At the very southern tip of Laos, on a stretch of the Mekong where the river tumbles over falls that reach over sixty feet high, countless channels have formed rough rapids and thousands of islands. This section of the Mekong is too rough for boats, and is the main reason the river is not completely navigable all the way from Vietnam to China. It’s home to catfish that can grow to ten feet long, supposedly the largest freshwater fish in the world. Stand there and look downstream: two kilometers away is Cambodia, beyond that Vietnam and the South China Sea. Look upstream as the river courses for thousands of miles through Laos, along the border with Thailand, to Myanmar and then China and finally to the river’s headwaters high in the Himalayas. One of southeast Asia’s longest rivers, the Mekong is a source of life and livelihood for millions of people who fish its waters and farm its banks. It also has huge hydropower potential, and the falls on the border of Laos and Cambodia are, like the South China Sea, quickly becoming a hot battleground in Asian geopolitics.The dam to be build at the falls is called Don Sahong; a Malaysian company agreed to build the facility several years ago. Not far away another dam will be built by a Chinese company. Cambodia and Vietnam, which both lie downstream from the dams, have asked the Laotians to delay the projects, saying the dams will threaten rice farmers, fishermen, and biodiversity downstream. Laos disagrees and has vowed to push forward with construction almost immediately. The conflict is drawing in China, which will be funding and building at least one of the dams and is a major political and economic ally for Laos. And it’s also of concern to the U.S., which has been pushing for peaceful, cooperative development of the Mekong’s hydropower resources, and is increasingly becoming Vietnam’s ally in its battle against China.China is “a reliable friend,” said the Lao President when the Chinese Defense Minister came to town last month. As Xinhua reported, “Chinese party, government and army have long been providing assistance to Laos, contributing greatly to maintaining Lao national independence and promoting socio-economic development, the [Lao] president said.”Facing off against China and Laos in this intensifying fight are Cambodia and Vietnam and, in the background, the United States. “No one country has a right to deprive another country of the livelihood and the ecosystem and its capacity for life that comes with the river,” Secretary Kerry said in December on a visit to the Mekong delta in Vietnam. The Mekong River is “essential to our socioeconomic development, and regional food security is also at stake,” said Vietnam’s prime minister in April. The G-7, eyeing China’s aggression in the South China Sea, issued a harsh condemnation of Beijing’s actions in Asia’s maritime disputes last night: “We oppose any unilateral attempt by any party to assert its territorial or maritime claims through the use of intimidation, coercion or force.”The South China Sea is where the most intense battle over Asia’s waters, resources, and territory is taking place, but the potential for a new battleground to open on land is growing. Asia’s major rivers are vital for the life and security of entire nations in South and Southeast Asia; China happens to control the headwaters of almost all of them. With dams being built on the Mekong and half a dozen other rivers with the intensity of a horde of beavers, the battle for Asia’s rivers, and thus for control over amazing hydropower potential and other valuable resources, is heating up fast.