The Mekong is the 12th longest river in the world with the 8th greatest volume of water, and in terms of biodiversity is exceeded only by the Amazon. More than 1,200 species of fish alone have been identified, many of them unique to the river and adapted to its particular conditions.
Each year between June and November the river floods, to such an extent that the Tonle Sap river, the tributary which connects the Mekong and the great Tonle Sap Lake at the Cambodian capital Phnom Penh, reverses its flow. The river literally runs uphill, such is the force of the floodwater, and the lake itself expands fivefold. This flooding creates ideal spawning grounds for fish - there are accounts from last century of fishermen having difficulty in navigating the lake because the sheer volume of fish impeded their oars. Even today traditional fishery and fish farms are estimated to produce around 2M tonnes of fish each year.
The floods are also vital for agriculture, in particular rice cultivation which supplies the other staple foodstuff for most of the inhabitants of the Mekong Basin. The Mekong Delta area, fertilized by rich silts brought down by the floods, provides 40% of Vietnam's total rice production.
But excessive and uncontrolled flooding results in ruined crops, the destruction of housing and loss of life.
In 2000 particularly bad floods caused an estimated $500M of damage, 795 people lost their lives, half a million Cambodians and many hundreds of thousands Vietnamese were made homeless, and damage to the Vietnamese rice crop was estimated at $20M.
For many of the inhabitants of the Mekong Basin the river is their source of life. Food and water come directly from the river, and any extra income is likely to be derived from river-based activities such as fishing or rice cultivation.
It provides water for drinking, cooking and washing their clothes. Their houses are built on stilts to ride above the floods or they live in roughly constructed houseboats on the river itself.
Average annual per capita income for people living in rural areas along the river is between US$200 and $400. Despite the outstanding natural beauty of the area in which they live, these are some of world's poorest people.