Thailand State of Environment Report 1997 1995-1996 1997 4. Pollution 4.1 Water Pollution Status In 1997 the Pollution Control Department undertook a water quality survey of the country and found 14 percent of water resources are in good condition, i.e suitable for aquatic animals and general human consumption. These are Kwai Noi River, Siew River, Kwai Yai River, Langsoan River