Stations in the USGS's National Stream Quality Accounting Network (NASQAN)

This is a point coverage of stations in the U.S. Geological Survey's National Stream Quality Accounting Network (NASQAN). NASQAN was established in 1973. Water-quality data currently is collected at NASQAN sites on bimonthly and quarterly intervals. However, some of the bimonthly stations will be sampled only five times a year beginning in 1992. Separate coverages exist for the conterminous United States, Alaska, Hawaii/Guam, and Puerto Rico. The coverages attempt to represent all of the stations that are or have been in the network (some are inactive or discontinued) as of spring 1992.