This bill reauthorizes federal desalination programs under existing water infrastructure law, extending support for water desalination projects in the western United States. The legislation allows the federal government to fund up to 25 percent of the costs for ocean and brackish water desalination projects in Reclamation States, with no dollar cap on federal participation, as long as state or local entities provide at least 25 percent of funding. The bill also establishes a new competitive grant program for advanced pilot desalination technologies and first-of-a-kind systems, requiring rigorous cost analyses to determine the feasibility and expense of new desalination approaches, including treatment and disposal of brine discharge. The desalination programs are reauthorized for 15 years from the bill's enactment date. The legislation primarily affects western states, water districts, and public agencies seeking to develop new water supplies through desalination technology.