Tonle Sap Lake

This huge lake (about the size of Cheshire) lies to the south of Siem Reap in NW Cambodia, and is a phenomenon.  

The e in Tonle has an acute accent, which is not available in this blog's HTML. Apologies all.

The lake is, in a sense, tidal - the tide comes in once a year. When the Mekong (the world's 12 largest river, pub quiz goers) is in spate, all the meltwater and rains that swell it from its origins in the Tibetan plateau cause the water level to rise higher than Tonle Sap. This causes Tonle Sap river, which meets the Mekong in Phnom Penh, to flow backwards and fill the lake from about July to Sept (which, coincidentally, is also the wet season). At this time, all the surrounding shore, including many paddy fields, floods over. Villages would also flood over, were they not built on stilts or floating on the lake itself. 

Fishing goes on almost year-round, and there are many  wetland birds unique to the area.

Tonle Sap lake. Thanks NASA for the pic. You guys don't need any cash from me, but let me know if you're thinking of legal action.

What this meant for Angkor

The massive irrigation system that supported Angkor Thom and the other sites in the Angkor area, with their enormous reservoirs and intricate hydraulic systems, depended on the annual cycle of rising waters. It may very well be that the sites were abandoned because of a failure in the annual replenishment of Tonle Sap, leading to a failure in the rice harvest.

Nobody seems to have proposed the opposite theory, that the area may have flooded for an unduly long period. We will probably never know the truth.