Sediment Distribution, Depositional Trends, and Their Impact on the Operational Longevity of the Jiahezi Reservoir

The Jiahezi Reservoir is a typical plain reservoir constructed on a sediment-laden river in the mountainous region of Xinjiang. After 58 years of operation, it faces critical challenges—particularly insufficiently characterized sediment size distribution and siltation behavior—that continue to undermine its long-term operational performance. This study investigates particle-size distribution and depositional trends through integrated field sampling and two-dimensional (2D) numerical sediment modeling, using the Jiahezi Reservoir as a case study. Results show that the median particle size (d 50 ) is 0.027 mm, with 76.48% of the particles ranging from 0.005 to 0.25 mm, indicating predominantly fine-grained sediment. Particle size gradually decreases both downstream and laterally from the channel. Hydrodynamic sorting produces distinct spatial distribution patterns, with fine particles occupying more extensive areas than coarse ones. The sedimentation patterns within the reservoir area can be broadly categorized into four distinct zones. By analyzing sediment transport mechanisms and depositional characteristics, this study establishes a foundation for developing targeted strategies to enhance the reservoir’s operational longevity.