This map shows the status of more than 200 dams (larger than 15MW) planned, under construction or completed in the Lower Mekong basin portions of Thailand, Vietnam, Cambodia, and Laos. Already more than 100 are completed on the Mekong tributaries and 2 on the Mekong Mainstream in Laos (Xayaburi Dam and Don Sahong Dam). Dams are built for different purposes in these countries, but each dam delivers impacts to the mighty Mekong’s ecological processes and natural resources upon which tens of millions depend. Dams cut off migratory pathways for fish – the Mekong produces 20% of the world’s freshwater fish catch. Dams also currently block more than 50% of the Mekong’s sediment load and that sediment is necessary for the fish population and agricultural processes, particularly in Cambodia and Vietnam. To illustrate, the Mekong Delta in Vietnam produces more than 50% of Vietnam’s rice export and 70% of Vietnam’s fruit and fish export. Natural floods used to send that sediment across the Mekong Delta but upstream dams are severely reducing the ability of those floods to provide freshwater to the Mekong Delta. Importantly more than 250 small hydropower dams in Laos (less than 15MW) are not shown on this map.