Satellite Flood Comparison Tonle Sap 2009-10

I have finally managed to track down Tonle Sap satellite images to compare last year’s low levels with a normal year. These images were taken at the peaks in 2009 (a fairly average year) and 2010. It makes worrying viewing. Interestingly 1998 is the lowest on record (only slightly lower than 2009) and 2000 is the record high. The lake also reached its peak some 6-7 weeks later than normal. (cont below)

Tonle Sap Early Oct 2009, an average year

Tonle Sap Late Sept 2010

The effect of this was that fish were unable to reach their normal breeding grounds around the lake, which failed to flood. Many fishermen reported catching pregnant fish and the government’s annual test for fish spawn was almost 60% lower than normal.

Hyrdo dam reservoir in Southern Laos May 2010

As this year’s weather patterns seem to be similar to last years this could happen again. I do wonder what the knock on effects would be on already under pressure fish stocks, not to mention the lack of siltation will have on rice farming around the lake? The Vietnamese must be worried too, as last year many farmers were unable to grow rice due to the increased salinity of the water on the delta. This is because in a normal year the shear volume of water reaching the delta pushes the sea water back allowing farmers to grow a wider ranger of crops.

Why did this happen? Reduced rainfall is certainly partly to blame, however, having visited several reservoirs in Laos and northern Thailand last year and seen just how low they were, it is clear they also played a big part. They would have taken several weeks to fill before any excess would have been allowed to flow through to the Mekong.

Hyrdo dam reservoir in Southern Laos May 2010

Hyrdo dam reservoir in Southern Laos May 2010

With around 60 more dams planned for tributaries in the lower Mekong region, the Tonle Sap and the millions who rely on its normally abundant resources, look to be under great threat.


About Allan Michaud

English Wildlife Photographer/Environmental Filmmaker based in Cambodia
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