4.3 Correlating parameters with catchment physical characteristics
Regression was conducted with the shape parameters α of TFDC, FFDC, and SFDC and some climate and geographical features. As shown inFigure 8 (a) and (b), it is clear that the parameters αof TFDC and SFDC is closely related to the base flow index (BFI ) between watersheds, where BFI is a common indicator of the response features of runoff in watersheds, reflecting the comprehensive impact of local geographical and climate characteristics. In addition, it can be found that the shape changes of TFDC and SFDC at 224 hydrological stations monotonically increase with the increase ofBFI , which means that the spatial changes of TFDCs and SFDCs are controlled by climate and watershed characteristics that affect the division of runoff into fast and slow flow. Watersheds with largerBFI should have a larger proportion of slow flow, so the curves of TFDC or SFDC tend to be flatter. Therefore, BFI can be used to estimate the value of α .