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Jeffrey D. Allred, Deseret News
Sandy City Utilities workers install muscle wall to Little Willow Creek in anticipation of flooding in Sandy Thursday, May 5, 2011.

WEST JORDAN — With more snow or rain expected to come late Sunday into early next week, the good news is that Utah's water supply is beyond anyone's expectations.

The bad news is that water still has to come out of the mountains.

"For those of you praying for water, knock it off," Randy Julander chided Thursday during a meeting of the Utah Water Users Association.

It's been stressed before and it was stressed again at this monthly meeting that flooding is looming for many areas of the state, and Julander warned that mud and debris flows are probable.

"Staggering" is how the association's executive director Carly Burton described the numbers quantifying the amount of snow still left to melt in the state's watersheds.

A colder than normal April with precipitation 200 percent of normal did not only pause any snowmelt, but added to already overwhelming levels of snow in the mountains.

Julander said 2 feet of fresh powder was measured at Trial Lake above Kamas Valley on May 1 after the most recent storm. And overall, in northern Utah, that low-elevation snow is anywhere from 50 percent to 200 percent or even 300 percent more than what existed on the ground in the big flood year of 1983, Julander said.

"Hang on," he told the group of water managers crowded in the meeting room of the Jordan Valley Water Conservancy District offices. "It is going to be a fun ride for the next six weeks and you are going to be lucky to hang on."

At the meeting, snowpack information, flooding hot spots and reservoir capacity details were released, including:

The U.S. Bureau of Reclamation and emergency managers are warning residents in Jensen, Randlett, east of Roosevelt, and Green River that flooding is imminent. A 7 p.m. meeting for residents is scheduled for May 12 at the Western Park Convention Center in Vernal. The Green River, infused with the rushing waters of Colorado's Yampa River, is expected to fill farm fields and damage homes. The Yampa is expected to be 6 to 10 feet above its peak levels.

The estimated inflow into Lake Powell has jumped by 2 million acre-feet of water in just one week, leading the Bureau of Reclamation to revise its estimates on how much the lake will rise. Overall, Lake Powell will receive 11.5 million acre feet because of runoff. Initially thought to fill 10 feet higher, the lake will rise by as much as 25 feet. The BOR's Ed Vidmar said over the next four to six months, as much water will be released as possible downstream to Nevada's Lake Mead, and the power plant will run at full capacity. The excess water, he noted, is good news for the Colorado River Basin and for Lake Powell recreationers, with the lake being 45 feet from full by sometime in July.

Utah's reservoirs will be enormously challenged to ease the pressure off rivers and creeks and control flooding. "There's a lot of water and reservoirs are not going to be the saving grace," Vidmar said. "We will do all we can."

The bureau's numbers, for example, show that Causey Reservoir has a storage capacity of 7,070 acre feet, but it is forecast to receive 93,000 acre feet, and that is a conservative number, Vidmar said. Echo has even scarier numbers to confront, with a 74,000 acre feet capacity that is predicted to have to take in at least 340,000 acre feet. "What do you do with all that water?" Vidmar asked.

Julander noted that the inflow into Bear Lake in April was 132,000 acre feet — which is as much water as Rockport and Echo combined. Bear Lake, he said, might just fill this year.

Water managers concede their ability to move so much water around is like playing a game of hot potato among different regions — reservoirs serve the purpose of capturing runoff and preserving water for storage, but dams can only hold so much as river banks reach flood stage.

The situation is unprecedented in some ways even beyond what was experienced in 1983, because this year's snowpack is substantially higher in many basin drainages.

The Bear River Basin is at 207 percent of normal, the Weber Basin is 214 percent of normal and the Six Creek Basin — or the mountains above the Salt Lake Valley — is 191 percent of normal.

With another round of storms due to hit late Sunday and linger into Wednesday bringing more water on top of snowmelt, the opportunity for Utahns to escape the season flood free is long gone.

"The margin of error is getting smaller and smaller," too, as the probability of a quick and drastic warm-up inches closer with each passing day, warned Brian McInerney, hydrologist with the National Weather Service in Salt Lake City.

Areas with the highest potential for wide-scale impacts include Cache County along the Logan and Blacksmith Fork rivers and urban waterways such as City Creek and Emigration will test the strength of culverts as they handle increased flows. Big and Little Cottonwood creeks will be challenged, with flooding memories still fresh from 2010 when snowpack was not nearly as substantial.

McInerney said anyone who lives along a waterway should take special heed, prepare for floods and exercise extreme caution when it comes to children.

In 1997, he said, seven people died in waterways.

"We can replace our homes and stuff, but we can't replace our children."

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