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.These files cover portions of four major river basins in the Western US: the Columbia (plus coastal drainages), the Upper Colorado, the Great Basin, and selected portions of the Upper Missouri (Figure 1). The coverage area was defined to encompass the historical range of inland cutthroat trout, but for practical reasons the Rio Grande and the Arkansas basins were excluded. Rivers with a drainage area larger than about 250 km2 are not covered in the dataset. This is because our method for flow routing (Wenger et al. 2010a) does not include travel time in the river channel. This produces reasonable results for streams of small to moderate drainage, in which flow responds to precipitation within hours rather than days, but it is not realistic for larger rivers. In addition, routed flows for large rivers in some regions (particularly the Pacific Northwest), are already available from the Climate Impacts Group.
