CHELAN — White-water kayak events through the exhilarating but short Chelan River Gorge will become a once yearly rather than four-times yearly event as interest among expert boaters has declined, Chelan County PUD commissioners learned Monday.

A plan developed jointly by the PUD and American Whitewater, a river-recreation advocacy group, will limit releases of water from Lake Chelan through the gorge to a single weekend a year.

The PUD and American Whitewater hope the once-a-year event will lead to a more consistent kayaker turnout. This year the water release will be the weekend of Sept. 15 and 16.

Only about a quarter-mile long, but treacherous with Class 4, 5 and 6 whitewater during spill events, the gorge is navigable only by expert boaters. Minimum year-round flow is 80 cubic feet per second.

The PUD’s federal license to operate Lake Chelan Dam originally ordered four annual releases of water through the gorge for white-water recreation, two in July and two in September. The change comes after a 3-year study revealed not enough interest among boaters to justify four events.

In July, too many other Northwest rivers were alluring to kayakers, said Thomas O’Keefe, Pacific Northwest stewardship director for American Whitewater.

And even if enough kayakers showed up to run the gorge, Lake Chelan water levels were sometimes low enough in mid summer that it was impossible to release water, said Michelle Smith, license and environmental compliance manager at the PUD.

The feds approved the new plan July 16. With the new plan, the water will be released on Sept. 15 and 16 no matter how many kayakers participate, whereas with the old plan, more than six people had to participate to justify releasing the water, O’Keefe said. He said most kayakers aren’t worried about missing extra weekends on the river.

“I think I had one person complain, who had done it every weekend,” he said. “The majority of folks felt that one weekend a year was the appropriate amount.”

For the Sept. 15-16 weekend event, flow will be increased to 375 cfs Saturday and 400 cfs Sunday. Boaters must register by 5 p.m. this Friday, sign a liability waiver and be approved by American Whitewater, which oversees the gorge runs, the PUD said in a news release.