Development of Watershed Management Strategies for the Chiang-Chun River Basin, Taiwan

The Chiang-Chun River basin is the largest and the most intensively used river basin in Tainan County, Taiwan. Based on the recent water quality analysis, the Chiang-Chun 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 show that the hog farming is one particularly important activity in the watershed. Most of the untreated hog farm waste is indiscriminately discharged into the river. Moreover, municipal wastewater in the watershed is also discharged into the river without proper treatment. Thus, the hog farm and municipal wastewaters are the major causes of the deterioration of water quality of Chiang-Chun River. Currently, the percent of sewer system connection in the Chiang-Chun River watershed is less than 1%. Investigation results show that the daily wastewater, biochemical oxygen demand (BOD), and ${\mathrm{NH}}_3\text{-}\mathrm{N}$ loadings into the river are approximately $\mathrm{101,600}{\mathrm{m}}^3$ , $\mathrm{15,800}\mathrm{kg}$ , and $\mathrm{3,900}\mathrm{kg}$ , respectively. Results also indicate that the domestic wastewater and hog farm waste contribute more than 50% of the daily BOD and ${\mathrm{NH}}_3\text{-}\mathrm{N}$ loads to the river, respectively. In this study, the enhanced stream water quality model was selected as a water quality-planning tool to perform the water quality evaluation and carrying capacity calculation. The calculated BOD and ${\mathrm{NH}}_3\text{-}\mathrm{N}$ carrying capacities were 2,700 and $210\mathrm{kg}$ per day, respectively. A comprehensive strategy for the management of Chiang-Chun River basin has been proposed based on the results from water quality investigation and modeling. The strategy consists of short-term management and improvement measures, long-term structural measures (e.g., sewer system construction to achieve 30% of connection in the basin within 10 years), and land use management and legislation (e.g., river bank management and enforcement of wastewater discharge standards). After the implementation of the proposed measures, the water quality can be significantly improved. The developed watershed management strategies can also be applied to other similar watersheds.