A Decree of the Supreme Court of the United States, entered in 1954, established the position of Dela-ware River Master within the U.S. Geological Survey (USGS). In addition, the Decree authorizes diver-sions of water from the Delaware River Basin and requires compensating releases from certain reservoirs, owned by New York City, to be made under the supervision and direction of the River Master. The Decree stipulates that the River Master will furnish reports to the Court, not less frequently than annually. This report is the 51st Annual Report of the River Master of the Delaware River. It covers the 2004 River Mas-ter report year; that is, the period from December 1, 2003, to November 30, 2004.