Water quality management in the Kaoping River watershed, Taiwan

The Kaoping River basin is the largest and the most intensively used river basin in Taiwan. It is 171 km long and drains a catchment of more than 3,250 km2. Based on the current water quality analysis, the Kaoping River is heavily polluted. Concern about the deteriorating condition of the river led the Government of Taiwan to amend the relevant legislation and strengthen the enforcement of the discharge regulations to effectively manage the river and control the pollution. Investigation results demonstrate that both point and non-point source pollutants are now the causes of biochemical oxygen demand (BOD), nutrients, and pathogens in the river. The main water pollution sources are livestock wastewater from hog farms, municipal wastewater, industrial wastewater, non-point source (NPS) pollutants from agricultural areas, and leachate from riverbank landfills. The current daily BOD, NH3-N, and TP loadings to Kaoping River are 74,700, 39,400, and 5,100 kg, respectively. However, the calculated BOD, NH3-N, and TP carrying capacities are 27,700, 4,200, and 600 kg per day. To protect public health and improve the river water quality, a comprehensive management and construction strategy is proposed. The proposed strategy includes the following measures to meet the calculated river carrying capacity: (1) a hog ban in the entire Kaoping River basin, (2) sewer system construction to achieve 30% of connection in the basin within 10 years, (3) removal of 10 riverbank landfills, and (4) enforcement of the industrial wastewater discharge standards. After the implementation of the proposed measures, the water quality should be significantly improved and the BOD and nutrient loadings can be reduced to below the calculated carrying capacities.