5.3 Implications for the Lower Mekong River
Our quantification of sediment fluxes from Ming Yong glacial catchment provides baseline measurements to better understand changes in erosion rates within the context of wider climatic alterations (Li et al., 2021). As the Ming Yong glacial region is part of the upper reach of the Mekong River and Salween River, our study also provides insights into the contribution of sediment to the upper reaches of these transboundary rivers under the fast pace of temperature increase (Figure 2c). For the Mekong Basin, better understanding of sediment supply and delivery in its entire reach is needed for better management of its sediment fluxes. One major issue is the potential impacts of Chinese dams in the Mekong River. Before Manwan Dam was constructed in 1992, the upper Mekong reach in China provided around 80 million tons of sediment to the lower reach (Lu and Siew, 2006; Wang et al., 2011; Lu et al., 2015). However, the high sediment supply from the proglacial catchments in the headwater region cannot be transported downstream because of the series of cascade dams constructed in the Upper Mekong River. According to Sun et al. (2022), the sediment load below these cascade dams in Yunnan has dropped to around 10% of the pre-dam level. Subsequently, the problem of sediment starvation due to the reservoirs trapping will get worse in future with more dams being planned or built. Further down the Mekong Basin, this declining sediment flux, in combination with regional sand-mining and water withdrawal for irrigations, has contributed to drastic water level reductions in the Cambodian floodplains and Vietnamese delta (Lu and Chua, 2021; Chua et al., 2022).