James R. Slack

Data from selected U.S. Geological Survey National Stream Water Quality Monitoring Networks

A nationally consistent and well-documented collection of water quality and quantity data compiled during the past 30 years for streams and rivers in the United States is now available on CD-ROM and accessible over the World Wide Web. The data include measurements from two U.S. Geological Survey (USGS) national networks for 122 physical, chemical, and biological properties of water collected at 680 monitoring stations from 1962 to 1995, quality assurance information that describes the sample collection agencies, laboratories, analytical methods, and estimates of laboratory measurement error (bias and variance), and information on selected cultural and natural characteristics of the station watersheds. The data are easily accessed via user-supplied software including Web browser, spreadsheet, and word processor, or may be queried and printed according to user-specified criteria using the supplied retrieval software on CD-ROM. The water quality data serve a variety of scientific uses including research and educational applications related to trend detection, flux estimation, investigations of the effects of the natural environment and cultural sources on water quality, and the development of statistical methods for designing efficient monitoring networks and interpreting water resources data.

SEASONAL AND REGIONAL CHARACTERISTICS OF U.S. STREAMFLOW TRENDS IN THE UNITED STATES FROM 1940 TO 1999

J. R. Mather (1981) observed that runoff (streamflow) constitutes a significant phase of the hydrologic cycle. He also noted that it takes at least 15-25 years of systematic observations to characterize statistically the spatial and temporal patterns in streamflow. With this in mind, a recent assessment of temporal trends in streamflow (Lins and Slack, 1999) is updated to encompass the 60-year period 1940-1999, using data from 435 climate-sensitive stream-gauging stations and expanded to include regional and seasonal characteristics. The previously documented pattern of increasing discharge in the low to moderate range of flows is corroborated, with this pattern being most pronounced in the central two-thirds of the U.S. and to a lesser extent in the eastern coastal regions and in the Great Basin. Relatively few trends are observed in the annual maximum flow. No systematic shift in the timing of the annual minimum, median, or maximum flow is detected in any region on a monthly time scale. The observed increases in low to moderate streamflows, typical of the warm and transitional seasons, are consistent with documented trends in warm and transition season precipitation, and indicate that natural U.S. surface water supply has increased without a concomitant increase in flooding.