Known as the Lancang River in China, the Mekong river is the heart of Southeast Asian countries, with over 60 million people depending on the river and its tributaries for food, water, transport and many other aspects of their everyday routine.
Since 1993, China has installed six dams along the Upper Mekong Basin with a navigation channel that threatens this complex ecosystem. Over 20 more are under construction and being planned in Yunnan, Tibet and Qinghai.
Experts say this will ultimately disrupt the river’s natural flood-drought cycle, and block the transport of sediment, affecting ecosystems and the livelihoods of millions living downstream in Burma, Thailand, Laos, Cambodia and Vietnam. Impacts to water levels and fisheries have already been recorded along the Thai-Lao border.
Despite this, construction has proceeded without consultation with the Lower Mekong Basin communities and without an assessment of the dams’ likely impacts on the river and its people.
However, though studies have not been concluded, the Mekong River Commission’s (MRC) river monitoring arm has indicated that these Chinese dams do affect water flow in the Lower Mekong Basin, specifically by reducing water flow during the wet season and increasing it during the dry season.
Studies have shown that the downstream water flow in the dry season has increased, therefore easing the effects of droughts. Storage dams can contribute to increased flow during the dry season as they discharge water for energy production.
As a result, the release of supplemental water from the Lancang dams eased the regional drought of 2016.
A total of 12.65 billion cubic meters of water was discharged from the Jinghong hydropower reservoir during March to May, 2016. The amount released equaled to 40 – 89 percent of flow along various sections of the Mekong River.
The emergency supplemental water increased water level or discharge along the Mekong mainstream to an extent of 0.18-1.53m or 602-1,010m3/s.
Flows would have been 47 percent lower at Jinghong, 44 percent lower at Chiang Saen, 38 percent lower at Nong Khai and 22 percent lower at Stung Treng if these releases didn’t happen. This additional flow has also alleviated salinity intrusion in the Mekong Delta.
So while Mekong communities should be anxious about the adverse effects of Chinese dams on issues such as sediments and fisheries, these dams have not been proven to reduce downstream flows during the dry season.