Derived from: Wenger, Seth J.; Luce, Charles H.; Hamlet, Alan F.; Isaak, Daniel J.; Neville, Helen M.2010.Macroscale hydrologic modeling of ecologically relevant flow metrics. Water Resources Research. 46: W09513. doi:10.1029/2009WR008839. Climate change is projected to alter the flow regimes of streams and rivers, with consequences for physical processes and aquatic organisms. To study these hydrologic changes, we have developed a database of flow metrics for streams in the western US (extent shown on the map to the left) under historical conditions and climate change scenarios. These are based on daily simulations of the Variable Infiltration Capacity (VIC) macroscale hydrologic model produced by the University of Washington Climate Impacts Group. Trout Unlimited and the US Forest Service Rocky Mountain Research Station used these model outputs to calculate a set of summary flow metrics to describe key attributes of the flow regime for each stream segment in the 1:100,000 scale National Hydrography Dataset (NHD) in the western US, excluding larger rivers. Datasets are available for the historical period 1978-1997 and future scenarios associated with the A1B emissions scenario for the 2040s and 2080s, including (1) the ensemble mean of 10 global climate models (GCMs), (2) MIROC3.2, a GCM that projects a warmer and drier summers than the ensemble mean, and (3) PCM1, a model that projects cooler and wetter summers than the ensemble mean. Please see the Dataset Description for more information and important caveats on data accuracy and appropriate use.