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.