Your PUD News Release

Final Lake Chelan runoff estimate is still far below average

Chelan County PUD
News Release
4/1/2010

The April 1 runoff forecast for the Lake Chelan drainage basin is 83 percent of average for April 1 through July 31, 2010.

Eighty-three percent of average runoff would result in 435,800 second-feet-day (SFD) or 864,250 acre-feet (AF) of water. Last year’s actual runoff from April 1 through July 31 was 427,000 SFD, which was 81 percent of average. Long-range weather forecasts are calling for a slightly warmer and wetter than average April, and a slightly wetter than average May.               

Snowpack densities at the sites listed below are approximately 3 percent lower than long-term averages. Moisture content in the soil, also known as soil prime, is average.     

The elevation of Lake Chelan on April 1, 2010, was 1090.0 feet above sea level, which is 4.6 feet higher than the expected average under the current operating license, and 3.9 feet higher than last year at this time. The elevation of Lake Chelan is significantly higher than the expected average, mainly because of decreased powerhouse capacity due to modernization of powerhouse generating units.

Generation will be managed this 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 the spring.

The Northwest River Forecast Center’s (NWRFC) official regression runoff forecast for January through July is 74 percent  of average at Grand Coulee Dam and 65 percent of average at The Dalles. Runoff forecasts for other local area basins are also well below average. The NWRFC’s runoff forecast, for April through September is 67 percent of average for the Wenatchee River and 65 percent of average for the Okanogan River.

At right is a color-coded diagram of the western United States, which shows mountain snowpack in percent of average snow water equivalent. Note that snowpack in the central Cascades and Central Washington basins are all below average.