Study on the Impacts of River-damming and Climate Change on the Mekong Delta of Vietnam

Abstract

Since the end of 2015, salinity intrusion and drought of different degrees hit the Vietnamese Mekong Delta (VMD). Between March and April 2016, China increased the released outflow discharges from Jinghong Hydropower station to the downstream reach of the Mekong River, following Vietnamese request after the worst drought event over the last 90 years. The released flow may mitigate the drought and high salinity intrusion occurred in several provinces in the VMD. This research aims at summarizing some damages information caused by drought event 2015-2016 and figuring out some possible impacts of six existed and eleven proposed dams in the mainstream Mekong River on the VMD. Water levels in the period of 2012-2015 is about 1m lower and two months shorter than that in period 1993-2001. This leads to salinity concentration increasing about 10-15 g/l in some locations. The timing and duration of salinity levels of the VMD at post-dam periods is shifted about 1 month earlier than pre-dam period. Eleven proposed mainstream dams along with 47 cm sea level rise will lead to a maximum reduction of about 15% and a maximum water level increase of approx. 220% in the VMD.