The main cause of deteriorated water quality, according to the PCD, is untreated municipal wastewater
being drained directly into public waterways. In fact, 90% of all wastewater nationwide, including
residential sewage and industrial discharge, flows directly into public waterways untreated according to the
Report. Commercial and industrial expansion, combined with exponential population growth and a rural
migration to Bangkok, has resulted in an accumulation of water pollution that has overwhelmed nature,
leaving it unable to cope. Although the state of Bangkok’s waterways is better than when most of the
environmental legislation was first introduced, their quality still falls well short of what is appropriate for
the great city through which they run.