Take a look at the Pond Boss book store: http://www.pondboss.com/books.html

Consider buying "Perfect Pond... Want one?" which I personally own and think is excellent. There are also several other earthen pond related books in the store as well. They should be a great start.

Also, seek out your local NRCS agent. Some are not very helpful but others can be a complete goldmine of free information and help.