19-042 Boise River flows to increase on Tuesday

Published April 29, 2019

 The U.S. Army Corps of Engineers will increase flows through the City of Boise by 200 cubic feet per second (cfs) on Tuesday, April 30. Currently, Boise River flows through town are approximately 6,420 cfs, as measured at the Glenwood Bridge gauge. Flows will reach approximately 6,620 cfs by mid-morning on Tuesday.

The increase in flows from Lucky Peak Dam and Lake is in response to above average precipitation the Boise River System has received so far in April. As of April 28, the Boise River basin has received 147% of normal month-to-date precipitation, and the snowpack in the basin is 116% of normal according to the Natural Resources Conservation Service. These 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 also 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. As the river nears that level, 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. 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.

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 at https://www.weather.gov/boi/. The site offers flow data, weather forecasts, and flood alerts. Follow flood-response instructions issued by your local emergency management agency https://adacounty.id.gov/emergencymanagement/, and tune-in to local radio and television news stations. Ada County residents can sign up for CodeRED emergency alerts at https://public.coderedweb.com/CNE/en-US/BF01DC4DD213, or download the CodeRED mobile app from your mobile device’s app store.

Currently, the Boise River reservoirs are at 83% of capacity. 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, visit https://www.usbr.gov/pn/hydromet/rtindex/boise.html.

Public Affairs Office

Release no. 19-042