Dark Bottom Pond

Brewster’s ponds provide important habitat for aquatic life and are a great natural resource for our community. Yet, the scenic beauty and recreational benefits we enjoy from them masks growing problems beneath the surface.

Many of our ponds suffer degraded water quality from both historic and current activities. Many are reaching their tipping points, where further alterations to the environment will result in sometimes dramatic changes. These have included recent noxious and potentially harmful cyanobacteria blooms in Cliff, Elbow, Seymour, Smith, Walkers Ponds, and Long Pond.

Only five of Brewster's Ponds are now considered to be of high quality when compared to Cape Cod Commission pond guidelines, Mass DEP water quality standards and other general indicators of pond health. A vast majority of Brewster's ponds suffer some level of impairment including lack of clarity (high chlorophyll,) nutrient loading (high phosphorus) and low dissolved oxygen, which limits survival in the aquatic habitat. (Click on map above to see your pond's status.)

Cape Cod's Ponds serve as a looking glass into the future of our drinking water. Cape Cod's sole source aquifer provides 100% of our drinking water.

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Image of cross section of Cape Cod's groundwater aquifer. Courtesy of USGS

The groundwater is recharged entirely by precipitation and is extremely susceptible to contamination from various land uses and activities. Cape Cod's drinking water quality is generally very good. But, over the past fifteen years, there has been a trend toward some degradation. Nitrate levels in public drinking water supplies are rising. The correlation between human development and aquifer degradation is evident.  Cape Cod Aquifer link here.

According to the 2009 Brewster Freshwater Ponds Final Report, a review of total nitrogen to total phosphorus ratios shows that all Brewster ponds are “phosphorus limited,” which means that management of phosphorus will be THE KEY for determining water quality in these ponds. It also means that reductions in phosphorus will have to be a part of any remediation plans.

Because phosphorus moves very slowly in Cape Cod's aquifer, it can take decades for some loads from even near-shore sources, such as septic systems, to reach a pond shoreline and discharge into a pond. This study goes on to say that only a fraction of the nutrients now in the aquifer have reached the ponds, and that water quality will worsen.