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U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2009–5015

Estimating Locations of Perennial Streams in Idaho Using a Generalized Least-Squares Regression Model of 7-Day, 2-Year Low Flows

Prepared in cooperation with the Idaho Department of Environmental Quality and the Bureau of Reclamation

By Molly S. Wood, Alan Rea, Kenneth D. Skinner, and Jon E. Hortness

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Figures

Figure 1. Location of study area, eight regions, and streamflow-gaging stations in Idaho and surrounding areas used to estimate low-flow frequency statistics for unregulated streams.

Figure 2. Screen capture of spatial distribution of perennial streams, Hydrologic Unit Code boundaries, and 1:24,000-scale quadrangles from National Hydrography Dataset High-Resolution in northern Idaho.

Figure 3. Improvement of 7Q₂ flow estimates in extreme extrapolation for region 8 from the Hortness (2006) regression equation to the revised regression equation for Idaho.

Figure 4. Screen captures from U.S. Geological Survey perennial streams model showing spatial pattern of stream network in a selected area in region 8 derived from Hortness (2006) 7Q₂ regression equation and revised 7Q₂ regression equation for Idaho.

Figure 5. Screen captures from U.S. Geological Survey perennial streams model showing spatial pattern of stream network for Hydrologic Unit Code 16010201 (in region 8) derived from Hortness (2006) 7Q₂ equation and revised 7Q₂ regression equation for Idaho.

Figure 6. Screen capture of spatial distribution of modeled streams and Hydrologic Unit Code boundaries from U.S. Geological Survey perennial streams model in northern Idaho.

Figure 7. Locations of comparison points from datasets used to evaluate the U.S. Geological Survey perennial streams model for Idaho.

Tables

Table 1. Regression equations for the low-flow statistic, 7Q₂ , for unregulated streams in regions 1–8, Idaho.

Table 2. Range of values of basin characteristics used to estimate the low-flow statistic, 7Q₂ , for unregulated streams in regions 1–8, Idaho.

Table 3. Description of datasets used for evaluation of the U.S. Geological Survey perennial streams model for Idaho.

Table 4. Agreement rules for comparing independent datasets with the U.S. Geological Survey perennial streams model for Idaho.

Table 5. Classification table of accuracy of the U.S. Geological Survey perennial streams model relative to comparison datasets for Idaho.

Table 6. Agreements between the U.S. Geological Survey perennial streams model and comparison datasets by hydrologic region, Idaho and surrounding areas.

This report is available online in Portable Document Format (PDF). If you do not have the Adobe Reader, it is available for free download from Adobe Systems Incorporated.

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Send questions or comments about this report to the author, M.S. Wood, (208) 387-1320.

For more information about USGS activities in Idaho, visit the USGS Idaho Water Science Center home page.