BOISE, Ida. — The U.S. Army Corps of Engineers will increase Boise River flows through the City of Boise on Thursday. The flows are expected to increase 200 cubic feet per second (cfs).
Currently, the Boise River flows through the city are approximately 6,620 cfs, as measured at the Glenwood Bridge gauge. Flows will reach 6,820 cfs later this morning. The increase is from Lucky Peak Dam and Lake in response to a coordinated run-off forecast of about 1 million acre-feet of anticipated inflows to the Boise River system during May through July.
As of May 1st, the Boise River basin has received 112 percent of normal October-to-date precipitation, and the snowpack in the Basin is 115 percent of normal according to the Natural Resources Conservation Service. The increases from Lucky Peak Dam and Lake are necessary to help reduce the risk of flooding later in the spring, which can happen with rapidly melting snow and seasonal precipitation.
Additional adjustments in water releases from Lucky Peak Dam and Lake are likely during the coming days, depending on weather conditions and resulting inflows. Flows could fluctuate depending on water diversions for irrigation use, as determined by Idaho Water District 63. Any increase in irrigation demand will prompt an increase in water releases from Lucky Peak to maintain the target rate of flow at the Glenwood Bridge gauge.
A flow rate of 6,500 cfs, or about 9.6 feet in depth, at the Glenwood Bridge gauge is considered bankfull. A flow rate of 7,000 cfs, or about 10 feet in water depth, at the Glenwood Bridge gauge, is considered flood-stage level on the Boise River. Large sections of the Greenbelt path adjacent to the river will likely become submerged, and minor flooding may affect portions of Eagle Island. The Greenbelt serves as a flowage easement area, intentionally designed to provide space for higher flows occurring in the Boise River.
Officials advise the public to be aware of risks associated with flood season. The water is deep, cold and fast. Extreme caution should be used near the river banks.
Residents of flood-prone areas in and near the greater Boise area are encouraged to keep informed of changing river, stream, and weather conditions on the National Weather Service Boise Office website. The site offers flow data, weather forecasts, and flood alerts. Follow flood response instructions issued by your local emergency management agency, and tune-in to local radio and television news stations. Ada County residents can sign up for CodeRED emergency alerts here, or download the CodeRED mobile app from your mobile device’s app store.
Currently, the Boise River reservoirs are at 83% of capacity. As of May 1, the Boise River system of reservoirs has 159,647 acre-feet of available storage space. A full supply of irrigation water is anticipated this summer.
The Corps of Engineers and the Bureau of Reclamation operate three dams on the Boise River as a system to manage flood control and irrigation storage needs--Lucky Peak Dam, Arrowrock Dam and Anderson Ranch Dam. Storage capacity provided by Reclamation’s Arrowrock and Anderson Ranch dams, and the Corps’ Lucky Peak Dam, combined with well-planned water releases, help manage Boise River flows through the City of Boise. For real-time Boise River flows at Reclamation facilities in the Pacific Northwest Region, click here.