March a nice

March a nice, wet month in the basin

April 7, 2014

Libby Dam's April water supply forecast for April to August has been helped considerably by a lot of moisture received in the region in March, an extremely wet month in the Kootenai Basin.

This led to the large increase in forecast from the Army Corps of Engineers' March forecast.

Many places in the basin received 200- to 300-percent of normal rainfall. The snowpack grew by 150-percent of normal in many places, and current weather in the area will likely lead to snowpack continuing to grow in the next week or more.

The forecast is for 6,868 thousand acre feet (KAF), 117-percent of average. This sets the April 30 flood control target at 2,377.2 feet. The current elevation of Lake Koocanusa is 2,413.8 feet.

Libby Dam has been at full powerhouse capacity, discharge of ~26,000 cubic feet per second since Monday, March 31. Releases from Libby Dam will remain at full powerhouse capacity for the month of April or the start of refill, which ever happens first.

The current median projection for the end of month elevation is ~2,387 feet. The actual lowest elevation reached this year could vary +/-10 feet from ~2,387 feet, depending on actual inflow in April.

There are no plans to spill during the month of April.

To see the Corps' April runoff forecast and flood control calculation, click here.

The May water supply forecast should be issued by May 7, which will set the sturgeon volume and bull trout minimum flow.