Supermelt flooding faces Top of Utah

May 27 2011 - 11:06pm

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OGDEN -- Pineview Reservoir will overflow sometime during this year's spring runoff, the director of the Weber Basin Water Conservancy district said Thursday.

The only questions are when and how much.

Nothing is certain except that the amounts of water going into the reservoir, and how much can safely be let out, make spilling inevitable. There is six times as much water waiting to melt down into Pineview as the reservoir has room left to hold.

If Pineview were bone dry, the water waiting to come down would fill it. If all that water comes down too quickly, the reservoir will spill.

The snowmelt is going to come down too quickly. The runoff was supposed to start in April but hasn't begun yet, and every day the weather stays cold and wet makes the delay worse.

And it's not just Pineview.

This spring, every reservoir operated by the district is being asked to hold back more water than it was designed to hold. Preventing those reservoirs from overflowing, which would cause uncontrolled flooding along the rivers below those reservoirs, is the district's job.

To visualize what District Director Tage Flint faces, imagine filling a jug with water from a very large bucket by pouring it through a very narrow funnel.

The bucket is huge. If you pour too fast, the tiny funnel fills up and water sloshes out of it and onto the floor.

Now imagine, also, you can't control how fast the water pours out of your bucket. As you watch, more and more water pours into your funnel, faster and faster.

Still, you must, somehow, try to keep the water in the funnel from sloshing out onto the floor.

Oh, yeah, and you can't let the jug overflow, either.

In Tage Flint's world, the funnel is a reservoir, the jug is the Weber and Ogden rivers, and the ever-overflowing bucket is the Wasatch Mountain snowpack, which, any day now, is going to unleash so much water that Flint is scared.

He's got eight reservoirs catching melted snow and feeding it into the Weber and Ogden rivers. His job is to hold back as much water as he can so it doesn't flood Weber County.

At the same time, he has to release enough water from his reservoirs to keep those reservoirs from overflowing. If they overflow -- they have spillways, so the water won't actually go over their tops -- he loses control of the rivers.

Flint said nobody has seen a snowpack and weather situation like this year's. Huge piles of snow have built up, double what is normal. A cold, wet spring has kept the snow up there and even added to it. Instead of a long, slow melt and runoff, Utah is looking at a short, hot and quick melt.

The later into May and June it gets before the snow does melt, the worse the flooding situation gets, and it's already ugly.

"We're off the map. These are uncharted areas for us," Flint said Thursday, "and we're sure, in some cases, the infrastructure cannot deal with the runoff and keep everybody from flooding."

His reservoirs were built in the 1950s for water supply and drought relief. They can be used for flood control "as they can handle it," Flint said, but that is a secondary purpose. They were not built to handle a "worst-case" scenario like this year.

The reservoirs are helping. If all the reservoirs on the Weber River disappeared today, Flint said, the river flow in western Weber County would be 8,000 cubic feet per second, double what it is now.

But his reservoirs are filling up. Even if all his reservoirs were bone dry, this year's snowpack would fill them up, some several times.

The district has been releasing water as quickly as it can, but "what hurt us the worst is the last two weeks with rain," Flint said. "It just killed us. It filled up the space we were saving for the runoff."

Causey Reservoir, east of Pineview Reservoir, is already spilling, and people along the South Fork of the Ogden River are being flooded.

Pineview Reservoir can hold 110,149 acre-feet of water. As of Thursday, and despite Flint's best efforts to lower it, Pineview had 91,423 acre-feet of water, leaving just 18,726 acre-feet to fill.

The National Weather Service says the snowpack still sitting in Pineview's drainage area holds 116,734 acre-feet.

Pineview will spill, Flint said.

"We've stepped up releases from Pineview because we know the peak has not even come close to hitting it yet," he said. "We are hopeful we will get through the peak (of the runoff) before we spill it, and we're trying to stretch Pineview at least two weeks before it spills."

The major reservoir controlling the Weber River is Echo, near Coalville. The numbers on it are scarier.

Echo Reservoir holds 73,940 acre-feet of water. As of Thursday, it had 49,539 acre-feet, leaving 24,400 acre-feet of room.

That sounds like a lot, but the snowmelt projected to come down to it is 232,743 acre-feet, three times the reservoir's capacity.

Flint said he is juggling releases from Echo and Pineview, trying to control the runoff enough to prevent serious flooding down the Ogden and Weber rivers.

But there are no guarantees, he said. If both reservoirs spill at the same time, it will be ugly. Ultimately, the weather will decide.

Flint said his ideal would be moderate temperatures starting today, with highs in the 70s and cooling down at night. That would allow the snow to melt in pulses, a bit at a time, letting him catch and release the water in his reservoirs while keeping their levels below spilling.

"That's the name of the game, to peak before we spill."

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