塔里木河中游河道特征断面演变特性

[Objective] This study aims to quantitatively identify the main hydrological driving factors of channel morphological changes in the middle reaches of the Tarim River; to be specific, the effects of discharge, daily discharge variation, sediment concentration, and daily sediment concentration variation on channel erosion-deposition dynamics. It also aims to quantify the seasonal relationships between key driving factors and morphological responses in different hydrological periods (dry season before flood, medium-water season before flood, flood season, and post-flood season), and to clarify the differentiated morphological evolution patterns of straight, naturally braided, and artificially straightened reaches under different discharge conditions. [Methods] A high-resolution two-dimensional flow and sediment transport model was established for a typical 8.41 km reach at the Tatilike Village section of the mainstream of the Tarim River. A high-precision initialization method was innovatively adopted. The airborne laser bathymetry was carried out in the dry season (April 1, 2023) to minimize the interference of suspended sediment, and a high-precision digital elevation model with a resolution of 3 m was generated as the initial riverbed topography. One-dimensional and two-dimensional models were coupled, and the validated one-dimensional model provided boundary conditions for the two-dimensional model, including the temporal discharge series at the inlet boundary and the temporal water depth series at the outlet boundary. With integrated spatiotemporal analysis, this model simulated daily morphological changes from April 1, 2023 to November 30, 2023, and output data at 21 characteristic cross-sections, cross-sections in braided reaches, and cross-sections in artificially straightened reaches. [Results] Compared with discharge, sediment concentration, and daily sediment concentration variation, daily discharge variation was the main hydrological factor affecting the intensity of erosion and deposition at the thalweg of channel cross-sections. In different hydrological periods, including the dry season before flood, the medium-water season before flood, the flood season, and the post-flood season, the correlation between daily discharge variation and daily thalweg elevation variation showed an increasing trend, with the strongest correlation in the post-flood season. The erosion and deposition process of the river channel exhibited significant seasonal differentiation. The influence of different periods on the evolution of the main channel followed the order: post-flood season>flood season>medium-water season before flood >dry season before flood. [Conclusion] Daily discharge variation is the main driving factor controlling daily riverbed elevation changes and exhibits clear seasonal characteristics. Their correlation gradually increases from the dry season before flood to the post-flood season and reaches the strongest relationship and maximum net erosion intensity after the flood peak. Given the significant impact of the post-flood season on channel reshaping, management strategies should prioritize monitoring during this period and prepare for possible interventions. The established evolution intensity sequence (post-flood season > flood season > medium-water season before flood>dry season before flood) provides a framework for predicting periods of high geomorphic activity and related ecological impacts, such as habitat gain and loss, and bank slope stability. The differentiated evolution trajectories of braided channels and the intensive erosion-dominated adjustment of artificially straightened reaches indicate that management and restoration measures must be tailored to specific reach types. This study provides a scientific basis for river planning and for responding to water diversion, climate change, or engineering interventions, and will effectively support the sustainable restoration practices of the Tarim River ecosystem.