Plan ahead for major river flow increase

by Mark Dykes

The Bureau of Reclamation issued its forecast of the April through July runoff predicted for the Bighorn Basin.

According to the report, inflow to Boysen Reservoir is forecast to be 1,500,000 acre-feet (af), which is 278 percent of the 30-year average of 540,000 af. Approximately 132,800 af of the forecasted amount flowed into Boysen during April, leaving approximately 1,367,200 af of inflow forecasted for May through July.

Releases from Boysen Dam to the Wind River are scheduled to increase to 6,500 cubic feet per second (cfs) today, following a temporary decrease 3,000 cfs, to allow the Wyoming Department of Transportation to stabilize an embankment along Highway 20/789, near the Upper Campground.

County Emergency Management Coordinator Bill Gordon said the record inflow at the reservoir was in 1967, at 1.2 million af, which resulted in flows from the dam over 14,000 feet. The current inflow forecast for May through July of this year, Gordon said, is for 1.5 million af.

The maximum height for the reservoir, Gordon said, is 4,725 feet above sea level, and the level can be dropped to 4,700, which is the top of the spillway; this point is as low as it can go. The level was at 4,704 when it was apparent the release from the reservoir had to be reduced to allow for the work to stabilize the embankment near the Upper Campground. Gordon further added a geologist said the hill along the northbound side of the highway is sliding, and the work done this week is to help stabilize the hill prior to increased flows this summer.

Gordon said outflows from the reservoir are adjusted accordingly, depending on how fast the reservoir is filling, to prevent water from flowing over the top of the spillway gate. There is also the hope there will be a full reservoir by the time the inflows are done.

As to the increases, Gordon explained they will go up to 8,000 cfs beginning June 1, but will be increased as necessary. The increased flow could be startling, Gordon said, because it’s something not seen by most people; 1995 saw flows of 9,512 cfs, and 2010 saw flows of 7,308 cfs.

The town could see trouble if the flows reach the 10,000-12,000 range, but at this point Gordon had no information as to whether that will happen. At 8,000 cfs, he said, there will be some low-lying fields and river-adjacent properties that will see some water. The areas which will likely see water as the flows increase, Gordon said, are east of the railroad tracks, around South Second Street. There is the potential to see six inches to a foot, Gordon noted, but not water so high it will destroy homes.

Gordon wants to raise awareness now for those living along the river, that there is a potential for flooding. Because of the high flow numbers, he said, people would have to make a judgment call when it gets to that point and act accordingly. He added those who live in areas known for flooding might want to plan ahead now.

With regard to the inflow of to the reservoir, Gordon said the Popo Agie watershed, one of the most significant contributors of runoff, currently has anywhere from 31 to 33 inches of water. A meteorologist, he said, went up above the Loop Road on the middle fork of the Popo Agie, and reported there is 68 inches of snow up there, and approaching 34 inches of water.

There’s something of a “perfect storm” happening right now, Gordon said. There is increased snowpack and runoff, and he believes the canyon has reached a point of saturation where any additional moisture is going to cause more slides. As for the tributaries of Owl Creek, Cottonwood Creek, Gooseberry Creek and Kirby Creek, Gordon said on Tuesday that they’re already on flood watch, and with the forecasted rain and snow this week that alert could be upgraded.

Looking to stay ahead of the possible flooding, Gordon is asking for anyone interested in volunteering to fill or place sandbags. He would like to put together a list of contacts for when the time comes. He further noted he has available two sandbag machines, which can make 4,000 to 5,000 bags a day.

Gordon is also looking for anyone with wooden pallets to donate, as they will be used to stack sandbags on for ease of loading and transporting. Those who can provide either pallets or help in preparing sandbags can contact Gordon at 864-4649 or bgordon@hscounty.com. Gordon said building sandbags will happen at the end of the month, and he is looking to gather as many pallets as possible. Distribution points for sandbags have not yet been determined. These points will be announced when necessary.

The possibility of flooding is something being considered now, while there is time to prepare, Gordon said. He was on a conference call with the Bureau of Reclamation this week, and such calls will increase — possibly even to a daily basis — as we prepare the best we can.

The situation isn’t just one that impacts us this year, however. Gordon said because of the way things are going, if people are planning a trip they need to make looking at the forecast part of their regular routine in years to come. The slides in the canyon will take a long time to heal, Gordon said, to the point where the walls are stable again. Even when making small trips, say to Shoshoni or Riverton, people need to be aware of the weather, as any rain could potentially cause another road-closing slide.