Effects of variations in precipitation extremes on sediment load in the Second Songhua River Basin, Northeast China

Purpose Soil erosion and sediment transport are often induced by a few extreme precipitation events. Currently, there is limited information on the effects of changes in precipitation extremes on river sediment load over a long time period at the basin scale. The objectives of this study were to quantify the effects of variations in precipitation extremes on sediment load in the Second Songhua River Basin (SSRB), northeast China. Materials and methods Daily precipitation data from 10 meteorological stations within the SSRB and sediment load data during 1960–2014 from the basin outlet hydrological station were collected. Six extreme precipitation indices, such as erosive precipitation (ERPTOT), wet-day precipitation (PRCPTOT), very wet day precipitation (R95pTOT), flood season precipitation (FSPTOT), maximum 1-day precipitation (RX1day) and heavy precipitation (HP), were used to detect the precipitation extremes. The Mann–Kendall non-parametric trend analysis was used to analyze the dynamic changes in precipitation extremes and sediment load. The double cumulative curve method was used to assess the effects of changes in precipitation extremes on sediment load. Results and discussion The results indicated that six extreme precipitation indices showed periodic variations from 1960 to 2014, while they did not show any significant change trend in the SSRB ( p > 0.05); however, the sediment load showed an extremely significant decreasing trend ( p < 0.01) over the past 55 years. Sediment load significantly correlated with six precipitation extremes indices ( p < 0.05). Compared with the baseline period (1960–1977), the sediment load was reduced by 1.12 × 10 6 ton per year (1977–2014). The contribution of precipitation extremes to the sediment load ranged from -22.83% to 6.97%. The corresponding contribution of the non-precipitation factor to sediment load was from 93.03% to 122.83%. Conclusions The change in precipitation extremes was not the main reason for the sediment load reduction. Sediment load reduction in the SSRB was due to the interactions between multiple factors. Non-precipitation factors, such as reservoir construction, were the main reasons for the sediment load reduction. These findings are useful to understand the variation of river sediment load and to adopt countermeasures to relieve potential risk of precipitation extremes.