Abstract:Study on the effects of extreme precipitation events on runoff and sediment load not only can reveal the mechanism of runoff and sediment, but also provide important scientific support for basin disaster warning. Currently, there is limited information on the effects of extremes precipitation events on river sediment load. Thus, Songhua River Basin (SRB), located in the northeast of China was selected as study area, and daily precipitation data from 43 meteorological stations within and surrounding the SRB and sediment load from Kiamusze hydrologic station during 1960—2014 were collected. Seven extreme precipitation indices, including maximum 1-day precipitation (RX1day), maximum 5-day precipitation (RX5day), simple daily intensity index (SDII), strong rainfall more than 95% points value (P95pTOT), heavy precipitation (HP), rainstorm precipitation (RSP) and flood season precipitation (FSPTOT)) were chosen to quantify precipitation extremes. The Mann-Kendall’s non-parametric trend analysis method and wavelet periodic analysis method were used to analyze the dynamic change of precipitation extremes and sediment load. Double mass curve method was used to assess the effect of extreme precipitation events on sediment load change. The results showed as follows: there was no significant change trend of the seven precipitation extreme indices during 1960—2014;while there existed 16~20a main period and 5~6a minor period. Meanwhile, the change trend of sediment load in Kiamusze hydrologic station was similar with the precipitation extremes. The precipitation extreme indices had highly significant correlation with sediment load (p<0.01) in the SRB, among which correction between sediment load and RX5day and P95pTOT was the most significant. The abrupt change by double mass curve method indicated that the abrupt change point between sediment load and each extreme precipitation index occurred in 1977. Compared with the baseline period in 1960—1977, the effects of precipitation extreme indices on the sediment load were ranged from 3.09% to 15.24% in 1978—2014, in which the effect of SDII was the highest with 15.24%, followed by FSPTOT with 14.81% and RX5day with 14.34%. These findings would provide useful information for forecasting sediment disaster and taking measures in conserving soil and water in the SRB.
