Estimated Perennial Streams in Idaho

Perennial streams in Idaho have been modeled using regression equations for 7-day, 2-year low flows (7Q2) described in Wood and others (2009, U.S. Geological Survey Scientific Investigations Report 2009-5015). The model produces "synthetic" streams based on 10-meter resolution digitial elevation models that have been processed to agree closely with 1:24,000-scale National Hydrography Dataset flowlines. Lines having attribute PerCode = 1 represent model grid cells having 7Q2 flow estimates between 0.1 cubic feet per second (ft3/s) and 0.1 minus the standard error for the applicable regional regression equation. Lines having attribute PerCode = 2 represent model grid cells having 7Q2 flow estimates between 0.1 ft3/s and 0.1 plus the standard error for the applicable regional regression equation. Lines having attribute PerCode = 3 represent model grid cells having 7Q2 flow estimates greater than 0.1 ft3/s plus the standard error for the applicable regional regression equation. These three categories of lines indicate approximate levels of uncertainty in the model results, with lines having PerCode = 1 representing the most uncertainty, and lines having PerCode = 3 representing the least uncertainty with respect to representing a perennial stream.