The U.S. EPA has developed approaches for implementing a statistically valid survey for assessing the nation's waters. These resources are specific to states but provide a framework approach to help build national monitoring program. The National Aquatic Resource Surveys (NARS) use randomized sampling designs, core indicators, and consistent monitoring methods and lab protocols to provide statistically-defensible assessments of water quality at the national scale. As the surveys repeat, the U.S. EPA will be able to track changes over time and advance its understanding of important regional and national patterns in water quality.