Pond Height & Spring Opening:
Edgartown Great Pond is connected to the Atlantic Ocean 3-4 times per year when a manual breach is made in the barrier beach that separates the Pond from the sea. This breach or “cut” is made when the height of the Pond is approximately 3-4 feet above sea level. Pond height, wind, tide, and moon cycles all come into play when choosing the best time to make the cut.
The opening[s] are scheduled by the Shellfish Committee for March 15, May 15, August 15 & Nov 15. [T]he schedule has not changed but is obviously a schedule that depends on various factors beyond my control.Paul Bagnall, Edgartown Shellfish Constable
When the cut is made, the Pond drains for about a day and then a tidal flush of the estuary begins when cool, clean, salty, and oxygenated water enters the Pond with the tides. This flushing of the estuary has been an effective management tool employed over the last decade to reduce the nutrient accumulation in the Pond and maintain the salinity at levels sufficient to support the eelgrass and oyster populations.
In mid-November of 2018 the Pond reached a height of about 3.6 feet above sea level. After a successful cut, the Pond drained for 24 hours, and then experienced a tidal flush for 3 days. For several weeks afterwards the Pond height changed dramatically from day to day as the cut came open and closed and the Pond became intermittently tidal. By mid-late December the Pond closed firmly and the recharge period began. The water level in Edgartown Great Pond increases through both precipitation and groundwater recharge.
Edgartown Great Pond is currently 1-2 inches above the height it was when it was last cut on November 18th, 2018. Paul Bagnall anticipates the next cut will be around March 15th. For context, Edgartown Great Pond is currently about 1.5 feet lower than it was at its peak height in March of 2018.