REGIONALIZATION OF UNIT-HYDROGRAPH PARAMETERS .1. COMPARISON OF REGRESSION-ANALYSIS TECHNIQUES

Hydrologic regionalization is a useful tool that allows for the transf er of hydrological information from gaged sites to ungaged sites. This study developed regional regression equations that relate the two par ameters in Nash's IUH model to the basin characteristics for 42 major watersheds in Taiwan. In the process of developing the regional equati ons, different regression procedures including the conventional univar iate regression, multivariate regression, and seemingly unrelated regr ession were used. Multivariate regression and seeming unrelated regres sion were applied because there exists a rather strong correlation bet ween the Nash's IUH parameters. Furthermore, a validation study was co nducted to examine the predictability of regional equations derived by different regression procedures. The study indicates that hydrologic regionalization involving several dependent variables should consider their correlations in the process of establishing the regional equatio ns. The consideration of such correlation will enhance the predictabil ity of resulting regional equations as compared with the ones from the conventional univariate regression procedure.