This page links to information that is available about hydro relicensing.
This is the Federal Energy Regulatory Commission (FERC) Official Site. It contains links to details about relicensing.
This is the web site of the National Hydropower Association, which is the industry trade group for hydropower generation. It is a good source for industry views on hydropower. They have a document called Relicensing Hydroelectric Projects, which is worth studying.
American Rivers is a river advocacy group with a lot of relevant information about dam removal, hydro relicensing, and general river advocacy, including a relicensing toolkit.