I was more like a fish than a child.
Sounds pretty awkward. I think removing this bit would be a good idea.
spent used to spend hours pretending I was a mermaid in Pinckney's Chain of Lakes.
This sounds better... to me.
s werewas my favorite time of the year
my parents took my sisters and
I love the smell of the water, I love ice skating on winter's frozen lakes, I love the snapping turtles perched on the fallen trees, I love canoeing from Dexter to Ann Arbor
If you insist on using the repetition, then you should use semi-colons or periods instead of commas.
the Huron River Watershed has been and
always will always be a significant part of my life.
I want it to be enjoyed
,and protected by , and thrive for many generations to come.
I don't think it's the best way to fix the problem. But the preposition "for" doesn't work for either enjoyed or protected here.
Aside from its unique beauty and abundant space for leisure, the Huron River Watershed supplies drinking water for about 150,000 people.
Moving this sentence to right before the previous sentence seems more logical.
Unfortunately, the Huron River, like much of Earth's water systems, is
being threatened by development, soil erosion, dams, impaired water bodies, and non-point source pollution.
"Nonpoint source pollution" is spelled without the "-". Also, what kind of development are you referring to? You mentioned dams, which could be thought of as a part of that development.
This is a lot to take on for a fragile eco-system.
I'm not too sure if by "a fragile eco-system" you were referring to the river. Again, discard the "-", as ecosystem is spelled without it. Plus, "this" should be replaced by "there", "to take" by "to be taken"... I suggest you just remove this sentence altogether.
The ideas in the second & third paragraphs are jumbled up. The best way to revise them would be to concentrate on describing the harmful effects of the pollutions in the second, and talk about the ways people could contribute to reduce the pollutions in the third.
The last paragraph is just a repetition of things you mentioned previoiusly, and thus, unnecessary. Focus more on answering the question: "How do you think it should be addressed?"
If I were you, I would briefly talk about how the government and the firms could also help to reduce pollution and add something like, "HOWEVER, the most solution to this problem is awareness..." and so on, though this sort of response sounds very, very hackneyed...:/
Hope this helps.