The US Geological Survey started, in a pilot phase, a program to provide nationally consistent information on the status and trends in the quality of the nation's fresh water. The program also intends to identify and describe the relationships between both the status and trends in water quality as they relate to natural factors, and the history of land-use, and land- and waste-management practices. The program is organized into hydrologically based study units and, for the study of surface water, involves a combination of fixed-station, synoptic and intensive study approaches. Network design considerations are discussed.