
In Illinois, we are a largely agricultural state, so the pesticides and chemicals from farming impacts our state's watershed. Supporting local and organic farmers or growing your own garden could help with this.
In the suburbs of Chicago where I live, I think some of the biggest human activities impacting our water is improper lawn care (using too many pesticides on our lawns to keep them green) and that there is so much pavement, which makes it harder for water to naturally infiltrate back into the ground and also picks up pollutants from vehicles on it's way into the sewers and ground. Weeding by hand, while time consuming or looking into natural lawn care options are other alternatives to all of the chemicals. When possible removing turf grass and replacing with native plants.