Flowing from the headwaters in Tibet, the Salween traverses China and Myanmar and defines part of Thailand’s western border. Stretching over 3,200km (2,000 miles), it is Asia’s longest free-flowing river, running from the Three Parallel Rivers of Yunnan province in south-west China to the delta near Mawlamyine in south-east Myanmar, where it meets the Andaman Sea. However, plans for seven major hydropower projects along the Salween basin threaten this status.