Today, Friday, March 3, the Lake Chelan Lake level is 1,085.7 feet – “well within the PUD’s Oct. 1 Forecasted Operating Range,” says Senior Analyst, Becky Keating. “We model the operating range using historical inflows combined with current operating constraints. These models give us target curves to help guide us with things such as generating power at the dam or spilling water. All of this is part of our operating license for the dam from the Federal Energy Regulator Commission (FERC) to help us meet a variety of operating objectives including recreation, fish habitat, dam operations, and erosion control.”
Keating explains that what we are seeing this year is much more typical of a dry to normal water year in the Chelan Basin for inflows and lake levels. In fact, although it seems like there is much more snowpack in the valley this year, that’s really not the case in the mountains surrounding the lake, where snow levels are running about 90 percent of normal at this point. Why the lake looks “low” this year, she explains, is due to the past two years of very, very high inflow into the lake earlier than usual. “The heavy rains we received at the end of 2014 and 2015 and prolonged high inflows received during both winters, meant that the lake was higher than what it usually is in the late winter and early spring of both 2015 and 2016.”
Uncertain inflows and weather are the greatest challenges for lake level management. By using the target curves, the PUD expects to be able to manage the level of the lake to meet operating objectives 90 percent of the time. 2016 is a good example of the uncertainties Mother Nature hands lake level planners. Unlike 2015, where lake levels were kept higher because of the 64 percent of average snowpack and the concern for mid-summer lake levels, 2016 had a great snowpack at 116 percent of average. Yet, an exceptionally warm April meant snowmelt came very early – along with record inflows that already had occurred earlier in the season. Because the lake was already higher than usual and a scheduled spring generating unit outage for maintenance limited generation, on May 1, 2016, the lake was EIGHT feet higher than expected.
Climate change? We can’t say that right how. Chelan PUD is watching the regional studies that are underway to get a better idea of what’s happening.
So, no, the Lake Chelan lake level isn’t low for this time of year. Really.
We have a more detailed explanation on our blog.