Shortly before sunset one recent evening, Nakorn Jittangkul, a 47-year-old Thai villager, was crouched in his small vegetable garden near the Mekong River, replanting coriander that had been washed away by a surge of river water a few days earlier.

Mr Nakorn, who has lived his entire life in Chiang Kong on the banks of the river, complained that the once predictable Mekong had become volatile – with unusual surges and drops of the water levels and declining fish stocks – developments he blamed on several hydropower dams built by China far upstream.