Development of Kaoping River Basin Management Strategies Based on Calculated Carrying Capacity

The Kaoping River basin is the largest and the most intensively used river basin in Taiwan. It is 171-km long, 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 relevance legislations 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 (NPS) 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, 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. The calculated daily Escherichia Coliform (E. Coli) loadings to Kaoping River are 1.18×10¹⁶ colony forming unit (CFU). However, the calculated BOD, NH₃-N, and TP carrying capacities are only 27,700, 4,200, and 600 kg per day. The calculated E. Coli carrying capacity is only 4.81×10¹⁵ CFU per day. Thus, the current BOD, NH₃-N, TP, and E. Coli loadings are almost 2.7, 9.4, 8.5, and 7.3 times higher than the calculated carrying capacities, respectively. To protect public health and improve the river water quality, the comprehensive management and construction strategies are proposed. The proposed strategies include the following measures to meet the calculated river carrying capacity. (1) 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 significantly reduced.