2002 marks the 30th anniversary of one of the most significant environmental laws in American history, the Clean Water Act (CWA). The CWA has had remarkable success, reversing years of neglect and outright abuse of the nation’s waters. But challenges remain as attention turns to the thorny issue of cleaning up nonpoint sources of pollution. Included in this issue is a discussion of the challenge of cleaning up nonpoint pollutant sources, how regulators in California are attempting to mitigate the effects of agricultural runoff, the growing nexus between water quality and water supply and the current efforts to more clearly define the law’s linchpin of navigable waters.