Is the branch slate bottom? If so a “key hole” cut will need to be made across the slate to keep water from seeping underneath. I had an amazingly strong spring and was considering a nice pond when I lived in Adair. I fixed that urge by selling the property. :-)
This is in the Trans-Bluegrass, north of Lexington. It's all limestone and clay. The clay is so impermeable that we all have to have ponds instead of leach fields for our sewage. The problem lies in the limestone-- if there's a gap, it can leak badly. Most recently, two locals have tried ponds. One went perfect. The other failed to hold water in the test dig and the project was abandoned. The two ponds are less than 1/4 mile apart, and to the eyeball looked identical.
