The U.S. Bureau of Reclamation and U.S. Army Corps of Engineers on March 6 planned to increase Boise River flows through the city of Boise as part of flood risk-management operations.
Flows were slated to increase from about 280 cubic feet per second to 1,780 in daily 500-CFS increments March 6-8, Reclamation said in a news release. Heavy mountain snows in February prompted the move. During the Feb. 1-27 period, season-to-date snowpack rose from 74 percent of the long-term median to 124 percent while precipitation for February alone was 285 percent of normal.
A full supply of irrigation water is anticipated this summer, Reclamation said. Boise River reservoirs at month’s end were at 53 percent of capacity. Flood-control releases traditionally prompted some irrigators to worry they would not receive full allotments under their water right, but the Idaho Legislature this year passed House Bill 1 as a remedy.
“What a difference a month makes,” Nampa & Meridian Irrigation District Water Superintendent Greg Curtis said. “It looked like we would have a short supply a month ago. But now, with the releases they are planning for, it should ensure we have a full supply.”
The big increase in snowpack required district crews to make sure they completed any work on Boise River headgates before flood-control operations began, he said.
But every year, “we know in March we ought to have our stuff about ready to go,” Curtis said. In early March, work on check structures, pipelines, and miscellaneous concrete upgrades wraps up and ditch riders prepare routes.
Reclamation said additional flow increases are possible in coming weeks depending on weather conditions. Typical flood risk-management operations push Boise River flows up to 6,500 cubic feet per second through Boise.
The Corps of Engineers and the Bureau of Reclamation operate the three dams. The bureau’s Arrowrock and Anderson Ranch dams provide water-storage capacity. The Corps’ Lucky Peak Dam, through planned water releases, is used in managing river flows through the city.