## Region Regression Equations by State

### Washington

**Low Flow (Qlow):** To find the low flow regional regression equation, use this document from USGS.

- Equation 11 (p. 32) is the correct low flow equation.
- Reformatted to fit sqlBRATâ€™s terminology, it becomes 8.48*.0001*((DRNAREA**1.17)*(PRECIP**1.23))
- Put the regression equation into the appropriate area on the Google Sheet that represents your watershed.

**High Flow (Q2):** To find the high flow regional regression equation, use this document from USGS.

- Use Figure 16 (p. 29) to identify what regression region your watershed is in.
- Use Table 6 (p. 36) to find the regression equation for your region. This will be in the 3rd column, titled
*Form of the regression equation* - Replace all of the constants and coefficients in the equation with the values from the table. We recommend an exceedance probability of 0.5.
- Replace the variables A, P, and CAN with the correct terminology used in sqlBRAT. A becomes
**DRNAREA**, P becomes**PRECIP**, and CAN becomes**CANOPY_PCT**. - Reformat the rest of the equation so that sqlBRAT can understand it. Make sure that parenthesis are in the correct place, exponents become **, and multiplication becomes *.
- Put the regression equation into the appropriate area on the Google Sheet that represents your watershed.