Scientific Investigations Report 2009–5015
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2009–5015
Table 1. Regression equations for the low-flow statistic, 7Q2 , for unregulated streams in regions 1–8, Idaho.
[Locations of regions are shown in figure 1. Standard error of prediction: Values determined using error transformation equations in Riggs (1968). Abbreviations: 7Q2, 7-day 2-year low flow, in cubic feet per second; A, drainage area, in square miles; BS, basin slope, in percent; E, mean elevation, in feet; P, mean annual precipitation, in inches; R, basin relief, in feet; S50, slopes greater than 50 percent in percentage of drainage area; V, surficial volcanic rocks, in percentage of drainage area; W, water in percentage of drainage area]
| Region | 7Q2 regression equation | Standard error of prediction | |||
|---|---|---|---|---|---|
| Original (Hortness, 2006) | Revised | log10 | Percent | ||
| 1 | 7Q2 = 0.731A0.613(W+1)0.907 | 7Q2 = 0.300A0.879 | 0.271 | +86.7 to -46.4 | |
| 12 | 7Q2 = 0.000153A1.04P1.92 | No change | 0.253 | +78.9 to -44.1 | |
| 3 | 7Q2 = 0.00953A0.392(R/1,000)3.36 | 7Q2 = 0.0214A0.971 | 0.277 | +236 to -70.2 | |
| 14 | 7Q2 = 0.0000215A1.04P2.41 | No change | 0.341 | +119 to -54.4 | |
| 5 | 7Q2 = 0.000453A1.04(V+1)1.51 | 7Q2 = 0.334A0.963 | 0.249 | +77.3 to -43.6 | |
| 16 | 7Q2 = 0.000133A1.05P2.10 | No change | 0.243 | +75.0 to -42.9 | |
| 7 | 7Q2 = 0.0329A0.678(S50+1)0.796 | 7Q2 = 0.0000115A0.837(E/1000)4.658 | 0.577 | +277 to -73.5 | |
| 8 | 7Q2 = 3.86A0.930BS-0.648 | 7Q2 = 0.00181A0.981P1.515 | 0.331 | +116 to -53.4 | |
1Denotes region with original Hortness (2006) equation.
U.S. Department of the Interior | U.S. Geological Survey
URL: http://pubs.usgs.gov/sir/2009/5015
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