Emergency Management releases information on runoff

We are approaching the end of the winter season with the first day of Spring just around the corner on Monday, March 20. In many places, Thermopolis and Hot Springs County is still covered in a blanket of snow that, thanks to high temperatures in the 40s on Monday, Tuesday and Wednesday of this week, is beginning to melt. As the melting of this massive amount of snow takes place, citizens are dealing with runoff near their homes.

Although sand bags and sand is available at Hot Springs County Road and Bridge, in most cases of yard snowmelt, sandbags are not going to be overly effective. Moving snow away from your house and digging channels in the snow to direct the melt flow is the most effective way to help the situation.

As we navigate through spring, making the extra effort to keep runoff away from our homes is something most everyone will be dealing with.

A local source for additional information is Hot Springs County Emergency Management Coordinator, Bill Gordon. He can be reached at 864-4649 or by email at bgordon@hscounty.com

Regarding runoff, Gordon has issued information and history on Hot Springs County River and Stream Awareness Levels. This information will really come in handy this year with overall projected high runoff amounts. It may not be something we have not seen before, it will just most likely be higher than in recent years.

After a high snowmelt runoff year in 2017, the Hot Springs County River and Stream Awareness Levels were developed by Hot Springs County Emergency Management in 2018 to help provide the public with a means to monitor river and stream flow status, helping them make decisions for their own safety and be better prepared.

The current Awareness Level is posted each week in the Thermopolis Independent Record. Whenever the Awareness Level Changes the Independent Record publishes an article explaining what conditions exist that warranted the change.

River information

The Wind River flows from The Wind River Mountains into Boysen Reservoir, then north through the Wind River Canyon. It becomes known as the Bighorn River at a spot known as The Wedding of the Waters, a few miles south of Thermopolis.

Boysen Dam was built around 1950 for electric generation, irrigation, recreation and flood control. Prior to the dam, spring runoff would sometimes completely flood the Thermopolis downtown area, with flows reaching 20,000 to 30,000 cubic feet/second (cfs). After the Boysen Dam was built, spring runoff from the mountains could be corralled.

With the increase in residents, tourists, whitewater users and fishing guides using the Bighorn River in Hot Springs County it became important to provide a means of informing the public, particularly the inexperienced, amateurs and tourists of the danger posed during a big snowmelt runoff year.

The Bighorn flow in the winter might be 900cfs. In a typical summer, depending on calls for irrigation water, the flow might be 1,500 – 2,500cfs,.

In some years, a 24-hour flushing flow is performed for Wyoming Game and Fish to improve fish habitat. The river typically peaks at 5,000cfs for a 12-hour period before returning to the previous flow. These flushing flows are well announced across the county.

According to Gordon, in a high snowmelt year everything changes. The highest runoff Boysen Dam releases down river have been 11,000 -12,000cfs. Though mostly contained in the river banks and with minimal flooding in low lying areas, such flows are incredibly powerful and can be deadly. A typical high runoff year might involve releases in the 8,000-9,000cfs range. Flows leading up two this level can be deadly as well. So, as snowmelt runoff begins certain thresholds were developed for river awareness.

This period typically runs from April or May through late July or early August. As snowmelt runoff begins entering Boysen Reservoir, releases are calculated by the U.S. Bureau of Reclamation (USBOR) Casper Control Center which accommodate inflows and adjust releases in order to have the lake exactly or close to full when the runoff ends. USBOR notifies County Emergency Management whenever flow adjustments are made.

“Please note here, USBOR is very good at what they do. This process triggers Hot Springs County’s River Awareness threshold release rates, 3,000, 5,000, 7,000, 8,500fcs,” said Gordon.

Newspaper, social media and county CodeRED messaging along with river launch area signage is implemented to raise awareness and help inform those who might not know the risks involved in floating the river at various flows and the need for Personal Flotation Devices (PFD) and eventually the need to consider not getting on the river unless experienced or floating with a professional. The signs are placed at five common launch areas along the river and changed as thresholds increase. At 8,500cfs, a large sign is hung on the Thermopolis Eighth Street Bridge to advise floaters to exit at that boat ramp access because at that level the next bridge downriver does not allow space to pass underneath.

Creek information

Several stream drainages run across Hot Springs County into the Bighorn River. The more prominent are Owl Creek, Grass Creek, Cottonwood Creek, Gooseberry Creek, Kirby Creek and Buffalo Creek.

Certainly the largest drainage system is Owl Creek. There are four major forks of Owl Creek. These forks come down from the Absaroka Range at the west end of the county, draining over 256 square miles of rugged mountains and valleys. South Fork flows into Anchor Dam. The others (North Fork, South Fork of North Fork and Middle Fork) converge into South Fork between Anchor Dam and the Hwy. 170 bridge at Arapahoe Ranch. When snowmelt is coming out or strong thunderstorms are crossing the drainage, flooding can occur downstream on the lower sections of Owl Creek.

Grass Creek, Cottonwood Creek and Gooseberry Creek drain large areas in the west end of the county and can also flood, though these streams are more sparsely populated.

Kirby Creek and Buffalo Creek drain high country in the east end of Hot Springs County. Large rain events or strong thunderstorms, particularly on already saturated soils can cause flooding on Kirby Creek as it nears the Bighorn River near Lucerne. Buffalo Creek can also flood for the same reason.

Spring Creek has caused problems for East Thermopolis and Red Creek is always a topic of conversation when it turns the Bighorn River a muddy red when it floods.

The Independent Record will update on runoff flows and risks involved as the season progresses.