A Pulsing River

Part of the Water: H2O = Life exhibition.

Tonle Sap fishing
© Gavriel Jecan / AGE Fotostock

Imagine a rainstorm that lasts for months each year, dumping so much water into a river that one of its tributaries starts flowing backward. This happens each year when the monsoon rains hit Southeast Asia. A tributary of the Mekong River switches directions, sending a flood of water into Cambodia's Great Lake, or Tonle Sap, which swells to six times its previous size.

Tonle Sap River
© AMNH / Denis Finnin

Rather than devastating the region, the flood brings life to the lake. Millions of fish, from tiny carp to humongous catfish, surge into the lake along with the floodwaters. For most of the 80,000 people living around the lake, these fish are the key to their livelihood. The rising and falling waters influence nearly everything about life here--houses and entire villages are built on stilts, for instance, or float on pontoons.