Sediment Movement

Sediment Movement Image

Sediment can move in a water body as suspended in the water column or the bottom...

    Sediments provide part of the “lifeblood” of a river, transporting materials eroded from upstream to down, carrying with them nutrients and carbon. How sediments are distributed greatly effects in stream and downstream landforms, including the Delta in Viet Nam. The sediment transport capacity is the ability of the river to suspend and carry sediments from zone of production to zone of deposition. As the capacity changes, so does the amount of sediment load carried. As the Mekong Basin was formed by different tectonic shifts millions of years apart, there are differing sediment yields for different areas of the basin. The Ailao-Shan shear zone and the Central Highlands dominate sediment production, with smaller sediment contribution from northern Lao tributaries. The discharge of the river into the ocean provides nutrients critical to support production for coastal fisheries.

     The current sediment load is on the order ~100-150 x10⁶m³/yr. The critical question is, what will happen to future sediment yield under different dam development scenarios?

The challenges of understanding the transport of sediemnt is summarized by Wang et al (2011).....“Although sediment issues have critical implications for aquatic ecology, agriculture, water supply and river navigation, studies regarding the sediment production, deposition and transportation in the Lower Mekong River are relatively sparse. With the construction and operation of dams in the Upper Mekong River, this issue has attracted considerable attention in recent years. The estimation of sediment loads has been hindered by the serious lack of sediment measurements in the Lower Mekong River. Wang et al (2011) investigated the possibility of estimating the sediment loads for the years without good quality measurements in the Lower Mekong River. To make this estimate, the study classified the rating curves on the basis of the synchronous nature of the suspended sediment concentration and the water discharge among the adjacent stations (e.g. Chiang Saen, Luang Prabang, Nong Khai, Mukdahan and Khong Chiam). Together with other methods, it was possible to estimate the yearly sediment loads for the period of 1962–2003 at the five mainstream Lower Mekong River stations. Consequently, the spatial and temporal variations in the sediment loads and water discharge in the Lower Mekong River were examined. In addition, the possible impacts of Chinese dams as well as the annual sediment load of the Mekong River into the sea were also investigated.”

Wang, J.J.,m X.X. Lu, and M. Kummu. 2011. Sediment load estimates and variations in the lower Mekong River. River Res. Applica. 27: 33-46.