The severe drought now ravaging Southeast and South Asia has helped spotlight China's emergence as the upstream water controller in Asia through a globally unparalleled hydro-engineering infrastructure centered on damming rivers. Indeed, Beijing itself has highlighted its water hegemony over downstream countries by releasing some dammed water for drought-hit nations in the lower Mekong River basin.

In releasing what it called "emergency water flows" to downstream states over several weeks from one of its six giant dams — located just before the Mekong flows out of Chinese territory — China brashly touted the utility of its upstream structures in fighting droughts and floods.

But for the downriver countries, the water release was a jarring reminder of not just China's newfound power to control the flow of a life-sustaining resource, but also of their own reliance on Beijing's goodwill and charity. With a further 14 dams being built or planned by China on the Mekong, this dependence on Chinese goodwill is set to deepen — at some cost to their strategic leeway and environmental security.