Private hydropower projects above a threshold size require a license from the Federal Energy Regulatory Commission.  Many private hydropower projects in California are currently undergoing or about to begin the relicensing process.  Relicensing presents an opportunity to reduce or mitigate the environmental impacts of hydropower generation. Because renewed licenses run for thirty to fifty years, relicensing also presents substantial challenges given the likelihood of significant changes both in the environment and in our understanding of it over that time.  Two types of changes to the FERC licensing process could potentially improve the overall environmental performance of licensed facilities over time.  The first is aggregated or coordinated licensing, that is, consideration of multiple projects together, with coordination of license conditions or mitigation requirements for improved efficiency and effectiveness.  The second is flexible or adaptive licensing, that is, including in the license or in negotiated side agreements conditions that would facilitate modification of operations or mitigation efforts as needed to respond to change over time.  Both face serious practical and legal barriers, but there are also opportunities that have not yet been explored to improve coordination and adaptability.  Most notably, the Clean Water Act section 401 certification process could allow the state to push FERC toward more regionally conscious and adaptive licensing