Model-based assessment of water, food and energy trade-offs in a cascade of multi-purpose reservoirs A case study from the Sesan tributary of the Mekong River

The Mekong River Basin in Southeast Asia is undergoing rapid development in the exploitation of its water resources. Although hydropower is the most dominant driver for water development, the possibilities for multipurpose reservoirs have been increasingly discussed but not well studied. The authors assess the potential benefits and negative impacts of a multipurpose reservoir cascade facilitating hydropower and irrigation in the Sesan River, a transboundary tributary of the Mekong. A model-based assessment approach was developed where the hydropower operations of a cascade of reservoirs were simulated together with the irrigation water withdrawals. The assessment revealed that the reservoirs created considerable irrigation potential (28,348 ha), and the resulting losses for hydropower generation were relatively small (-1.6%). The river flow impacts were significant, but they originated mainly from the hydropower operations. The inclusion of irrigation led to an increased competition of water resources during the dry season. In addition, the assessed hydropower and irrigation development affected negatively protected areas, agriculturally valuable land, and forest cover. Gaps and shortcomings in the model-based assessments of water resources development were further recognized, including this one, concluding that particularly the connection to ecological and social domains remains often weak and needs, therefore, to be strengthened. © 2014 American Society of Civil Engineers.