By the time the Mekong reaches Vietnam, it has travelled from its source high in the Tibetan Plateau, through China, skirted Burma, flowed along the Laos-Thai border and cut through Cambodia. Nine tributaries of the Mekong criss cross this fertile plain and supply the delta with alluvial rich sediment. Known as the Rice Bowl of Asia, the delta provides about 40 percent of the country's annual food crop. Life in Vietnam’s agrarian heartland continues as it has for centuries; conical-hatted farmers cultivate paddy fields, tend to their tropical orchards, trade produce at the floating markets and fish in the rivers and canals.