The USGS Hydrologic Benchmark Network (HBN)

The Neversink River near Claryville, N.Y.

HBN Station Locations

The Hydrologic Benchmark Network (HBN) was established in 1963 to provide long-term measurements of streamflow and water quality in areas that are minimally affected by human activities. These data are used to study long-term trends in surface water flow and water chemistry and as a benchmark against which to compare changes in flow and chemistry in developed watersheds. At its peak the network consisted of 58 drainage basins in 39 States. Over time, changes in funding and land use within the watersheds reduced the number of stations and samples collected by HBN. In the mid-1990s, the USGS conducted a complete review of the network, and selected 5 eastern stations to conduct a pilot study to assess the optimum sampling strategy for assessing long-and short-term trends. In 2003, the USGS re-established a 17-station water-quality and 36-station discharge monitoring network with a new design that allows tracking of trends in water quality at a range of river flow conditions. Additional stations are anticipated to be added to the network as funding allows.

HBN is the only network in the world that tracks long-term trends in water quality from undeveloped medium-size watersheds (50-250 square miles in area). The re-vitalization of the HBN program has allowed (1) assessment of trends in discharge and stream chemistry through the range in flow conditions at each site (2) investigation of concentration-discharge relationships for specific constituents through time, and (3) examination of the relation between atmospheric-deposition chemistry and stream chemistry through time. HBN basins are of appropriate size for detecting changes in ecosystem processes at the landscape scale caused by acidic deposition, excess nutrient deposition, and climate change. They are larger than typical research watersheds where most process-oriented work has been conducted making them more relevant to resource managers. HBN provides a benchmark against which to compare changes in chemistry and hydrology at larger scales, such as those found in the USGS NAWQA and NASQAN networks, which have been affected by land-use changes and water diversions.

Although the USGS provides funding for the Hydrologic Benchmark Network, the network has placed a priority on building partnerships with other government agencies and academia. HBN is currently collaborating with the National Park Service, the National Forest Service, Penn State, and Vermillion Community College.