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 …