Multi-Time Scale Analysis of Runoff Variation of Kaidu River over Past 60 Years

The pattern analysis of the long-sequence river runoff evolution holds crucial importance for the scientific planning and rational utilization of surface water resources. This study was grounded in runoff data from the Kaidu River over the past 60 years or above. By applying techniques such as simple linear regression, non-parametric testing, R/S analysis, and wavelet analysis, it delved into the runoff variation patterns across two time scales: the multi-year scale and the seasonal scale.​ The results reveal that the runoff demonstrates a pronounced upward trend at the multi-year scale, along with in spring, autumn, and winter seasons. Conversely, the increasing tendency of runoff in summer is relatively unremarkable. The computed values of the statistical test indices<italic> Z </italic>and <italic>β </italic>are consistent with the outcomes of the linear regression analysis. The mutation point of runoff at the multi-year scale is identified as 1996. At the seasonal scales of spring, summer, autumn, and winter, the inflection points for the transition between wet and dry periods of runoff are 1996, 1996, 1994, and 1994, respectively. At the multi-year scale, the Hurst index of runoff stands at 0.865. At the seasonal scales of spring, summer, autumn, and winter, the Hurst indices of runoff are 0.653, 0.792, 0.852, and 0.912, respectively, with all these values surpassing 0.5. It suggests that the runoff will persist in an upward trajectory in the future. At the multi-year scale, the runoff features change cycles of 14 years and 25 years. At the seasonal scale, the first-order principal cycle of runoff fluctuates in the range of 14~15 years. The research findings provide a technical reference for the scientific utilization of surface water resources and ecological conservation within the basin.