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My name is Julie Wood, and I am a senior scientist at the Charles River Watershed Association
headquartered in Weston, MA. Although our office is in Weston, MA, the association's
area of concern and focus is the entire 308 square-miles of the Charles River Watershed.
Within this 308 square-mile watershed, we encompass 35 Massachusetts cities and towns.
One aspect that we focus on at the watershed is the impact that dams create along the
river. The Charles River is 80 miles long, and there are 20 dams long this 80-mile stretch.
Because of this high density of dams, most sections of the Charles are impacted by one
dam, some way or another. The systems of dams have a major impact on the river and the watershed.
Some of the dams create significant backwater environments. One of these dams is the Moody
St. Dam in Waltham, MA. Behind the Moody St. Dam, the river widens, slows down and creates
an area that we call the 'Lakes District'. The Lakes District is an area where the Charles
is much wider than other areas. There are small coves and inlets. This area generally
stretches from the Moody St. Dam upstream to Commonwealth Ave. in Newton. This area
is bordered by the towns of Waltham, Newton and a small piece of Weston. In the Lakes
District, we have a major issue with invasive water chestnuts. And we are starting to have
emerging issues with other nuisance vegetation. As I mentioned, this area is slow moving,
wide, shallow water area. We also have in the Lakes District -- as we do in all areas
of the Charles -- a major issue with phosphorous pollution. Phosphorous -- which is typically
the limiting nutrient in a freshwater system (meaning that once it runs out you would not
get any more plant growth) -- is extremely abundant in the Charles. We have about twice
as much phosphorous entering our river than would be found otherwise in a natural, unimpacted
system. This phosphorous gets into the river and essentially fertilizes the river. So it
allows these plants, such as invasive water chestnut, to grow prolifically, unchecked,
more so than they would in a natural unimpacted environment. In the Lakes District, the water
is also shallow, heats up quickly and promotes overgrowth of this kind of aquatic plant.
The issues that these invasive plants cause can be varied. In the case of water chestnuts,
they're allowed to grow because of the phosphorus. Additionally, because they are invasive -- meaning
non-native to this region -- they do not have many predators or native limiting factors.
They grow in very dense mats on the surface of the water. One issue it causes for humans
is they make it very difficult to canoe through this region. The Charles River Lakes District
has historically been used very heavily for recreation. It is a really nice place to take
a paddle. It also has a lot of environmental and ecological impacts as well. The fact that
they sit on the water -- on the surface of the water -- makes it difficult for sunlight
to penetrate down into the water to provide sunlight to submerged aquatic vegetation.
Additionally, it limits oxygen exchange across the surface of the water. When this large
mass of plants dies, in the fall and winter months, it sinks down to the bottom, and,
as it degrades, it uses up dissolved oxygen in the water column. This dissolved oxygen
is what fish and other aquatic animals actually use to breathe. So, it can actually cause
fish -- in severe cases -- to potentially suffocate and form what is known as a 'dead
zone'. Invasive species can cause a variety of different issues in different environments
and the water chestnut is not the only invasive [species] threatening the Charles River. The
issues that dams cause can also be numerous. In addition to slowing down and heating up
water, -- impacting the natural flow of a river -- they also impact the natural movement
of aquatic life, such as fish and other animals. In the Charles we have some species of what
we call 'anadromous' fish. Those are fish that live most of their lives in the ocean
but come into the river to spawn or lay their eggs. These fish need to make the voyage from
Boston Harbor up through the Charles into a nice, secluded, protective area where their
eggs will be protected and able to grow. In the Charles, since there are so many dams,
this voyage can be difficult for fish. Additionally, the native species that live here often cannot
travel as far as they would naturally because they are bound by dams. Many of the dams in
the Charles do have 'fish ladders' or some type of fish passage. But depending on
the type of species, not all fish ladders work very well. And, of course, it is a much
different way of travel than the fish would naturally expect in a natural environment.
So there are ways to improve fish passage on existing dams, but, of course, dam removal
is the ultimate goal for river restoration.