Determination of streamflow characteristics for ungaged Texas streams using regression analysis
Brock, Suzanne Marie
Bedient, Philip B.
Master of Science
The harmonic mean, 7Q2 (7-day, 2-year low-flow), and 7Q10 are streamflow characteristics used to determine stream waste load allocations. Predictive equations for these characteristics of ungaged Texas streams are developed using multiple regression analysis to relate streamflow characteristics to basin parameters at 63 gaged streams. Gamma, LPIII (Log-Pearson type III), and mixed-LPIII distributions are used to predict the 7Q2's and 7Q10's. Basin parameters used in the analysis include contributing drainage area, channel length and slope, basin shape factor, precipitation, and hydrologic soil group. The harmonic mean regression equation included slope, precipitation, and area and had a higher adjusted R$\sp2$ than the 7Q2 and 7Q10 equations. Gamma 7Q2 and 7Q10 estimates yielded more reliable equations than LPIII and mixed-LPIII estimates. A region-based regression analysis yielded an even higher adjusted R$\sp2$ for the harmonic mean than the statewide equation, implying that regional regression equations may be more reliable than statewide equations for Texas.
Hydrology; Environmental engineering