Sunday, March 03, 2024

Corps begins cutting back releases

| June 23, 2006 12:00 AM

Releases from Libby Dam are being decreased 1,000 cubic-feet per second every four hours until the total outflow is at 30,000 cfs, Libby Dam managers announced Tuesday.

Flows into Lake Koocanusa from Canada have slowed considerably during the past 48 hours with just over 17,000 cfs coming into the reservoir, down from more than 48,000 on June 17 and 43,700 cfs on Monday.

The River Forecast Center for the National Weather Service is expecting the flow into the reservoir to continue to recede.

The Libby reservoir elevation at 12 noon on June 21 was 2457.69 feet above sea level, which is 1.3 feet from full. Based on the latest forecast, outflows from Libby Dam will continue to be slowly decreased at a rate of 1,000 cfs every four hours until the total discharge is 30,000 cfs. The target outflow is expected to be reached on Saturday. It means only 6,000 cfs will be coming over the spillway at the dam.

Total discharge from Libby Dam at noon on Wednesday was 49,000 cfs down from 55,000 cfs on Monday.

In addition, the flows in local rivers and streams are dropping from weekend highs easing the flooding problems in the Bonners Ferry area. On Tuesday afternoon, the Kootenai River at Bonners Ferry remained nearly two feet above flood stage. It was expected to drop to flood stage by Thursday morning and below in the coming days. Corps emergency management teams are on the ground providing technical assistance at sites that have been affected. In Bonners Ferry, the Corps has assisted local emergency management officials with strengthening levees and providing assessments on weakened structures.

Last weekend, the Yaak River flows hit more than 4,000 cfs for the second time this spring. The first time came at the end of the unseasonally warm weather in mid- to late-May. By Wednesday, the Yaak River was dropping quickly and was flowing at 1,770 cfs.

Agricultural damage estimates in the north Idaho area are about $6 million according to Boundary County officials and there is damage to about 54 miles of dikes along the river with damage estimated at $1 million a mile.

On Monday, the U.S. Army Corps of Engineers was spilling 31,000 cfs down the spillway and running another 24,000 cfs through the turbines at the dam. The reduction in flows is coming as the spillway gates are slowly closed.

Montana Fish and Wildlife Service has already identified gas bubble trauma to downstream rainbow trout. The gas bubbles are caused by spill above 1700 cfs are the dam. Most of the trauma was one the bodies and fins of the trout.

The Corps began spilling water on June 8 to make room in the reservoir for runoff caused by large thunderstorms in the upper drainage. At first, the federal agency spilled 8,000 cfs with total outflows of about 32,000 cfs into the river. By June 9, the spill was increased to 14,000 cfs with total outflows from the dam of about 38,000 cfs. Last week, the forecast center was calling for inflows from Canada in the 59,000 to 60,000 cfs range. Last weekend, the spill was bumped to 31,000 cfs bringing total releases from the dam to 55,000.

The large increase in water caused the Corps to offer local property owners help with bank stabilization and sandbagging efforts.