Abstract:

Objective: The Ning-Meng reach of the upper Yellow River is a major source of sediment input, posing urgent ecological threats such as the formation of a “new suspended river” and ice-flood-induced breaches. This study aims to analyze the mechanisms and spatiotemporal patterns of sediment transport into the river in this region, and identify key hazard areas along the main channel, so as to provide scientific support for the implementation of the “Yellow River Bend” campaign under the Three-North Shelterbelt Forest Program. Method: This study focused on the Tengger Desert, Ulan Buh Desert, and Kubuqi Desert. The methods of field surveys, remote sensing interpretation, and multi-source data integration were comprehensively applied to systematically analyze the patterns of aeolian sand input into the Yellow River from these three deserts and identify the affected areas. Result: 1）Aeolian sand from the proximal deserts such as the Tengger, Ulan Buh, and Kubuqi Deserts and the underlying soft sandstone formations were the primary source of coarse sediment in the Ning-Meng reach of the Yellow River. This sediment entered the channel mainly through four processes: wind erosion, dune migration, suspension and deposition, and transport by flood events. 2）With the Toudaoguai hydrological station as the basin outlet, the sediment transport in the Ning-Meng reach from 1950 to 2023 ranged from 1.630×10⁷ t to 3.162 1×10⁸ t, with an average of 9.405×10⁷ t. The Mann-Kendall test showed a significant decreasing trend in sediment transport (P<0.01) at a rate of 1.80×10⁶ t·a^?1 during this period. 3）The amount of sediment input into the river in the Ning-Meng reach showed a gradual downward trend from 1986 to 2013. From a seasonal perspective, the sediment input from the Ulan Buh Desert was dominated by spring, with contributions of 46.8%, 24.7%, 21%, and 7.5% in spring, summer, autumn, and winter, respectively. 4）There were significant spatial differences in sediment input from the three deserts. The Ulan Buh Desert had the largest annual average input at 9.369 7×10⁶ t, followed by the Kubuqi Desert at 6.534 2×10⁶ t, and the Tengger Desert the smallest at only 7.649×10⁵ t. Conclusion: The sediment input into the Yellow River in Ning-Meng reach exhibits significant spatial and temporal heterogeneity: it predominantly occurs in the spring and shows an annual decline over time. In space, it forms a gradient pattern of sediment input into the Yellow River with Ulan Buh Desert>Kubuqi Desert>Tengger Desert. This study provides a scientific basis for desertification prevention and ecological restoration in the sandy hazard areas along the Ning-Meng reach of the Yellow River, which holds practical significance for ensuring the stability of the Yellow River and the ecological security of the basin.

Key words: Ning-Meng reach, wind sand into yellow, spatiotemporal characteristics, sediment transport, upper Yellow River