Diagnoses of runoff-sediment relationship based on variable diagnostic method-variable step length sliding correlation coefficient method in Ning-Meng reach

Due to the discordant runoff-sediment relationship, there appears serious sedimentation in Ning-Meng reach in recent years. Especially in Inner Mongolia, the main stream and tributaries are “suspend rive”, which safety risk are outstanding. For the complicated runoff-sediment relationship, this paper proposes a new variable diagnostic method-variable step length sliding correlation coefficient method, to diagnose the variation features of runoff-sediment relationship in Ning-Meng reach. According to analyze its annual sequences of runoff and sediment, change-points will be got: 1964 and 1992, and their mutations are quite consistent. By taking range of value and extent of change as indexes, the influence of water projects on downstream runoff-sediment relationship is clarified, which is gradually weaken from upstream to downstream. Using reason analysis, at last, change-points are analyzed. The result shows water transfer and generate electricity of water projects in Yellow River upstream altered water flow process, that the amounts of flow peak in summer decreased acutely, and the influence on downstream is accumulated, and the relationship changed qualitatively since hydrological events occurred in 1964 and 1992. Simultaneously, this approach may provide reference and application value in other analysis of regularity of sediment and water.