Laogei Creek, located in Tao-Yuan County, has been contaminated with multiple contaminants due to the establishment of designated industrial areas, randomly distributed animal farms and agricultural fields, and lack of sewer connections for discharge of municipal wastewater. The quality water of Laogei Creek has deteriorated throughout the years. Therefore, Environmental Protection Administration (EPA) has identified Laogei Creek as a priority to improve its water quality with the goal of no odor and sufficient dissolved oxygen (DO), and decided to develop a Total Maximum Daily Load (TMDL) for DO, suspended solids (SS), ammonia (NH3-N) and biological oxygen demand (BOD) for the Laogei Creek watershed, as the pioneer project to set up a TMDL framework. To establish the framework for TMDL for Laogei Creek, this project has goals as follows. 1) Based on the existing literature and data collection, we have constructed the inter-relationship between the water quality and the wastewater discharges from point and nonpoint sources. 2) We have estimated the impact of the additional wastewater discharges from the newly developed high-tech industry in the Laogei Creek watershed. 3) We have set up a standard procedure to regulate and to permit the party involved in wastewater discharges. This project mainly focused to regulate the water quality control of Laogei Creek by establishing a TMDL for all possible contaminants. This project analyzed wastewater discharges from the point and nonpoint sources, such as agricultural and stormwater runoff, to set up a model for further permitting. QUAL2K has been generally applied to simulate the effect of hydrological coefficients and water quality of natural water bodies and artificial channels on the function of transport or diffusion. QUAL2K, a one-dimension model, can be used to estimate such hydrological coefficients of water bodies and sustainable balance. This project has adopted QUAL2K to simulate the hydrology and water quality of Laogei Creek. The model was trained provide a linkage between the discharge from point and nonpoint sources, and the receiving water. The model is used to calculate the wasteload allocations (WLA) for point sources and load allocation (LA) for nonpoint sources for SS, NH3-N and BOD, each with the consideration of 10% margin of safety (MOS). Besides, a water quality model can be used to assess the environmental impact from additional high-tech wastewater discharges as well as to estimate wasteload and load allocations. The high-tech wastewater was proposed to be discharged to upstream Laogei Creek. Based on the volume and the concentrations of constituents committed by two companies, the discharge of the wastewater would not cause adverse impact. On the contrary, it slightly increases the WLA and LA for BOD and NH3-N due to the increase of the flow volume. Concentration of NH3-N in Laojei Creek would also improve if the high tech industries can commit to reducing the concentration of NH3-N at the effluents. It is suggested that more information regarding the land use, soil composition, unban stormwater runoff, and weather to be collected. It would also be beneficiary to understand the ecological systems in watershed, which to be considered as important uses, and to be used to determine the practical water quality objective for beneficial uses protection. To ensure the effectiveness of the TMDL, additional monitoring shall be required. This project also identifies and suggests the necessary update of industrial permit to accommodate new effluent limits and sampling requirements.

Total Maximum Daily Load;TMDL, River water quality;QUAL2K