Boise River managers came up with a game plan this irrigation season that allowed them to maintain the water supply even while the level of Lucky Peak Reservoir was lowered so a boat ramp could be repaired.

The Lucky Peak drawdown prompted some concern that irrigation water would not be available at the end of the season, said Ryan Hedrick, a hydrologist with the U.S. Bureau of Reclamation Middle Snake Field Office water operations team.

But because managers used another reservoir in the system differently this year, late-season supply will not drop, he said.

“Irrigation demand will still be met until the first or second week of October,” in line with long-term average shutoff timetables, Hedrick said.

The Boise River’s three main reservoirs are Anderson Ranch, Arrowrock and Lucky Peak. Reclamation owns Anderson Ranch, the biggest and farthest upstream, and Arrowrock. The U.S. Army Corps of Engineers owns Lucky Peak, the farthest downstream and closest to Boise.

Managers from June through August usually release Arrowrock water to meet irrigation demand.

This year, “we were using Lucky Peak water, particularly in July and August,” Hedrick said. Drafting or releasing water from Lucky Peak met irrigation demand and made room for the boat ramp project.

Managers in turn kept Arrowrock outflows lower than inflows to store water for late-season irrigation. Additional volume saved in Arrowrock offset the outflow from Lucky Peak.

Higher Lucky Peak outflow “wasn’t wasted,” Hedrick said. “It was still used to meet demand and flow-augmentation requirements.” Annual flow augmentation aims to benefit migrating salmon and steelhead.

At Anderson Ranch, managers reduced outflows recently.

“Our goal is always to use storage out of Arrowrock and Lucky Peak, and leave as much water as we can up in Anderson,” Hedrick said.

At Lucky Peak, the Turner Gulch boat ramp improvement project is slated from early September to early November, when reservoir refill will begin, according to the Corps of Engineers. A phased drawdown was started in late July.

Lucky Peak was at 2,930 feet Sept. 5 compared to an average of 3,023 for this time of year, Hedrick said.