Swindling the Mekong: Run-of-River Hydro

Saturday, March 31, 2018
Swindling the Mekong: Run-of-River Hydro

Many of the existing and planned hydropower dams in the Lower Mekong Basin are referred to as ‘run-of-river’ projects. This includes the 11 hydropower dams that are planned and under construction on the Lower Mekong mainstream. Run-of-river hydropower schemes have become popular among dam proponents as a supposedly “low-impact” alternative to large reservoir and traditional storage dams. However, rather than serving as a low-impact alternative, run-of-river dams often have serious and long-lasting impacts, particularly on downstream ecosystems. These impacts have tended to be overlooked and understudied because of the widespread assumption that such projects are benign, aided by a lack of any meaningful definition of the term.

The term "run-of-river" is sometimes used by dam proponents and developers to describe dams in the Lower Mekong Basin in the context of providing assurances that a hydropower project’s impacts will not be significant or can be minimized. 
But what is a "run-of-river" hydropower project? And does "run-of-river" mean that dams in the Mekong Basin will have limited impacts, or that their impacts can be effectively mitigated?

This fact sheet discusses the term "run-of-river" (ROR) as it is applied to different types of hydropower projects. While there is no single definition, ROR is generally applied to hydropower projects that have limited water storage capacity. Despite differences from traditional reservoir and storage dams, ROR projects can have severe impacts on ecosystems and aquatic species. Some of these impacts are inherent to a dam project; others depend on how it is operated.

The dams that are planned and under construction on the Lower Mekong mainstream and many of the dams within the basin are classified as ROR projects. However, the storage capacities, reservoir sizes and operational strategies of each of these projects differ greatly. Some of the Mekong mainstream dams have the capacity to retain flows for extended periods of time, and some have very large reservoirs, submerging large areas of land and displacing thousands of people.

The factsheet examines case studies of projects in the Mekong River basin that are classified ROR and their impacts, including the Pak Mun Dam, Xayaburi Dam, Don Sahong Dam and the Pak Beng Dam.

Read the "Swindling the Mekong: Run-of-River Hydro" fact sheet in English, Thai, Khmer or Vietnamese.