A study of thresholds of runoff and sediment for the land accretion of the Yellow River Delta
A study of thresholds of runoff and sediment for the land accretion of the Yellow River Delta
复制标题
作者：
Xu Jiong
黄河是世界上著名的多沙河流，其淤积过程对降水变化和人类活动等影响因素十分敏感。因此，黄河三角洲是研究陆-海相互作用下三角洲发育的理想场所。黄河三角洲的发育是河流与海洋动力相互作用的结果，也是河流与潮汐输送物质通量相互作用的结果。陆地增生的速度受这些相互作用的控制。当这两方面处于平衡状态时，三角洲的冲淤过程可考虑在临界条件下进行，河流补给的水沙量可作为冲淤的水沙阈值。通过不同时期的海图与遥感图像的对比，得出了该地区的年增陆面积。为了确定黄河三角洲发育的水沙阈值，根据1955 - 1989年黄河三角洲的资料，建立了黄河三角洲的淤积速率与入河口水沙量之间的回归方程。根据这些关系，估算出黄河三角洲的泥沙淤积阈值为2.78 × 108 t，径流淤积阈值为76.7 × 108 m3，在此水沙条件下，黄河三角洲处于平均平衡状态。如果年输沙量小于2.78 × 108 t，年径流量小于76.7 × 108 m3，则三角洲可能发生侵蚀，土地流失，从而严重影响三角洲的环境安全。为了更好地管理黄河环境，这些阈值应作为约束条件之一。黄河生态需水量的含义应扩大，以包括维持三角洲土地增长平衡所需的水量。
The Yellow River is the most famous heavily sediment laden river of the world, its land accretion process is sensitive to influencing factors such as the changing precipitation and human activities. Thus, the Yellow River Delta provides an ideal site to study the delta development under the land ocean interactions. The development of Yellow River Delta can be regarded as the outcome of interactions between the river and marine dynamics and of interactions between the river and tide transported material fluxes. The rate of land accretion is controlled by these interactions. When the above two aspects are in equilibrium, the land accretion process of delta may be thought under the critical conditions, and the river supplied water and sediment quantities may be considered as thresholds of runoff and sediment for land accretion. By comparison between the sea charts and remotely sensed images made in different periods, the annual area of land accretion has been obtained. To identify the water and sediment thresholds for delta development, two regression equations have been established between land accretion rate and water and sediment quantities into the river mouth, based on the data from the Yellow River Delta in the period of 1955 1989. From these relationships, the threshold of river supplied sediment quantity for land accretion has been estimated as 2.78 10 8 t, and the threshold of runoff as 76.7 10 8 m 3 ; under these sediment and water supplies, the Yellow River Delta may be in equilibrium in an average sense. In other words, if the annual sediment quantity is less than 2.78 10 8 t, and the annual runoff less than 76.7 10 8 m 3 , the delta might be eroded and the land would be lost, and thus the environmental security of the delta might be seriously affected. For a better management of the environment of the Yellow River, these thresholds should be taken as one of the constraints. The meaning of ecologically needed water use in the Yellow River should be extended, in order to include the water quantity that is required for maintaining the balance of land accretion in the delta.