Saturday, December 21, 2013

The channel connecting Black and Hawksnest ponds

Black Pond and Hawksnest Pond are very different.  Black Pond is shallow, filled with vegetation, and high in nutrients, while Hawksnest Pond is deep, mostly free of aquatic plants, and nutrient poor. 

Yet Black Pond is about a foot higher than Hawksnest. When water levels are high, a strong current flows from Black to Hawksnest.  This probably imports a lot of nutrients into Hawksnest.

In the 1950s tthrough the 1970s, the two ponds were connected only during very high water.  Even then, I did not notice much flow between them.  High bushes on the isthmus must have filtered any water that did flow from Black Pond.
Looking from Black to Hawksnest.  Grass in the water indicates strong flow.

Since then, a channel has been created between the two ponds.  In 2010, I found this channel and dammed it with rocks.  But the rocks were removed by someone within 24 hours!  This demonstrates that the channel was built, and is actively kept open.  It's most likely use is to allow boats to move from Hawksnest to Black Pond.

Black Pond needs to be included in Harwich's pond sampling program.  It's likely that sampling would find that Black Pond indeed has higher levels of dissolved phosphorus and other nutrients that could be a threat to Hawksnest.

Another concern is that if any invasive plants become established in Black Pond, they could quickly spread to Hawksnest.

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