It has been a bad year for the Mekong. An unusually long period of drought has brought water levels to some of the lowest measurements in recent years.
There are fears that the drought will have a particularly negative effect on the Tonle Sap River, connecting the Mekong to Cambodia’s Great Lake and which plays a key role in the maturing of the fish stocks on which population of the Lower Mekong Basin depends. If its normal flood pulse is sharply reduced, minimising the flow of the tributary backwards to the lake, there will be serious negative effects.
Upstream from Cambodia, in Laos there have been complaints about declining fish stocks due to the drought. These were compounded by unannounced water releases from China’s Jinghong dam in southern Yunnan in early July that flooded paddy fields in both Laos and Thailand. (A recent National Geographic feature details the challenge.)
In full: http://lowyinstitute.org/the-interpreter/mekong-when-river-runs-dry