Table S1.
Regression model results for each two-digit HUC derived from the hydraulic geometry relationship between that natural log of discharge (cubic meters per year) and both width (meters) and velocity (meters per second)
| Width | Velocity | ||||||||
| HUC | No. of sites | No. of measurements | SO range | Slope | Intercept | r2 | Slope | Intercept | r2 |
| 01 | 458 | 36,977 | 1–7 | 0.484 (0.469–0.499) | 1.953 (1.915–1.991) | 0.90 | 0.172 (0.159–0.186) | −1.152 (−1.186 to 1.117) | 0.58 |
| 02 | 1,589 | 203,570 | 1–7 | 0.484 (0.475–0.493) | 2.154 (2.134–2.174) | 0.88 | 0.192 (0.182–0.202) | −1.255 (−1.277 to 1.234) | 0.49 |
| 03 | 2,069 | 224,935 | 1–8 | 0.47 (0.461–0.479) | 2.106 (2.081–2.13) | 0.83 | 0.14 (0.13–0.149) | −1.419 (−1.445 to 1.392) | 0.5 |
| 04 | 653 | 58,818 | 1–7 | 0.501 (0.486–0.516) | 2.001 (1.965–2.037) | 0.87 | 0.161 (0.142–0.179) | −1.156 (−1.201 to 1.11) | 0.45 |
| 05 | 1,066 | 149,787 | 1–9 | 0.475 (0.465–0.486) | 1.975 (1.944–2.007) | 0.88 | 0.132 (0.123–0.141) | −1.128 (−1.156 to 1.1) | 0.42 |
| 06 | 323 | 31,355 | 1–8 | 0.482 (0.463–0.5) | 2.086 (2.039–2.133) | 0.89 | 0.148 (0.127–0.168) | −1.186 (−1.24 to 1.132) | 0.38 |
| 07 | 892 | 121,268 | 1–10 | 0.504 (0.493–0.515) | 1.901 (1.868–1.934) | 0.90 | 0.142 (0.132–0.152) | −1.187 (−1.217 to 1.156) | 0.45 |
| 08 | 257 | 25,334 | 1–10 | 0.452 (0.424–0.481) | 2.089 (1.988–2.19) | 0.79 | 0.167 (0.132–0.202) | −1.538 (−1.66 to 1.416) | 0.26 |
| 09 | 133 | 17,242 | 1–7 | 0.495 (0.46–0.531) | 1.802 (1.707–1.897) | 0.85 | 0.147 (0.113–0.18) | −1.233 (−1.322 to 1.144) | 0.36 |
| 10 | 1,265 | 170,656 | 1–9 | 0.502 (0.491–0.512) | 1.802 (1.776–1.827) | 0.88 | 0.128 (0.119–0.137) | −0.978 (−0.999 to 0.956) | 0.39 |
| 11 | 689 | 80,126 | 1–9 | 0.47 (0.456–0.483) | 1.972 (1.932–2.011) | 0.87 | 0.107 (0.095–0.119) | −1.08 (−1.115 to 1.045) | 0.31 |
| 12 | 459 | 78,868 | 1–7 | 0.465 (0.441–0.489) | 1.783 (1.714–1.852) | 0.77 | 0.111 (0.091–0.132) | −1.156 (−1.216 to 1.095) | 0.2 |
| 13 | 134 | 18,253 | 1–8 | 0.549 (0.516–0.582) | 1.906 (1.837–1.975) | 0.89 | 0.141 (0.107–0.175) | −0.777 (−0.848 to 0.705) | 0.34 |
| 14 | 480 | 56,148 | 1–8 | 0.516 (0.502–0.529) | 1.769 (1.742–1.797) | 0.92 | 0.166 (0.155–0.177) | −0.705 (−0.728 to 0.682) | 0.64 |
| 15 | 306 | 33,320 | 1–9 | 0.503 (0.481–0.526) | 1.897 (1.848–1.946) | 0.86 | 0.155 (0.135–0.175) | −0.903 (−0.947–0.86) | 0.42 |
| 16 | 327 | 49,752 | 1–7 | 0.518 (0.501–0.535) | 1.754 (1.721–1.786) | 0.92 | 0.148 (0.129–0.167) | −0.786 (−0.822 to 0.75) | 0.42 |
| 17 Dry | 784 | 71,445 | 1–8 | 0.493 (0.481–0.505) | 1.86 (1.83–1.89) | 0.90 | 0.145 (0.133–0.158) | −0.784 (−0.817 to 0.752) | 0.4 |
| 17 Coast | 524 | 52,978 | 1–8 | 0.465 (0.451–0.479) | 1.932 (1.893–1.971) | 0.89 | 0.184 (0.167–0.2) | −0.98 (−1.026 to 0.933) | 0.48 |
| 18 Dry | 571 | 67,046 | 1–7 | 0.476 (0.46–0.491) | 1.778 (1.743–1.814) | 0.86 | 0.14 (0.124–0.156) | −0.928 (−0.964 to 0.892) | 0.34 |
Values in parentheses represent the fifth–95th percentiles derived from a bootstrapped regression with replacement. All regression models were statistically significant to P < 0.001. All data used to derive these equations are available with the USGS NWIS (waterdata.usgs.gov/nwis).