Figure 3 Values ofR2 and Nse of the mixed gamma
distribution fitting to normalized duration curves.
The upper and lower whiskers
represent the maximum and minimum values and the upper and lower lines
of the box represent the third and first quartiles.
Among 698 weather stations and
224 hydrological stations, the 75% of the estimated values ofNse and R2 exceed 0.81 and the minimum
values are greater than 0.6. This reflects that the mixed gamma
distribution can perfectly capture the shape of PDC and FDCs.
From different hydrological stations’ distribution of Nse andR2 in FDC, it can be seen that there is a
difference. The values of R2 and Nse of
some stations are relative low, indicating that the fitting effect of
FDC is not very good at certain hydrological stations or in certain
years. On the other hand, the fitting performance of PDCs and FFDCs is
superior to that of TFDCs and SFDCs. It may be due to the fact that the
gamma fitted data should meet the requirements of independently
identically distribution, which presents the characteristic of the
random-like properties. Precipitation and surface runoff processes
include more complex stochastic processes, which are more able to
reflect this randomness.