Like many countries in Asia, increasing population, economical, agricultural and industrial expansion in Thailand are the major causes of water quality in various water sources, including surface water, ground water and sea water to be deteriorated. High loading of pollutants from human activities beyond the water resource carrying capacity can contribute to degradation of water quality in the country.
In general, the water quality of water resources in Thailand is in fair condition with a significant trend of improvement. However, the surface water quality of major rivers, lower Chao Praya, Tha Chin, Lam Takhong and Songkhla Lake, particularly in the areas where receiving pollutants discharged from industrial, agricultural or populated areas. Similarly, the coastal water in the Inner Gulf and certain highly populated areas of the Outer Gulf of Thailand are in poor quality, particularly in the areas into which four main rivers flowing (Mae Klong, Tha Chin, Chao Phraya and Bang Pakong Rivers). Despite the currently good condition of the coastal water quality, high levels of significant pollutants are closely monitored in many densely-populated and/or tourist areas of the Andaman Sea.