The Mekong is a trans-boundary river in Southeast Asia, the world's 12th longest river. From the Tibetan Plateau, it runs through China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. The extreme seasonal variations in flow and the presence of rapids and waterfalls make navigation difficult. However, the Mekong is a biological giant, second only to the Amazon in terms of freshwater biodiversity. It is home to the giant freshwater stingray and the Mekong giant catfish. The Mekong Delta in Vietnam is one of the most productive agricultural regions in the world, often called 'Vietnam's rice bowl.' The river's health is currently a major geopolitical issue due to the construction of several large hydroelectric dams that affect sediment flow and fish migration downstream.