基于耦合协调度的大理河流域径流和输沙关系分析

深入研究流域水沙关系变化是解决黄河流域高质量发展关键问题的重要科学途径之一。自20世纪50年代以来,黄河中游地区实施了大规模的水土保持工程,径流和输沙显著减少,水沙关系发生变化。该研究利用Mann-Kendall趋势检验法分析了1960—2015年来大理河流域的径流输沙变化趋势,并构建基于耦合协调度理论和Pettitt检验方法的径流输沙关系变异诊断方法,识别大理河流域径流和输沙关系的突变点,并通过Copula方法进行验证。结果表明:1)大理河流域径流输沙在月尺度和年尺度呈现显著的下降趋势;2)大理河流域径流和输沙关系在1996年发生显著突变;3)径流输沙关系发生突变后,径流和输沙均明显减少,输沙的减少幅度比径流的减少幅度高29.19个百分点,径流对输沙贡献程度下降幅度为5.10%,单位径流的输沙能力降低;4)淤地坝建设和植被恢复是造成大理河流域水沙变化的主要因素,修建淤地坝和恢复植被对减少泥沙具有积极作用。研究成果可以为进一步深化理解大理河流域水沙关系变化以及水土流失治理提供依据。

Relationship between runoff and sediment load in Dali River Basin based on coupling coordination degree

Abstract: Dali River Basin locates in the middle reaches of the Yellow River Basin, to serve as an important support to the industry and agriculture in northern China. The change of runoff-sediment has become a key issue for the high-quality development of the Yellow River Basin. Since the 1950s, large-scale projects of water and soil conservation have been performed on the middle reaches of the Yellow River, such as Dali River, in order to improve the local ecological environment in the future. Runoff and sediment load have decreased significantly, and the relationship between water and sediment load has changed in recent years. In this study, Mann-Kendall trend test was used to analyze varying trend of runoff sediment load in the Dali River Basin from 1960 to 2015, and then the coordination degree theory and the Pettitt test method were used to clarify the change-point of the relationship between runoff and sediment load. Copula method was selected to verify the obtained change-point data via the joint cumulative probability of runoff and sediment load. The results show that: (1) the runoff and sediment load in the Dali River Basin indicated a significant downward trend at different time scales, such as monthly and annual scales. The variation in runoff and sediment load depended significantly on the external environment; (2) in the relationship between runoff and sediment load, the change-point occurred in 1996, indicating the year of 1996 was a turning point in the management of soil and water loss in the Dali River Basin; (3) after the change-point, both runoff and sediment load were significantly reduced. The reduction was higher than that before the change-point, where the reduction of sediment load was 29.19 percentage points higher than that of runoff, while the contribution of runoff to sediment load decreased by 5.10%, indicating the decrease in sediment transport of runoff per unit; (4) check dam construction and vegetation restoration can be the main factors for the changes of water and sediment load in the Dali River Basin. From 1998 to 2015, Normalized Difference Vegetation Index (NDVI) change in the Dali River Basin has shown a significant increase trend, indicating that the policy of returning farmland to forests has been effectively implemented in local regions. The restoration of vegetation has a positive effect on the reduction of runoff and sediment load. Most check dams have been built in the Dali River Basin, to directly intercept the sediment, while the triggered some changes of runoff, can indirectly prevent the generation and transportation of the sediment. The findings can provide a theoretical basis and promising potentials to clarify the change of water-sediment relationship, the control of soil erosion, and the soil and water conservation in the Dali River Basin, particularly in the Loess Plateau.