Since 2008, the Taiwan EPA has carried out various plans of water quality improvement for rivers and reservoirs in Taiwan. In order to achieve the goal, the tasks of this project include :(1) analyzing the data of water quality collected from the reservoirs in order to propose water quality improvement strategies, (2) presenting nutrients reduction strategies for eutrophication potential reservoirs, (3) establishing nutrients reduction procedures and developing a plan for nutrients reduction implementation, (4) holding consultations with the departments involved. Literature on nutrients reduction strategies from USA and Japan is reviewed. The monitoring data of the 20 reservoirs between 1995 to 2016 are analyzed. The water quality of the eutrophication potential reservoirs, Mingde Reservoir and Shimen Reservoir, are investigated and evaluated based on the monitoring data in 2016, and the water quality improvement strategies of the two reservoirs are presented in this project. The EPA, the local government of reservoirs, and the experts discussed the water quality improvement strategies and watershed management of the two reservoirs. The TMDL for phosphorus and a load reduction strategy were developed for the Mingde Reservoir and the Shimen Reservoir. The simulated results indicate that the average annual total phosphorus (TP) loading into the Mingde Reservoir is 3,195 kg/year, which consists of nonpoint source loading of 2,337 kg/year estimated by SWMM/BASINS, and point source loading of 858 kg/year. The result shows that the TP loading has to be reduced by 31.0% to meet the critical water quality. The average annual TP loading into the Shimen Reservoir is 32,014 kg/year, which consists of nonpoint source loading of 27,044 kg/year, and point source loading of 4,990 kg/year. The Vollenweider mass balance model was used next to determine the trophic state under current pollutant loading and the load reduction needed to keep the reservoir from being eutrophic. It is estimated that the Shimen Reservoir can become the mesotrophic state if its average annual TP loading is reduced by 30.7% or more. The results provide the basis on which an integrated control action plan for both point and nonpoint sources of pollution in the watershed can be developed.

Reservoir, Nutrients, TMDL