I have had a pond built on a creek, and can relate my experience on such a project. First, find someone that knows how to build a good dam. I've had a little experience with a track hoe and dozer, but would not attempt such a project myself. I'm not to far from your area, and can tell you that even with good clay, your dam needs to be cored and properly compacted with good emergency OV and relief pipe. I don't know what your contributing watershed acreage is, but heavy rain events can recycle all the water in a small pond on a creek. A good percentage of your fish population can definely be transient. Also, the topography is important. Escavation of a basin area can be very expensive. Contributing fish species from upstream flow can be a concern also. On the positive side, you pond will generally stay full. And, if your watershed is small, you may not have to face some of the concerns that I have mentioned.
