What is a stream?

摘要

The Clean Water Act (CWA) is the primary instrument for regulating "waters of the United States" with a goal "to restore and maintain the chemical, physical, and biological integrity of the Nation's waters." After almost four decades, the precise definition of "the Nation's waters" or "waters of the United States" remains unclear, and the geographic scope of the CWA shifts in response to legal challenges and rulings.