21 May 2016: Clary Lake Dam’s Gate Almost But Not Quite Closed

IMG_20160521_094122 (Custom)Late last Thursday afternoon for reasons known only to himself, the Clary Lake dam owner closed the dam’s gate to within about 7″ of completely shut. As you can see from the picture at left, there’s still quite a bit of water flowing out of the lake but the mill pond behind the dam has considerably more water in it than when the gate was wide open. However, while the water may be backing up behind the dam, the lake level is still falling about 1/4″ per day. Remember, water only flows down hill and there is a mile and a half of meandering channel down which the water has to flow to get from the lake to the dam. With the gate wide open and the lake this low, I suspect the water level right at the dam itself has been as much as 2 feet lower than out on the lake, perhaps even more. I’ve actually measured a 3″ difference when gate was wide open and the lake was almost full. Albert Boynton whose family owned the dam in the 1920’s and who was actually born in the little red house on the dam told me once that after a morning of sawing lumber, the upper mill pond would have fallen considerably; when they returned from dinner, it would be full again.

Coming as it does so close to the June 1st deadline when Mr. Kelley is expected to submit a plan to DEP to fix the dam and restore the lake level, one wonders if there is a reason he has decided to close the gate at this time. Perhaps so. In any case, no doubt Mr. Kelley has left the gate open a small amount to comply with the requirement in the Water Level Order (WLO) that the dam operator maintain Minimum Outlet Flows to sustain the downstream aquatic habitat. To help the dam operator maintain these minimum flows, DEP calculated approximate gate openings necessary to let out the required volume of water, and included them in the WLO:

  • 11.3 cfs (0.7 feet of opening above the invert of the outlet) between January 1 and March 15;
  • 35.9 (or 1.6 feet of opening above the invert of the outlet) between March 16 and May 15;
  • 8.3 cfs (0.6 feet of opening above the invert of the outlet) between May 16 and June 30;
  • 1.9 cfs (or 0.2 feet of opening above the invert of the outlet) between July 1 and September 15;
  • 3.5 cfs (or 0.3 feet of opening above the invert of the outlet) between September 16 and November 15; and
  • 15.5 cfs (0.9 feet of opening above the invert of the outlet) between November 16 and December 31.

As you can see, for the period between May 16 and June 30 the gate should be open 0.6′ (7.2″) to allow 8.3 cubic feet of water per second to be released down stream, and that is in fact about how open the gate is.

In reality, the WLO requirement is that the dam operator release the Minimum Flows for the time of year or actual In Flows WHICHEVER IS LESS. Therefore, it is anybody’s guess as to whether the right amount of water is actually being released. My guess is, given how dry it has been lately, that too much water is being released. We’ll see in a few days if the lake keeps dropping.

Please review our “Minimum Flows Explained” page for more information about this important and confusing topic.

 

1 thought on “21 May 2016: Clary Lake Dam’s Gate Almost But Not Quite Closed

  1. George Fergusson Post author

    The lake fell 0.01′ (0.12″) since yesterday morning indicating the rate of fall has been cut in half since the gate was closed. We’ll see if the trend continues,

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