Your PUD News Release

Early forecast puts 2010 Lake Chelan runoff at 83 percent of average

Chelan County PUD
News Release
2/8/2010

The Feb. 1, 2010, runoff forecast for the Lake Chelan drainage basin is 83 percent of average for April 1 through July 31.  The 83-percent-of-average runoff would result in 435,800 second-feet-day (SFD) or 864,190 Acre-Feet (AF) of water.  Last year’s actual runoff from April 1 through July 31 was 427,051 SFD, which was 81 percent of average.  Current long range weather forecasts are calling for a drier and cooler than average February, and a slightly wetter and warmer than average March.               

Snowpack densities at the above listed sites range from 30-36 percent, while average at this time of year is 34 percent.  Precipitation in Stehekin from October through January was 22.4”, which was 105 percent of average and 103 percent of last year’s accumulation at this time.  Moisture content in the soil, also known as soil prime, is average.     

The elevation of Lake Chelan on Feb. 1, 2010 was 1091.60 feet above sea level, which is 4.5 feet higher than the expected average under the current operating license, and 2.0 feet higher than last year.  The elevation of Lake Chelan is significantly higher than the expected average because of:

• Decreased powerhouse capacity due to modernization of both generating units.
• Significant rainfall in November 2009. 

Generation will be managed this winter and spring with the intent of meeting all seven operating objectives in the Lake Chelan Hydro Operating License, as well as minimum lake elevation targets.  The first minimum lake elevation target in 2010 is 1087.6 feet on May 1.  Generation will likely be scheduled at maximum available capacity (which is less than average due to modernization efforts) through this winter and spring, unless future runoff forecast drops below approximately 80 percent of average. 

The Northwest River Forecast Center’s (NWRFC) official runoff forecast (regression method), for January through July, is 81 percent of average at Grand Coulee Dam and 74 percent of average at The Dalles.  Runoff forecasts for other local area basins are also below average.  The NWRFC’s runoff forecast, for April through September, is 75 percnt of average for the Wenatchee River and 74 percent of average for the Okanogan River. 

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 Central Washington basins range mostly from 70 percent to 89 percent of average.