In order to improve water quality and establish sustainable water environment, the Department of Environment Protect of the Taipei City Government has carried out various plans of water quality improvement for the Danshuei River. The purpose of this project is to collect the monitoring data of the Danshuei River, including water quality and flow, and to propose water quality index and present water quality improvement strategies for impaired segment of the Danshuei River. In order to achieve the goal, the tasks of this project include :(1) analyzing the data of water quality collected from the Danshuei River in order to propose water quality index; (2) estimating point source (PS) and nonpoint source (NPS) pollutant; (3) establishing Total Maximum Daily Load (TMDL) procedures; (4) developing a plan for TMDL implementation; (5) presenting water quality improvement strategies for impaired water quality limited segment. River Pollution Index (RPI) in the past 5 years indicates that the Keelung Creek, the Sindan Creek and the Danshuei River segment were under moderate polluted level; the Jingmei Creek is between non (slightly)-polluted and lightly-polluted level. The achievement percentage for four general items is DO (55.6%~73.0%), BOD ( 87.7%~91.0%), ammonia-nitrogen (6.2%~17.6%) and SS (90.5%~96.4%). The result of the data shows that the segment of the Keelung Creek between the Dajhih Bridge to the Bialin Bridge is the main impaired segment. The estimation of the BOD loading generated from the catchment is 5,138 kg/day, including 2,512 kg/day PS and 2,626 kg/day NPS pollutant. The objective of the BOD TMDLs established in the document is to assure that the minimum BOD concentration of 5mg/ L is maintained throughout impaired segment from the Dajhih Bridge to the Bialin Bridge in the Keelung Creek. The WASP is applied to investigate different BOD loading scenarios under Q75 low flow condition. The result shows that the BOD has to be reduced by 3340 kg/ day to meet the critical water quality. Two scenarios are present in the BOD TMDLs. The PS and NPS loads of BOD simulated in the Scenario 1 present 65% PS and 65 % NPS loads reductions and the Scenario 2 present 50% point and 80 % nonpoint source loads reductions in this BOD TMDLs development.

Water Quality, TMDL, Water Quality Modeling.