Lake Committee Chair
On the 15th of October, we opened what we lovingly call the anaerobic valve located in our release tower by the dam. This is a six-inch valve located 40 feet beneath the surface and in the oxygen-depleted (anaerobic) water below the thermocline (barrier between the oxygenated water above and the anaerobic water below).
This stratification of the lake takes place in the spring and lasts into late October or early November, when the water mixes again and the oxygen levels equalize at all depths.
We open this valve for several reasons. It releases oxygen-depleted, high-nutrient water and is healthy for the lake. This water then re-oxygenates and remixes as it flows down Deer Creek. It also produces a colder, steadier flow to the confluence of Deer Creek and the Yuba River, a spawning ground for salmon.
This has been requested by our friends at Sierra Streams Institute. In addition, it satisfies our immediate obligation under our water rights (that begin Oct. 15) to provide a flow equal to what is entering the lake or 5 cfm (cubic feet per minute), whichever is less.
Even when NID closes its irrigation season, we always get some flow into the lake after that date and for sure if we get precipitation.
We can always adjust our valve, depending on the inflow from Deer Creek, if we need to minimize the lake level drop that will probably occur.
Bottom line, we don’t know for sure how much the lake will drop since there are multiple variables involved. If there were no flow into the lake and no evaporation, the open valve alone would cause a drop of about a third of an inch a day.
That may affect the utility of some hydraulic boat lifts for a short period of time but should not have a material effect on the boat launch ramp in Meadow Park.
The decision this year whether to lower the lake was a tough call. With the potential for heavier than usual El Nino precipitation on the horizon, the odds for a wet winter increase significantly, but there is no guarantee.
The California Water Control Board has a curtailment in place again for the Sacramento River watershed and we cannot retain water until it is lifted.
Even though we believe it will be lifted at the first significant precipitation, there is no guarantee. There is also no guarantee of additional rain from this El Nino, for that matter, especially this far north. Every meteorological prognostication I have read or seen makes that disclaimer.
In the event of a significant or inordinate amount of rainfall, we will likely take a fair amount of silt accumulation in Deer Creek and could face the need for silt removal again next fall.
Better to only lower the lake once than face the prospect two years in a row. Sooooo, enjoy the lake and boating for another full season.
The next Lake Committee meeting will be Wednesday, Oct. 28, in the Marina Room. Tom McNabb of Clean Lakes (our herbicide vendor) will be the guest of honor and will review our 2015 herbicide program and present a proposal for 2016. Committee meetings are always open to members, but this may be of special interest to lake lovers.
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