Chemical and physical assessments of water quality are important components of evaluating watershed health. These assessments allow for an understanding of current watershed conditions and are the basis for many regulatory programs.

USGS National Water-Quality Assessment Program (NAWQA)
NAWQA provides an understanding of water-quality conditions and how those conditions may vary locally, regionally, and nationally; whether conditions are getting better or worse over time; and how natural features and human activities affect those conditions.

National Rivers and Streams Assessment (NRSA)
U.S. EPAs NRSA program will use a random sampling design to provide regional and national estimates of the condition of rivers and streams. Physical/Chemical water quality, as well as biological integrity will be assessed over time to better understand the condition of the Nation’s waters.