Sorry, I don't have any suggestions, but it sure does sound like a great project. Too bad there isn't a "Rent A Beaver" store near you. :-)

Googling ~ site:.gov building design "farm ponds" ~ pulls up a lot of interesting stuff. Substituting hobby for farm gets a couple of ghits and substituting koi for farm gets 72 ghits if I recall. When I was a kid the government was often sending out pamphlets about ponds which gave me the idea for this search.

As I recall from my youth sediment was a problem when building ponds in small streams. Perhaps some of the government sites offer preventive measures.

We have had several discussions on this from different points of interest that might be helpful and searches here and on the internet will give you a lot of info. In your case we need to know a bit more about the topography of the area surroundinng the proposed pond. If it is flat you may need to do quite a bit of digging or you will wind up with a marsh. That is the main complaint about beaver dams. Can you describe it in detail or show some photos?

You can't beat calling Fish & Game. They're likely to send out the best people in the world to help with all aspects of design from testing soil to plant selection. You still get to control the kind of pond. Many years ago they would even kick in some money, don't know if they still do. We all benefit from better wildlife habitat.

Messing around with streams is regulated. I think in every state streams and sometimes the banks are not owned by the owner of the surrounding land. But of course most property owners think they do own the stream. That can create serious legal problems. Who owns the stream normally has to do with the stream size. Rarely there's any list and a judge would have to decide on a case by case basis if needed. Way better imo to have Fish & Game involved at the start than knocking on your door later...and they will. Had a guy dam a small stream on a property next to mine once and Fish & Game was there in less than a week. The guy made a complete mess, must have been 10 yards of concrete, forms buckled, a mess. F&G still worked with him to try and fix it in the easiest way possible instead of just fining him thousands. They're on your side unless you think you have the right to break the law which I'm sure you don't.

Have to agree with waterbug... a friend of mine built a large concrete dam on a small stream on his 80 acre property to create a 5 acre pond and ended up with fines in excess of $500,000. Obviously he had/has money so he fought the legal battle and was allowed to keep the pond and only had to pay $75,000 in fines. His motto is "it's easier to ask for forgiveness than it is to ask for permission"...