We have had an unusually poor water quality this summer.  When our phosphorus readings are this poor it is necessary to draw down to dump this poor quality water out of the lake as soon as we can.  The late September draw downs are a recent phenomena due to improved water quality allowing us to enjoy the lake for a longer period.  When water quality is good the fall turnover moves higher phosphorus laden water to the upward which means we still capture some of the benefit of a draw down in the fall.

There is also the added change of our dam gate replacement installed a few years ago.  Before that our gate was hinged on the bottom allowing top waters to flow out which had phosphorus fed algae in the upper layers. This type of draw down was beneficial when our water consistently had algal blooms in the surface layers in late summer.  And catching the algal bloom before it died and dropped to the bottom of the lake necessitated an early September draw down.

Our lake water quality has improved over the years so that full algal blooms no longer consistently plague the lake.  Since we replaced the dam gate with a knife gate style design that opens from the bottom,  water flows from the bottom of the lake channel upstream of the gate.  Phosphorus readings typically are higher as you move down the water column, so we are still removing higher phosphorus contaminated water whenever we draw down.

The draw down will commence on September 10th and continue until the higher phosphorus contaminated water is replaced with consistently low phosphorus reading level water.  We are lucky to have a very large watershed from which to draw.  Sebasticook lake has a flushing rate of 1-1/2 times per year.  Actual draw down dates are determined each year by our Newport town water regulation committee based on that year’s water quality along with consideration for our lakeshore owners and guests use of the lake.

I hope this has answered your question.

Regards,

Deborah Ferrell

SLA Water Quality monitor (along with Jack Carson)