Martellaro said a number of streams had calls on them the entire irrigation season. On those streams there was never enough water to satisfy all water rights on any given day, and some owners of junior water rights never got water…

‘UNPRECEDENTED’ FOR YAMPA

“It was just an unprecedented year,” said Doug Monger, a Routt County rancher who also is a county commissioner and serves on the Colorado River District board.

After a winter with lower-than-average snow, the typical summer rains failed to come, and hot, blistering winds dried everything out, he said. The result was that first-ever call on the Yampa, which Monger said up to now has been regarded as a “free river.” He said the call served as a wake-up call. Many irrigators had never previously bothered to put in measuring and shutoff devices required for water rights to be administered based on the seniority of those rights. Monger said irrigators, himself included, realized they need to up their game in ditch operations and measuring and accounting for water use…

Klaus Wolter, a research scientist in Boulder with NOAA, said by email that he’s still trying to determine what the developing El Niño means for Colorado. He cautioned that El Niño winters are often dry in midwinter over the mountains, so the state can’t count on the favorable moist weather pattern that began this month to continue.

Still, he has seen wet falls often presage decent winter snowpacks, and said if the moister-than-normal conditions this fall keep going into December, “it will tilt the odds toward a good snowpack/runoff year.”

“Current indications are encouraging for above-normal moisture in November, so I am guardedly optimistic overall,” he said.

Reservoir operators, irrigators and municipal water suppliers will be watching snowpack levels closely this winter. According to the Natural Resources Conservation Service, as of the end of September, overall reservoir storage in Colorado was at 79 percent of average. That compares to 117 percent of average a year earlier. Colorado’s above-average storage levels over the last year ended up proving crucial in providing backup water for snow and rain that failed to fall.

While storage levels were 90 percent or more of average across the rest of the state as of Oct. 1, they were about half of average in the Gunnison River Basin and in far southwest Colorado.

Martellaro said an average snowpack would typically be enough to fill reservoirs such as Ruedi and Green Mountain in the Colorado River basin in Colorado, along with reservoirs on Grand Mesa.

It can take multiple years for depleted, larger reservoirs such as Blue Mesa to refill. For now, Gibney is keeping a close eye on the cyanotoxin problem resulting from the algae there. Gibney said blue-green algae has been documented at the reservoir since the 1970s. It produces cyanotoxins under certain conditions that aligned this year. Just what conditions are required is still a matter of research, she said…

Algae problems also have been an issue in recent years on the White River in Rio Blanco County. Colorado Parks and Wildlife spokesman Mike Porras said his agency has been looking into what is leading to algae growth there, and other factors may be behind it other than drought.

‘DISMAL’ YEAR FOR IMPERILED FISH

Meanwhile, Tom Chart, program director for the U.S. Fish and Wildlife Service’s Upper Colorado River Endangered Fish Recovery Program, is reflecting back on what he said has been a “dismal” year in terms of flows in that crucial river stretch below Palisade. The program seeks to protect the razorback sucker, humpback chub, bonytail and Colorado pikeminnow.

The program tries to keep average monthly flows on the 15-mile stretch above 810 cfs, more than four times the flows experienced at times this year. For a time the stretch benefited from extra water releases by the Colorado River District as it lowered its Wolford Mountain Reservoir to do dam work. After that, Chart said, the 15-mile stretch’s flows were basically reliant on releases from upstream reservoirs of dedicated “fish pool” water totaling about 200 cfs, but some of that water is lost in transit as it soaks into the riverbed upstream or evaporates.

Contributions of water by other entities, such as the Colorado Water Conservation Board and ExxonMobil subsidiary XTO Energy, helped supplement flows later in the season. Chart said if it wasn’t for a combination of initiatives, the stretch of river likely would go dry in a year like this one.

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