Unseasonably high releases from Jackson Lake Dam will continue through at least Sept. 28 because irrigators halfway across Idaho are demanding water for hay, sugar beets and potatoes, a federal water manager and state official said Thursday.

Snake River flows usually drop in early September. But this year, with Palisades and American Falls reservoirs all but empty and downstream farmers still calling for water, the only available source — Jackson Lake at the base of the Tetons in a national park — is being tapped. The unprecedented releases of 4,500 cubic feet per second are flowing all the way to Milner, Idaho, where canals distribute the water to farmers.

“We’re waiting for a change in irrigation demand,” said Mike Beus, water operations manager for the Bureau of Reclamation’s Snake River Area Office.

Drought conditions have forced the closure of one electricity-generating unit at Palisades and are keeping the bureau on its toes trying to maintain the quality of water coming out of American Falls.

Beus said demand from irrigators, who own the water rights to what the dam holds back, likely will decrease following a hard freeze or rain. A hard freeze stops the growth of alfalfa hay but does not kill it.

Rain, obviously, would stand in for irrigation.

The high flows have left Jackson Hole anglers searching for options other than the Snake River through the valley.

Outfitters have sent trip after trip to the Salt River in Star Valley, putting unusual pressure on the small waterway. In the valley, guides are working hard to find even small fish during a month that is usually the tenderloin of the season.

Beus earlier this week met with a representative of the state engineer’s office and the state Game and Fish Department and park personnel.

“I had no good news to deliver,” he said. “We were hoping we could establish a ramping schedule.”

Rob Gipson, of Game and Fish, wrote in an e-mail that releases would remain at current levels through Sept. 28.

Following the irrigation season, the bureau decreases flows to a set winter regime, roughly between 300 and 500 cfs. With irrigation demand continuing, the bureau can make no plans until irrigators halt water orders.

It takes six days for water to flow between Jackson Lake and Milner, Idaho.

When the bureau is ready to ramp down releases, it will work with Game and Fish biologists to determine a schedule of cuts that balance the need to give fish time to move out of side channels and into the main river and holding as much water back as possible behind the dam, Beus said. This season, the ramp-down could be particularly steep.

On Thursday, Beus said he had a difficult time balancing the needs of river users with those of irrigators.

“We’ve had a tough summer and we didn’t want it to turn out this way,” Beus said.