Your PUD
News Release
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Lake Chelan Basin Runoff Forecast
Chelan County PUD
News Release
4/4/2008
The April 1 Runoff Forecast for the Lake Chelan drainage basin is 107 percent of average for the April 1 to July 31 time period, expected to result in approximately 561,900 second-feet-day (SFD), or 1,114,250 Acre-Feet (A.F.), of water.
Moisture content in the soil (soil prime) appears to be average. Snow water equivalent at the below-listed sites is collectively 104 percent of average. Low-level snow in the Lake Chelan Basin appears to be above average. Snowpack densities range from 36-40 percent, which is average for this time of year.
Typically runoff begins in early April, however, runoff has not yet started this year. On April 1, 2008, the USGS Stehekin River gage reported a flow of 313 cfs, which is 50 percent of average. Current long-range forecasts are predicting 125 percent of average precipitation in April, average precipitation in May, and temperatures 2 degrees below average in April and May. Below-average temperatures in April and May may result in later-than-average runoff.
The elevation of Lake Chelan on April 1, 2008, was 1083.3 feet. There should be plenty of water for refill by July 1. The generation forecast for Lake Chelan is guardedly optimistic, as generation is expected to be intermittent until runoff begins. Spill will likely be needed late spring and early summer to manage lake elevations as the lake fills.
The Northwest River Forecast Center’s April 2008 Early Bird Forecast for the Columbia River at Grand Coulee is 97 percent of average runoff for the January-to-July period. At The Dalles, the forecast for January to July runoff is 95 percent of average. Forecasts for other local area basins range from below to above average. The Wenatchee River is forecast for 108 percent of average runoff April to September.
On the map is a color coded diagram of the Columbia River Basin, which shows Current Snow Water Equivalent in percent of average.
|
Snotel Site |
Elev |
Snow Depth |
Water |
Adjusted |
% of last yr Feb. 1 |
% of Avg |
|
Lyman Lake |
5,900' |
154" |
61.0" |
61.0" |
101% |
107% |
|
Park Creek Ridge |
4,600' |
124" |
49.8" |
49.8" |
100% |
120% |
|
Rainy Pass |
4,780' |
102" |
34.2" |
34.2" |
88% |
90% |
|
Miners Ridge |
6,000' |
144" |
52.3" |
52.3" |
98% |
100% |
| Stehekin Percipitation Nov.- March 24.4" |
60% |
97% | ||||
| Total April 1 – July 31 runoff forecast | 561,900 SFD 1,114,250 A.F. |
|
93% |
107% |