Figure 9 Correlation of parameter α of PDC and FFDC of 224 catchments with catchment physical characteristics CIM .
There is a relationship between parameter α of PDC and FFDC of 224 catchments and catchment physical characteristics CIM (Figure 9 ). From Figure 9 (b), it can be seen that there is a significant correlation (negative correlation) between the seasonal index - Concentration ratio index based on monthly precipitation (CIM ) and α of FFDC, but this correlation is not as tight as Pmax*αp . In order to analyze the mechanism by which CIM affects the shape of the PDC curves, we conducted further research on the correlation between values αof PDC and CIM based on the previous research conducted in Section 4.1 (α of PDC is not related to the factors mentioned that affect β ), which indicates that α of PDC has a tighter correlation with CIM (Figure 9 (a)). Therefore, based on the previous analysis of the impact of precipitation on fast flow, CIM has impacts on the curve of PDC, which in turn affects the curve shape of FFDC.
For total flow and fast flow, the base flow index (BFI ) can be considered as the main influencing factor (but not the only) on the shape of normalized FDCs (TFDC and SFDC), Pmax*αp influences the shape of FFDC curves. CIM indirectly affects the change of fast flow through influencing precipitation. However, because the precipitation process is relatively complex, CIM has more influence on the shape of PDC than on FFDC.