River, lakes and other water bodies are polluted mainly due to concentrated discharge of industrial wastewater and sewage. Such a large amount of wastewater exceeds the carrying capacity of a water body (meaning that the river takes in too much polluted water). To reduce water pollution in water bodies, the Environmental Protection Administration (EPA) adopted total quantity control method for sections of rivers that were more heavily polluted. The amount of polluted water that can be released to the section everyday is based on the carrying capacity of the water body.

According to Article 9 of the Water Pollution Control Act, the EPA shall implement controls using total quantity control methods for the discharge of wastewater or sewage by following the 5 principles illustrated in the figure below. Impaired water bodies should be first identified, and control methods should be adopted for the discharge of pollutants.