"Corporations, and the government for that matter, are made up of people."
And I'd emphasize, made of people who can have responsibilities. We can regulate a corporation, and the result is real people have to do real work or make real changes somewhere, or the regulation is meaningless. Treating a corporation like a big person makes sense in at least some ways.
You may legislate all you like, but the river is not going to fill out an environmental impact statement in advance of its next flood. It's not a person. It can't have responsibilities.
A river is made up of those who live along it, a farmer that dumps manure into it is effecting it - similarly the community downstream has certain rights when it comes to their waterway, they may be farmers that purchased access to the waterway with their lands, or residents that purchased their property with an expectation of being able to swim or even a home owner who is pursuing damages against the flood of a river where an insurance company needs to determine if an upstream private party was responsible or the river itself.
Basically, I agree with your statement that a river doesn't have personal rights or responsibilities but those people effected by mal-treatment of the river (including, if no one else advocates, a state/local government) should have the right to protect against unrestricted mistreatment.
Nothing that isn't a natural person should be treated like a person, everything outside of an individual should have separately delineated rights afforded to it depending on the type of object it is. We can sanely fix this problem (and citizen's united) by just agreeing to shift some definitions.
And I'd emphasize, made of people who can have responsibilities. We can regulate a corporation, and the result is real people have to do real work or make real changes somewhere, or the regulation is meaningless. Treating a corporation like a big person makes sense in at least some ways.
You may legislate all you like, but the river is not going to fill out an environmental impact statement in advance of its next flood. It's not a person. It can't have responsibilities.