Mekong at the crossroads: next steps for impact assessment of large dams.

The Mekong River in Southeast Asia stands at the crossroads. As discussed in Ambio Special Issue (Kummu et al. 2008), the crossroads is ultimately about the way the river and its abundant resources should be used, with the most heated debate evolving around the issue of large hydropower dams. A relatively pristine river with an estimated hydropower potential of 53000MW in the basin, the Mekong forms a tempting source of energy for the growing riparian economies (ICEM 2010; Grumbine and Xu 2011). Yet, the dams are estimated to radically reduce the current benefits derived from the river, including its multibillion dollar fisheries that form the basis for food security and livelihoods for millions of people (Kummu and Sarkkula 2008; Lamberts and Koponen 2008; Dugan et al. 2010; Arthur and Friend 2011). The thematic crossroads thus appears largely as a choice between large-scale, economicdriven water utilization and a more diverse, decentralized use of water-related resources (Keskinen 2008; Kummu et al. 2008; Molle et al. 2009; Lazarus et al. 2011; Stone 2011). We argue that there is also another, methodological crossroads that deals with the most suitable ways to assess the development plans. While this crossroads is much less discussed, the entire debate about the Mekong development revolves very much around such assessments, as their findings are used to justify the development plans. The contradictions regarding the assessments became well visible last April, when the four member countries of the regional Mekong River Commission (MRC) failed to reach a consensus on the first mainstream dam proposed by a MRC member country, namely the Xayaburi dam in Laos (MRC 2011a). Laos insists that the planning of the project is sound and the dam construction can start, followed by a number of other mainstream dams. Other MRC countries of Cambodia, Thailand, and Vietnam are, however, concerned about harmful impacts, and call for more rigorous assessments—Vietnam even suggested a 10-year suspension of all mainstream dam plans to allow enough time for this. As a result, during the MRC Council Meeting in December 2011, the ministers from the four MRC countries agreed that a further study about the impacts of the mainstream hydropower projects is needed (MRC 2011b). The suggested strengthening of the regional assessment processes has a good chance to become a landmark event even beyond the Mekong, and it can make the Mekong countries the forerunners in cumulative assessment of hydropower dams and other large-scale water development. For after a slowdown in the construction of large dams at the turn of the millennium due to their remarkable environmental and social costs (WCD 2000), recent years have witnessed a renewed interest toward hydropower (Moore et al. 2010). This has been partly thanks to improved planning and assessment processes, but first and foremost due to rapidly increasing energy demand particularly in the developing world. In the Mekong, the combination of high dependency on hydrocarbons and rapid increase in electricity demand—around 8% per year, one of the highest in the world—has led to a renewed push toward large-scale hydropower (ICEM 2010). Well over hundred large dams are planned to the mainstream and the tributaries (MRC 2010; Fig.1), making the Mekong the