(Since this 2014 report the Lake Management Committee reports very little fluctuation of the lake level - April 17, 2021)
Robin Harvey wrote a brief but very nice report on the history of the lake level, and you can see it HERE. The web site mentioned is HERE. Use it, for example, to see how much rain fell yesterday or this week, and how much the lake level rose as a result.
Core sampling, one at the beach and seven at the western side of the beach, showed nothing unusual and no flowing water. Robin Harvey later used a weighted-down plastic sheet on the lake bottom near the dock and found a possible leak where the plastic was sucked down. He will repeat the measurements during better weather, perhaps in the spring.