Logan - I do not pretend to understand this situation. It is very complex. However I have gone to a couple meetings on the topic, and while most of it was confusing to me this is what I gathered:
Basically the water company bought water rights a million years ago for a donkey and a bushel of hay when Grand county had no concept of the number of golf courses and lawns they'd want to soak with our river, and now they own the water, period. The politicians (especially Senator Udall) are already on our side and fighting for us, but there is really nothing they can do to change the water rights. TU is trying to show the importance of NOT destroying this river/ecosystem and the unpopularity this will cause Denver Water if they do. While large corporations are ultimately about making money, they don't like to be hated either. This is where the petitions come it. Writing a letter is good too - make sure one goes to Denver Water though.
If I understood incorrectly, feel free to clarify.