应用重标度极差分析法（R/S）分析无定河流域水沙变化

河流水沙变化是降水、蒸发及下垫面条件改变的客观反映，揭示流域水沙演变规律及成因，可为水资源合理利用提供决策依据。应用R/S分析法对时变指数Hurst的计算及其检验，分析无定河流域赵石窑站和白家川站径流与输沙量时间序列的长程相关性。结果表明：两站的径流时间序列的Hurst指数分别为0.56、0.61，均大于0.5，呈现长程正相关；而两站的输沙量时间序列的变化存在差异，赵石窑站的输沙量时间序列有2个突变点，分别发生在1966和1979年，3个标度分布范围的Hurst指数分别为0.97、0.71和0.90，均明

Variation trends analysis of runoff and sediment time series based on R/S method in Wuding River Basin

Changes in runoff and sediment are caused by precipitation, evaporation, and underlying surface conditions. The policy-making basis for the water resources reasonable use was provided by revealed the variation trends of runoff and sediment time series and causes in this paper. To study the complex stochastic and undulatory property of the runoff and sediment time series, an R/S method was used. Through the time-varying Hurst index, the variation trends of runoff and sediment time series were investigated. Results showed that the Hurst indices of runoff time series were 0.56, 0.61 in Zhaoshiyao Hydrological Station and Baijiachuan Hydrological Station, a long-term positive correlation of runoff time series was showed. There were two jump points in the Hurst index of sediment time series in Zhaoshiyao Hydrological Station, occurred in 1966 and 1979, respectively, which showed fractal properties. There were three jump points in the Hurst index of sediment time series in Bjiajiachuan Hydrological Station, occurred in 1966, 1972 and 1979, with the four-scale distribution of the Hurst index of 0.59,0.41,0.99 and 0.81, respectively. The first two scale range of Hurst index was 0.5 or so, subject to Brownian motion; while the latter two scale range of Hurst index approached to 1.0, with fractal characteristics. Therefore, the runoff and sediment time series at the two hydrological stations in future will be the same trends as in the past period, i.e., with continued downward trend. Human activity is the main reason for this change.