If these 2 things happen, we might get to float the Boise River next weekend

The U.S. Bureau of Reclamation expects to drop the level of the Boise River below the magic number for what Ada County considers safe for widespread raft and tube floating next week, Peter Cooper, a civil engineer for the Bureau, said Thursday afternoon.

Meanwhile, the Boise Fire Department’s Dive Rescue Team has cleared most of the downed trees, brush and other debris that are most dangerous to floaters from the stretch of river between Barber Park and Ann Morrison Park. The crew could remove enough hazards by next weekend to make floating the river reasonably safe, fire department spokeswoman Char Jackson said.

If both things occur, Ada County could green-light raft and tube rentals at Barber Park, signaling the beginning of float season at a much later date than usual.

The county won’t begin rentals until the level of the Boise River is below 1,500 cubic feet per second, as measured at a stream gauge near the Glenwood Bridge. That’s a level at which most inexperienced floaters can safely negotiate the Barber Park-Ann Morrison Park trip on an innertube.

The river was at 1,800 cfs Thursday afternoon, as it has been since early July.

Reclamation plans to gradually reduce the amount of water it releases from Lucky Peak Reservoir, which controls the level of the Boise River, starting the middle of next week, Cooper said. By the end of next week, he said, the level should drop to around 1,000 cfs — well below Ada County’s threshold for floating.

Why it might still not happen

But there’s no guarantee float season will start next week, even if the river drops to 1,000 cfs.

The county also wants to make sure the river is free of as much debris as possible before it opens floating season. While it appears the Boise Fire Department has made good progress toward that goal, the Dive Rescue Team still could find debris that takes more time than expected to remove.

One complication is a telecommunications cable that crews discovered a few feet below the surface of the river near the Broadway Bridge. Jackson said the city is still monitoring the cable for now to determine if it’s a hazard worthy of action.

Jackson cautioned people not to jump the gun on floating the river. Crews might still be in the water over the next week, and floaters could put themselves and the dive team in danger.

‘Flow augmentation’

At least bureau officials sound confident about the prediction that flows will drop. The agency is confident it will meet its “flow augmentation” goal for the year, said John Roache, manager of the River and Reservoir Operations Group for the agency’s Pacific Northwest Regional Office in Boise.

Every year, Roache said, Reclamation aims to release 487,000 acre-feet of water from Idaho waterways above the demand of other uses like irrigation. This “flow augmentation” water is designed to help migrating fish downstream reach the Pacific Ocean.

The agency kept flows higher than normal this month in order to meet that obligation, even though it had plenty of room in its reservoirs to absorb runoff from major precipitation, Roache said.

The amount of water the agency can release changes based on snowpack and runoff. If the agency can’t reach the larger flow augmentation target, it tries for at least 427,000 acre-feet. If that’s not possible, it simply sends as much water downstream as it can without harming irrigation or other interests, Roache said.

In 2001, an unusually dry year, Idaho waterways contributed only 90,000 acre-feet to flow augmentation, Roache said.

This story was originally published July 20, 2017 at 4:35 PM with the headline "If these 2 things happen, we might get to float the Boise River next weekend."