Your PUD News Release

Early forecast puts 2011 Lake Chelan runoff at 82 percent of average

Chelan County PUD
News Release
2/4/2011

The forecast for 82 percent of average runoff would result in an estimated 430,582 second-feet-day (sfd) or 864,844 acre-feet (af) of water. Last year’s actual runoff from April 1 through July 31 was 531,049 sfd, which was 101 percent of average.

Snowpack densities at the above listed sites range from 34-38 percent, while average at this time of year is 34 percent. Precipitation in Stehekin from October through January was 24.5”, which is 112 percent of average and 109 percent of last year’s accumulation at this time. Moisture content in the soil, also known as soil prime, is near average.     

The Northwest River Forecast Center’s Jan. 27 early bird runoff forecast for January through July is 98 percent of average at Grand Coulee Dam and 101 percent of average at The Dalles, while the early bird forecast for April through September is 86 percent of average for the Wenatchee River and 88 percent of average for the Okanogan River.

One notable weather forecaster is predicting relatively warm conditions on the West Coast until late February, when conditions are expected to shift back toward a typical La Nina pattern. Colder temperatures and above-average precipitation are then expected to prevail, bringing more snow across the interior Northwest, and mostly rain west of the Cascades.

The elevation of Lake Chelan on Feb. 1, 2011, was 1088.01 feet, which is 0.9 feet higher than the expected average under the current operating license and 3.6 feet lower than last year. This year the elevation of Lake Chelan is slightly higher than the expected average because of significant inflow into Lake Chelan during mid-January 2011.

Generation will be managed this winter and spring with the intent of meeting operating objectives in the Lake Chelan Hydro Operating License as well as minimum lake elevation targets.

At right is a color coded diagram of the Western United States and the Columbia River Basin in Canada, which shows mountain snowpack in percent of average snow water equivalent. Note that snowpack in North Central Washington basins range mostly from 50 percent to 89 percent of average.