Why did the lake level drop 5 inches in seven days?

Please take a look at the lake level / dam spillway log for August on the right, you will notice that once the spillway level receded to 0" and water stopped spilling over the dam the lake level held steady at between -5.5" and -6.5" below normal depth for 10 days. It is my belief that at this point the only natural variable that would cause the lake level to go down would be evaporation. Beginning Aug 13th lake level began to decline at the rate of 1" a day with all gates closed. This is obviously way to fast for evaporation, and should be setting off flags that there may be issues with the integrity of the dam and/or dam gates. I don't recall the lake level ever declining at such a rate with the gates closed.

From the Twp of Hamilton website "Attention Waterfront Residents 7/27/07 - Please be aware that the water level of the lake is slowly going down. This is occurring on its own and is not an act from the County or the Township. We believe that the water is going down due to the lack of rain and high temperatures from the summer heat. All three gates are closed and there are no plans in the immediate future to open them."