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New York Water Science Center 

The Hydrologic Benchmark Network

By Michael R. McHale and Jason Siemion


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The Hydrologic Benchmark Network (HBN) consists of 37 watersheds that provide long-term measurements of streamflow and water quality in areas that are minimally affected by human activities. In 2011 measurements of aquatic biology and soil chemistry were added to the network. All of these data are used to study long-term trends in surface water flow, water chemistry, aquatic biology, and soil chemistry and as a benchmark against which to compare changes in flow and chemistry in developed watersheds.

In 1962, Luna B. Leopold, then Chief Hydrologist of the U.S. Geological Survey (USGS), proposed the establishment of a network of “hydrologic benchmarks” on the nation’s rivers (Leopold, 1962). The main purpose of the Hydrologic Benchmark Network (HBN) is to provide a long-term database to track changes in the flow and water quality of undisturbed streams and rivers (rivers draining undeveloped lands), and to serve as a reference for discerning natural from human-induced changes in river ecosystems. In the ever-changing landscape of the North American continent, there are few medium- to large-scale watersheds that remain largely undisturbed. The HBN is the only nationwide network of environmental monitoring stations that tracks the health of rivers draining medium sized, undisturbed basins in the United States. HBN watersheds range in size from 2 mi2 to 254 mi2 though one watershed has an area close to 2,000 mi2. HBN watersheds are larger than typical research watersheds in which most ecosystem research is conducted, but are small enough to be responsive to anthropogenic atmospheric inputs and climate change. The HBN thus provides a frame of reference to evaluate changes in river chemistry and flow patterns in large or developed watersheds, such as those commonly sampled as part of State and Federal monitoring programs.

First posted November, 2013

    Related Links
      Related Publications
    • McHale, M.R., Siemion, Jason, Lawrence, G.B., and Mast, M.A., 2014, Long-term soil monitoring at U.S. Geological Survey reference watersheds: U.S. Geological Survey Fact Sheet 2014-3002, 2 p.,

  • Clark, G.M., Mueller, D.K., and Mast, M.A., 2000a, Nutrient concentrations and yields in undeveloped basins of the United States: Journal of the American Water Resources Association, v. 36, no. 4, p. 849-860.

  • Clark, M.L., Eddy-Miller, C.A., and Mast, M.A., 2000b, Environmental characteristics and water quality of Hydrologic Benchmark Stations in the western United States, 1963-95: U.S. Geological Survey 1173-C, 115 p. [Circular].

  • Clow, D. W., and M. A. Mast (1999), Long-Term Trends in Stream Water and Precipitation Chemistry at Five Headwater Basins in the Northeastern United States, Water Resour. Res., 35(2), 541–554.

  • Clow, D.W., and Mast, M.A., in press, Mechanisms for chemostatic behavior in catchments: implications for CO2 consumption by mineral weathering: Chemical Geology.

  • Cobb, E.D., and Bieseker, J.E., 1971, The National Hydrologic Benchmark Network: U.S. Geological Survey 460-D, 38 p. [Circ.].

  • Coplen, T.B., and Kendall, C., 2000, Stable hydrogen and oxygen isotope ratios for selected sites of the U.S. Geological Survey's NASQAN and Benchmark surface-water networks: U.S. Geological Survey 00-160 [Open-File Report].

  • Evans, C., and Davies, T.D., 1998, Causes of concentration/discharge hysteresis and its potential as a tool for analysis of episode chemistry: WRR, v. 34, no. 1, p. 129-137.

  • Godsey, S., Kirchner, J.W., and Clow, D.W., 2009, Concentration-discharge relationships reflect chemostatic characteristics of catchments: Hydrological Processes, v. 23, p. 1844-1864, doi: 10.1002/hyp.7315.

  • Hainly, R.A., and Ritter, J.R., 1986, Areal and temporal variability of selected water-quality characteristics in two hydrologic-benchmark basins in the northeastern United States: U.S. Geological Survey 85-4025, 22 p. [Water-Resources Investigation Report].

  • Kendall, C., and Coplen, T.B., 2001, Distribution of oxygen-18 and deuterium in river water across the United States: Hydrological Processes, v. 15, p. 1363-1393, doi: 10.1002/hyp.217.

  • Landwehr, J.M. and Slack, J.R., 1992 (revised 1993), WATER FACT SHEET Hydro-Climatic Data Network (HCDN): A U. S. Geological Survey streamflow data set for the United States for the study of climate fluctuations, 1874-1988: U.S. Geological Survey Open-File Report 92-632, 2 pages.

  • Lawrence, C.L., 1987, Streamflow Characteristics at Hydrologic Benchmark Stations: U.S. Geological Survey 941, 123 p. [Circ.]. Leopold, L.B., 1962, A national network of hydrologic bench marks: U.S. Geological Survey 460-B, 4 p. [Circular].

  • Mast, M.A., and Clow, D.W., 2000, Environmental characteristics and water quality of Hydrologic Benchmark Stations in the western United States, 1963-95: U.S. Geological Survey 1173-D, 114 p. [Circular].

  • Mast, M.A., and Turk, J.T., 1999a, Environmental characteristics and water quality of Hydrologic Benchmark Stations in the eastern United States, 1963-95: U.S. Geological Survey 1173-A, 158 p. [Circular].

  • Mast, M.A., and Turk, J.T., 1999b, Environmental characteristics and water quality of Hydrologic Benchmark Stations in the Midwestern United States, 1963-95: U.S. Geological Survey 1173-B, 130 p. [Circular].

  • Mueller, D.K., and Spahr, N.E., 2006, Nutrients in streams and rivers across the nation -- 1992-2001: U.S. Geological Survey, 44 p. [Scientific Investigations Report].

  • Robertson, D.M., and Roerish, E.D., 1999, Influence of various water quality samping strategies on load estimates for small streams: WRR, v. 35, no. 12, p. 3747-3759.

  • Slack, J.R. and Landwehr, J.M., 1992, Hydro-Climatic Data Network (HCDN): A U.S. Geological Survey Streamflow Data Set for the United States for the study of climate variations, 1874-1988: U.S. Geological Survey Open-File Report 92-129, 193 pages, with diskette. URL

  • Smith, R.A., Alexander, R.B., and Schwarz, G.E., 2003, Natural background concentrations of nutrients in streams and rivers of the conterminous United States: Environmental Science & Technology, v. 37, no. 14, p. 3039-3047.

For additional information contact:
(1) Director
U.S. Geological Survey
Troy Program Office
New York Water Science Center
425 Jordan Road
Troy, NY 12180

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