Data from selected U.S. Geological Survey national stream water-quality monitoring networks (WQN) on CD-ROM

Abstract

During the past 30 years, the U.S. Geological Survey (USGS) has operated two national stream water-quality networks, the Hydrologic Benchmark Network (HBN) and the National Stream Quality Accounting Network (NASQAN). These networks (Fig. 1) were established to provide national and regional descriptions of stream water-quality conditions and trends, based on uniform monitoring of selected watersheds throughout the United States, and to improve our understanding of the effects of the natural environment and human activities on water quality. The HBN, consisting of 63 relatively small, minimally-disturbed watersheds, provides data for investigating naturally-induced changes in streamflow and water quality and the effects of airborne substances on water quality. These watersheds range in size from 2 to 2,000 square miles with a median drainage basin size of 57 square miles. NASQAN, consisting of 618 larger, more culturallyinfluenced watersheds, provides information for tracking water-quality conditions in major U.S. rivers and streams. Drainage basins range in size from 1 square mile to 1.2 million square miles with a median drainage basin size of about 4,000 square miles. NASQAN and HBN watersheds represent a diverse set of climatic, physiographic, and cultural characteristics. Stream water-quality measurements are available for the approximate periods 1973 to 1995 for NASQAN and 1962 to 1995 for HBN. The data reflect sampling for a variety of water properties over a wide range of streamflow conditions using relatively consistent sampling and analytical methods. Figures 2 and 3 display the number of water-quality analyses by year for NASQAN and HBN, respectively. These data, collectively referred to as Water-Quality Networks (WQN), are contained in the two-CD-ROM set USGS Digital Data Series DDS-37, “Data from Selected U.S. Geological Survey National Stream Water-Quality Monitoring Networks (WQN),” by R.B. Alexander, J.R. Slack, A.S. Ludtke, K.K. Fitzgerald, and T.L. Schertz.