Lake Tashmoo

Lake Tashmoo is a 270-acre coastal pond on our north shore.

Fresh water enters the pond via groundwater and springs at its head. In the late 1800s those springs became the source for commercially bottled water and for the Town’s first public water supply system. A meandering inlet connected the lake to Vineyard Sound and was an actively fished herring run. After the Great Gale of 1938, the U.S. Army Corps of Engineers dredged the inlet and constructed jetties that created the current estuary and stabilized the opening for navigation.

Lake Tashmoo is an important recreational resource: a safe refuge for boaters and a haven for beach-goers, kayakers, and fishermen. The lake also supports important shellfish resources and diverse fish populations. TWI assisted in funding the construction of a herring run at the head in the hopes that herring, which are an important food source for both commercial offshore fish species and near shore recreational fish species such as bluefish and striped bass, will return in greater numbers.

In recent years, water quality has deteriorated due largely to increased population growth (and accompanying Title V septic systems) in the watershed. Reduction in the size of extensive beds of eelgrass is considered a sign of poorer water quality. The report from a 2021 eelgrass survey of part of Tashmoo was published early Spring 2022.

It has been proved that reduction of nitrogen loading is key to improving water quality. In the 1990s TWI initiated an extensive project installing first flush basins and catch basins on roadways contributing polluted road run-off to the lake. It has contributed funding to the Town’s pump-out program and funded an assistant harbormaster position to assist with public education. TWI has also been influential in promoting dredging efforts which improve circulation and water quality.