​There are actually two valves on the dam, a new one and an old one. The new one was added in the early 2000s and is inside the 18½-inch diameter pipe that passes through the dam. The old one, which came with the original dam, is at the entrance to the pipe. The two valves are in series so that either one is all that is needed to control or stop the flow of water through the dam. That is the only thing that they actually do. Closing them creates an opportunity for precipitation or runoff to raise the lake, but does not necessarily raise the lake.  They are often called “drain valves” as opening them partly drains the lake.

During the cold weather, the new valve is locked open so that it will not freeze, which would severely damage it. It's not something we can repair, which means that it would have to be removed from its concrete encasement and sent back to its manufacturer for any repairs.

Little Known Fact: It takes 190 turns of its operating wheel to fully open or close the new valve. That's great exercise, but tedious, time consuming and if you don't keep count, you just don't know how open or closed the valve might be.

On the other hand, the old valve is not damaged by freezing, can be repaired locally by any carpenter, is easy to operate and how much it is open/closed is easy to determine visually. Unfortunately, it leaks a bit. Therefore we use the old valve mostly to control the rate of out-flow when down drawing the lake, and use the new valve to totally shut off out-flow in the warmer weather (keeping the lake level as high as possible).

From this point on, the two serial valves will be referred to simply as “the valve”.

The valve is used to change the lake level from its normal maximum value (i.e. full for the summer with water flowing out through the spillway), to its normal minimum value, (i.e. down drawn for the winter with water only flowing through the regulated valve). Both normal levels are only semi-stable, as fluctuating weather conditions can cause large changes to the amount of water going into and/or out of the lake at any given time. In the summer, the most significant change is caused by normal evaporation (about 1-inch of lake level is lost to evaporation each week in the summer), and that water loss which is exacerbated during times of drought. In the winter, the large changes are driven by rain falling on our frozen watershed, with little loss due to evaporation, causing the lake to rapidly rise. In simple terms, the lake has two normal semi-stable levels. Summer approximately full and winter, down drawn; depending on whether or not the valve is open or closed.

We usually open the valve just after Columbus Day to start to down draw the lake. With the valve fully open, it usually takes about a month or so for the lake to go down to its normal minimum level.

Everyone needs to fully understand that closing the valve at the end of the winter does not raise the lake level. Nearly all of the time, the lake level is going down due to evaporation notwithstanding how much the valve may be open or closed. Only rain and/or a melting/thawing watershed can raise the lake level.