The Mekong Basin has an area of 795,000 km2. The upper basin section in China and Myanmar makes up 24 per cent of this area and contributes approximately 18 per cent of total flows (MRC, 2005a). The LMB includes the upland areas, including the tributaries that drain the highlands of Lao PDR, the Nam Mae Kok watershed in Thailand and the Se Khon-Se San-Sre Pok (Three S) watershed shared by Cambodia, Lao PDR and Viet Nam. Together, these upland areas, which are fertile, forested and have high rainfall, contribute approximately 65 per cent of total flows.