Flood concerns rise with additional Boysen discharge, mountain runoff

Flood concerns rise with additional  Boysen discharge, mountain runoff
By Nathan Oster
At a time of unprecedented flooding in and around Yellowstone National Park, Big Horn County officials are keeping a close eye on their own rivers and creeks which have risen in recent days due the release of additional water from Boysen Reservoir and a rapid melting of late-spring mountain snow.
Sheriff Ken Blackburn and Emergency Management Coordinator LaRae Dobbs said some lowland flooding could occur in the next few days and urged county residents to be both careful and proactive about moving their livestock and equipment to higher ground.
The Bureau of Reclamation announced Monday it would be gradually increasing the discharge from Boysen Reservoir from 2,300 cubic feet per second (cfs) to 6,000 cfs as a way of managing the reservoir level during the high runoff period. 
The increase was to occur in stages, reaching 6,000 cfs by 5 p.m. Tuesday, June 14.
In addition to the additional water from Boysen, the Big Horn River also collects water from various tributaries such as the Greybull and Nowood rivers as well as Shell Creek, all of which are impacted by mountain runoff.
Dobbs said what’s happening in and around Yellowstone likely won’t occur here and downplayed Snowtel data from the NRCS. “Those percentages give you a skewed view of what we have for snow water equivalent in the mountains,” she said. “It shows the Big Horn Basin drainage being over 3,000 percent of normal, but that’s because normally at Snowtel sites, what you have this time of year is zero.
“We’re about 10 days behind normal of when the snowpack comes down (with respect to Shell Creek),” she said. “Yes, there’s still some chance of lowland flooding, and the high temps in our forecast will bring (what’s left of the snowpack) down pretty quickly, but we’ve seen that happen before.”  Dobbs estimated the SWE at about 7 inches, “which is about what we normally have around June 3 or June 4.”
As of Tuesday afternoon, the county “wasn’t in a red alert stage by any means,” she said. On Monday, water levels around Hyattville reached flood stage and Shell Creek nearly reached “action” stage, but both subsided and that was still the case on Tuesday.
“People need to realize how quickly water levels can change when snowpack is coming down, along with the high temps,” she said. “When water’s moving that fast, the force behind it is very dangerous and people need to respect those waterways.”
Meanwhile in Greybull, the town’s emergency management director, Paul Thur, has been keeping a close watch on the Big Horn River.  On Monday, it was at 87.1 feet, its highest point since June of 2019. By evening, it had reached 87.4 feet before dropping to 87.35 Tuesday morning.
The town considers 90 to be “action” level, so the river is still a bit below that, Thur said.