BANGKOK — SITTING in his small grocery built on stilts over a canal, Tong Koo Pua scoffs at warnings that Bangkok's waterways are imperiled. ``My family has lived here for 100 years,'' he says. ``The river isn't dirty. I take a bath in it every day.''
For centuries, the Chao Phya River and its Venetian network of canals have been a centerpiece of Thai life. Now, fast-paced urban growth and widespread abuse threaten to choke Thailand's most venerable waterway.
``Everyone over the age of 35 remembers the good old days on the Chao Phya River,'' says Chodchoy Sophonpanich, a businesswoman and member of a prominent Bangkok family. ``The waterways were accepted as the place where you did everything: You swam in it, you lived on it, and you took the water for granted.
``All of a sudden, the population, industry, and economy have increased dramatically, and we are being swamped with problems,'' says the woman who heads an effort to clean up the river. ``If something isn't done, the Chao Phya will soon be dead.''
Already, scientists and environmentalists say, water pollution has reached such horrifying proportions that many of the canals, known as klongs, are putrid, overgrown with plants, and aquatically extinct.
Parts of the river, which flows about 185 miles to the Gulf of Thailand and is the region's Mississippi River, are almost totally deprived of oxygen by organic pollutants, which need oxygen to decompose, and certain species of fish have disappeared.
Bangkok, a city with 6 million people and no sewerage system, uses the Chao Phya and the canals as a dumping ground for untreated waste from households and many businesses. Industries that do treat waste have inefficient systems or often fail to use them.
For three decades, Bangkok has debated the construction of a sewer system, although the project has repeatedly snagged on political bickering and resistance from business, industry, and residents to paying fees for waste treatment.
A river cleanup has been stalled by a bureaucratic tangle involving a gaggle of government agencies with responsibility for water quality.
Officials of the Bangkok Metropolitan administration, which is in charge of cleaning up the klongs, say they want to push ahead with plans for an $800 million waste-treatment plant. A stack of studies on proposed waste-treatment systems for Bangkok already are gathering dust.
Other experts propose a more modest beginning. A research team at the Thailand Development Research Institute suggests a network of pipes to intercept waste water along the canals and carry it to eight plants around the city for treatment.
Environmental activists and water-quality experts say Bangkok's fading waterways - the country's traditional boulevards and byways - remain central to Thai life and the economy and must be saved.
The institute estimates that Thailand could reap economic benefits of $50 million yearly from cost savings in treating the water supply, increased production stemming from the lower cost of using clean water, and appreciation of land values, as well as improvements in public health.
Although many canals have been covered over, many Thais still live a traditional waterborne life along tranquil klongs not far from the traffic- and pollution-choked city center.
Old houseboats drift among orchid farms and durian fruit plantations. Small vendors carry on a lively commerce, sculling among clusters of stilt houses that line many canals. River taxis and fast-moving long-tail boats skim passengers and cargo along the waterways.
``The Chao Phya is more than just a river,'' says a report by the research institute. ``It is a symbol of the nation.''
Ms. Chodchoy, whose Thai Environmental and Community Development Association is the country's only private environmental lobby, says Thais are much more conscious of environmental issues now than they were when she started her organization in 1983.
A former advertising and marketing executive, Chodchoy launched the association as an antilittering campaign, prodded by concern about her own children's littering habits. She is now targeting the parallel river-cleanup campaign to young people and students and hopes to place individual waste-treatment systems in Bangkok homes and restaurants, the two biggest polluters of the waterways.
But old habits die hard, says the activist. She has gotten little response from Thailand's tourist industry, which faces a major threat from environmental degradation. ``They should be the first to become involved, and they are the last,'' Chodchoy says.
Establishing a civic sense in Thailand also is an uphill battle.
``This is something we don't teach in Thai society. We teach children how to behave toward elders and keep yourself and your house clean,'' she says. ``But we're not taught to look after public areas as part of our responsibility.
``When the country develops to a certain point, then people start thinking about civic responsibility.''