渭河流域极端降雨变化趋势及其对水沙情势的影响

为探究渭河流域极端降雨变化趋势及其对水沙情势的影响,采用非参数趋势检验、突变检验和连续小波变换诊断了渭河流域1960—2019年的极端降雨指数及径流输沙序列的变异特征,通过双累积曲线法和相关分析法定量评估了流域极端降雨对水沙变化的影响。结果表明:各极端降雨指数呈阶段性波动变化,总体上PRCPTOT,RX5day和RX1day呈不显著下降趋势,R95pTOT,SDII和FSPTOT呈不显著上升趋势。各极端降雨指数均存在以4～6 a,11～12 a,28～29 a为周期的变化特征。径流与输沙量均呈显著减少趋势,分别在1993年、1999年发生突变,其中径流存在5 a和12 a的周期。各极端降雨指数均与径流、输沙量正相关,相比之下,输沙量与各极端降雨指数之间的相关系数偏低。极端降雨变化对径流与输沙量的减少具有重要影响。其中,PRCPTOT对径流减少的影响最大(29.65%),其次是RX5day(25.68%)和FSPTOT(25.95%)。PRCPTOT对输沙量减少的影响也是最大的(10.02%),其次是RX5day(7.12%)。综上,渭河流域水沙情势的变化受极端降雨的显著影响。

Effects of Precipitation Extremes Change on Streamflow and Sediment Load in Weihe River Basin

In order to explore the trend of extreme rainfall and its impact on water and sediment regime in the Weihe River Basin, we used nonparametric trend analysis, abrupt change analysis and continuous wavelet transform to diagnose the variation characteristics of extreme rainfall index, runoff and sediment transport in the Weihe River Basin from 1960 to 2019. Moreover, we quantitatively evaluated the impact of extreme rainfall on water and sediment variation in the Weihe River Basin through double cumulative curve method and correlation analysis method. The results show that: The extreme rainfall indices fluctuate over time; On the whole, PRCPTOT, RX5day, and RX1day show downward trend(p>0.05), while R95pTOT, SDII and FSPTOT show upward trend(p>0.05). In addition, each extreme rainfall index has the periodic variation characteristics of 4～6 years, 11～12 years, and 28～29 years. The annual streamflow and annual sediment load show a significant decreasing trend, with abrupt changes in 1993 and 1999, respectively. The streamflow has periods of 5 years and 12 years. On the time scale of 12 years, the changes of streamflow and extreme rainfall indices are basically synchronous. Each index is positively correlated with streamflow and sediment load. By contrast, the correlation between sediment load and extreme rainfall index is low. Extreme rainfall changes have an important impact on the reduction of runoff and sediment load. PRCPTOT has the greatest impact on streamflow reduction(29.65%), followed by RX5day(25.68%)and FSPTOT(25.95%). Similarly, PRCPTOT also has the greatest impact on the reduction of sediment load(10.02%), followed by RX5day(7.12%). In a word, the change of water and sediment regime in the Weihe River Basin is significantly affected by extreme rainfall.