Two brief companion decisions of a unanimous Supreme Court, decided March 24, 1971, are of great importance to the determination of federal water rights in western states. Although deceptively simple on the surface, the opinions reaffirm the right of the United States to reserve water for federal lands independent of state water law. The opinions also set out the manner in which the water rights of national forests, wildlife preserves, parks, reservations, and other federal enclaves will be decided by holding that state courts may adjudicate all federal water rights, through varied forms of general adjudications, but that the definition of federal water rights nevertheless is a "federal question" that may always be reviewed in federal courts, including when necessary the Supreme Court. The Court defined "stream system" narrowly enough to allow courts to decide the water rights of various parties along limited segments of larger river systems and held that such limited determinations are nevertheless "general adjudications," even though rights in the larger system are not redetermined. The Court also partially resolved the conflict between western states and the federal government over water rights dating to the states' entry into the Union and dampened states' attempts to erode federal reserved water rights and to establish a late priority for federal water claims as against state claims. Finally, these decisions have probably ensured that the Supreme Court will again have federal water rights before it for adjudication in the near future.