Reservoirs low, but NOAA forecasts snow

The volume of water flowing into local reservoirs was below normal last month, but northern Wyoming might be in for favorable snowpack this winter.

Inflow into Buffalo Bill Reservoir during September was 15,500 acre-feet. That is 63 percent of the September average (24,600 acre-feet) based on the 1985-2014 period, according to Bureau of Reclamation tables.

However, Buffalo Bill’s accumulation through the water year was 892,900 acre-feet. The average is 853,600 acre-feet, putting 2015 at 105 percent of average.     

The water year runs Oct. 1 of the previous year to Sept. 30 of the present year, or in this scenario, Oct. 1, 2014 to Sept. 30, 2015.

Buffalo Bill is nearly 64 percent full. Outflow was 916.8 cubic feet per second (cfs) last week.

Buffalo Bill autumn outflow fluctuates from year to year, said Mahonri Williams, Reclamation chief of resource management division in the Wyoming area office in Mills.

If it is cold and wet, outflow will be less. If it is warm and dry, like this fall, outflow is higher to meet greater irrigation demands.

Shoshone Irrigation District closed the Garland Canal Sunday, Oct. 18. Willwood Irrigation District turned its water off Thursday, Oct. 15. Heart Mountain Irrigation shut down Oct. 20, Williams said. “So that’s when we’ll go to our winter flow.”

Winter flow started Sunday with 200 cfs from Buffalo Bill Dam. From the dam flowing downstream, the Shoshone River will pick up another 60 cfs from springs before reaching Cody, Williams said.

Boysen Reservoir’s September inflow was 32,100 acre-feet. The average is 47,600 acre-feet, so Boysen is 67 percent of average. But, Boysen had a good water year with 1.44 million acre-feet, compared to the average of 895,900 acre-feet to make the water year 128 percent above average.

Boysen was releasing nearly 824 cfs as of Oct. 15.

Boysen will continue to release 824 cfs this winter to generate power and maintain the reservoir’s water level, Williams said.

“Streamflows into Big Horn Lake during September were 83 percent of average,” said Clayton R. Jordan, Bureau of Reclamation Reservoir and River Operations, in an Oct. 2 report.

Based on the Oct. 1 water supply forecast and the planned releases out of Boysen and Buffalo Bill reservoirs, the October runoff into Big Horn Lake is expected to equal 136,300 acre-feet (86 percent of average), the report said.

Big Horn Lake was nearly 95 percent full as of Oct. 15. Outflow was 2,472.5 cubic feet per second (cfs).

“We set our winter release the first part of November,” Jordan said Friday.

Reclamation will hold a meeting in Billings on Nov. 5 to discuss the 2015 water year and 2016’s water outlook, Jordan said. However, the winter outflow will probably be between 2,400-2,500 cfs, which is pretty close to the 30-year average winter release.

The Shoshone River flows into Big Horn Lake. From Yellowtail Dam, Big Horn River resumes its journey north to join the Yellowstone River.

El Niño may not have much say around these parts, but northern Wyoming may be in for a snowy winter.

“Sea surface temperatures across the equatorial Pacific have been near average since spring 2012, and forecasters expect that to continue through the winter,” according to the National Oceanic and Atmospheric Administration (NOAA). “This means that neither El Niño nor La Niña is expected to influence the climate during the upcoming winter.”

The precipitation outlook favors above-average precipitation in the Northern Rockies, particularly over Montana and northern Wyoming and in Hawaii, NOAA said.

However, light jackets in the mornings and T-shirts in the afternoon are still in style for now.

The high temperature Thursday (today) is forecast to reach about 64 degrees in Powell, and a low of about 43 degrees, according to the National Weather Service.

There is a 20 percent chance of showers tonight and Friday. Friday’s high is predicted to be about 57 degrees and the low, about 34 degrees.

Saturday’s high is expected to be 61, and the low, 36 degrees.

What happens downstream can have an effect on those living upstream. So Wyoming residents would be wise to keep an eye on the consistently dropping water levels at Lake Mead and Lake Powell — the water-power source for the Hoover Dam.

Water levels have been dropping for more than 15 years, reaching historic lows during the water year that ended on Sept. 30.

According the U.S. Bureau of Reclamation, Lake Mead’s water levels were at 1,078.1 feet (38 percent full) at the end of September. This is the lowest the lake has been since it was still filling up in early 1937.

The highest the lake’s water levels have been was in the summer of 1983 when elevations exceeded 1,225 feet. Water levels have fluctuated a bit since then, but have dropped consistently since 1999 or 2000.

The lowest the lake has ever been since it completed filling was in late June of this year when levels were at 1,074.71 feet.

Prior to recent upgrades to its turbines, the Hoover Dam needed 1,050 feet of water to function — a milestone water level that would be surpassed within 12-18 months, given recent rates of drainage. Now the dam can function with 950 feet of water in the lake, so there’s about 128 feet to go, and it took about 15 years for the water levels to drop that much.

Lake Powell is essentially the back-up fuel tank for the Hoover Dam — when Lake Mead gets too low, then Lake Powell picks up the slack.

Meanwhile, Lake Powell is 93.89 feet below full pool (3,700 feet) with an elevation of 3,606.11 feet — which is 50.75 percent of full at its current 24.3 million acre-feet. The lowest Lake Powell has ever been was in the spring of 2005 when it was 3,555.1 feet and the highest was in the summer of 1983 when it reached 3,708 feet.

“We are watching levels closely, because this is one basin that has not come out of the drought, while others have,” said Wyoming state engineer Pat Tyrrell. “One snowy and cold winter can do a lot for that basin.”

The primary concern is the ability to continue generating hydro-electric power, he said.

Wyoming is not currently looking at changing any water rights. Discussions between the state and federal government so far have focused on how to extend operations, Tyrrell said. Right now, the upper and lower Colorado River basins are looking at draft contingency planning, should drought conditions continue and water levels drop further.

“There is a definite desire to watch the levels and do what we can to protect those reservoirs,” Tyrrell said.

Wyoming’s Green River Basin is one of several water sources for the Colorado River through Flaming Gorge Reservoir, so a possible route would be to adjust those upper river reservoirs to keep Lake Mead at a functioning level, Tyrrell said.

Other possible steps include water demand management and having people upstream voluntarily reduce their water usage. Trials with weather modification have proven successful with cloud seeding, so there is also interest in expanding that work, Tyrrell said.

Wyoming’s legislators approved continuing the previous cloud seeding program and expanding it into the Big Horns and Laramie area, Tyrrell said.

“We are looking at different ways to address the shortage of water in that basin,” Tyrrell said.

A pilot program was done over the summer with volunteer projects in Wyoming and Colorado to see if the water demand management approach could work.

The main goal is for the states and the federal government to get through the drought without making any litigation, Tyrrell said.

“We certainly are trying our darnedest to avoid draconian measures and litigation, because nobody wins in that environment, and every state wants to make them (mitigation measures) work,” Tyrrell said.

The 1922 Colorado River Water Compact requires the upper basin states to not deplete the river to where they can’t send 7.5 million acre-feet per year on average over 10 years.

“The bigger concern is, can the upper basin states continue sending enough water?” said Harry LaBlonde, director of the Wyoming Water Development Office. If the compact is violated, then there will be impacts in Wyoming. “We would have to curtail water usage to meet that obligation.”

Currently the lower water levels at Lake Mead and Lake Powell are not affecting Wyoming’s water — but there are concerns, LaBlonde said.

Most of Wyoming’s contributions to the Colorado River go through Flaming Gorge, which is largely fed by the western portions of the state, such as the Green River.

Flaming Gorge currently is releasing a daily average of 1,700 cubic feet per second and is about 91 percent full, according to the Bureau of Reclamation.

“We had a very good spring that filled reservoirs around the state,” LaBlonde said.

Locally, water from the Big Horn Basin flows into Montana and ultimately into the Missouri River. Unlike the Colorado River compact, not all of the states within the Missouri River drainage are combined in a compact agreement for maintaining water levels downstream.

But the Missouri River is doing fine, thanks to plenty of rainfall during the summer for the North Platte and other regions, Tyrrell said.

Spring weather is what determines snowpack runoff, so a winter with 150 percent snowpack does not guarantee a 150 percent inflow downstream, Tyrrell said.

“The West in general is doing all right, and Wyoming had a good 2015 — and for 2016 we will see what the winter brings,” Tyrell said. “We are very reliant on winter snows.”