长江流域泥沙输移与概算

Sediment budget of the Yangtze River

泥沙概算是一种通过研究泥沙在流域不同位置和一定时期内的时空分布,从而揭示河流水沙平衡状态的方法。本文通过分析提出了长江泥沙概算方法,探讨长江流域产沙、输沙和泥沙沉积三者的关系。在此基础上,通过流域侵蚀、沉积物和悬移质泥沙粒径级配的对比分析,计算得出每年从长江上游侵蚀下来的泥沙中,粒径大于0.5mm的近12亿t泥沙几乎都沉积在长江流域上游的沟谷和支流中,粒径在0.05-0.5mm范围内的4.92亿t泥沙有3.13亿t沉积在上游沟谷和支流中,而粒径小于0.05mm的5.36亿t泥沙也有2.02亿t沉积在这些区域。当长江上游(宜昌站)和汉江总输沙量超过2.86亿t时,长江中下游将发生淤积,总输沙量超过5亿t时的淤积量超过1亿t;当宜昌输沙量超过1亿t时,洞庭湖区将发生淤积。文章还根据长江干流、部分支流和通江湖泊的水沙关系,建立水沙动态图,研究分析了长江水沙在时空上的分布特点。

The sediment budget is a method to study the spacial and temporal distribution of sediment in different parts in the river basin and a certain period to reveal the balances of sediment and water in the river. In this paper, the authors present a sediment budget method of the Yangtze River and qualify the relationship among the various components of the overall drainage basin sediment erosion-transportation-deposition system. The size distributions of eroded sediment, deposit and suspended sediment in the basin are analyzed. The results show that almost all the 1.2 billion tons of sediment coarser than 0.5 mm eroded from the watershed deposits in the gullies and tributaries of the upper Yangtze River basin, 313 of the 492 million tons of sediment of diameter in the range of 0.05 - 0.5 mm and 202 of the 536 million tons of sediment finer than 0.05 mm also deposit in the said region. If the total incoming sediment load from the upper Yangtze River and Hanjiang River is more than 286 million tons, sedimentation occurs in the river. If the value is around 500 million tons, 100 million tons of the sediment will deposit in the river. In addition, if the sediment load of Yichang exceeds 100 million tons, sedimentation also occurs in the Dongting Lake. Moreover, according to the relationship between the total sediment load and water discharge of the Yangtze River, its some tributaries and riparian lakes, their water-sediment diagrams are set up to analyze the spatial and te distribution of sediment and water and their variation processes.