NASQAN National Stream Quality Accounting Network
Data collected by the NASQAN program prior to 1996 can be obtained from several sources provided here. Two of the sources (NWISWEb and NWIS Water-Quality Web Services) are also the place to obtain data occasionally collected at NASQAN sites by USGS programs other than NASQAN. These two sources provide alternative interfaces to the same database. Older NASQAN data may have been analyzed by different methods and detection and reporting limits have changed over the years. See Data from Selected U.S. Geological Survey National Stream Water-Quality Monitoring Networks and Streamflow and Nutrient Fluxes of the Mississippi-Atchafalaya River Basin and Subbasins for the Period of Record Through 2005 for a discussion of the history of the early years of NASQAN and some of the issues associated with aggregating older data with newer data.