Hydrologic regionalization of watersheds. II: Applications

Multiple regression analysis (MRA) and a time series model (TSM) are developed and validated for using watershed characteristics to synthesize streamflow hydrographs. Relationships between the streamflow parameters and watershed variables are evaluated by canonical correlation analysis at 94 candidate watersheds. These relationships are constructed using MRA to predict streamflow parameters at six validation stations in two main hydrologic regions. The predicted streamflow parameters are applied to synthesizing specific monthly streamflows by using the developed TSM. The synthetic hydrographs are found to be mostly improved over those found from traditional simple regression equations. Statistical properties and reliability curves of the synthetic Qs are compared with those of the historical records. The statistical properties seem to be well preserved, and the reliability curves are reasonable in one hydrologic region but somewhat biased in the other. The proposed regionalization scheme is validated and therefore considered feasible and reliable for estimating monthly streamflows at ungauged sites.