Your best bet would be to contact the local agency that controls the area. They may refer to a ditch company or someone else that manages the water shares.
Might be a longshot but do a google search on the lake you are interested in. Weed through the 1,567,986 "web-hits" until you find some PDF files listing the controlling agencies in some open hearing. (You may have to do a second search on the name of the ditch company itself)
The Church Ditch company controls some water in Westminster area and they help me out now and then with all kinds of questions.
Tip: Be very polite and to the point with your questions. Give them an e-mail address or phone number they can call later if they are busy at the moment. Make sure you let them know you are an angler and not some legal beagle or environmentalist. Most of those folks fish too and they will be on your side.