The goal of this project is to investigate the suitability of Carlson trophic state index (CTSI) for the management of drinking water reservoir in Taiwan through the survey on water quality of high eutrophication potential candidates and the analysis of influencing factors towards algal growth. Then, the mechanisms of management in early warning of problematic water quality for reservoir and water treatment plant will be established. Finally, the draft of water quality index advancing plan for drinking water reservoir will be proposed. It is anticipated that Environment Protection Agency (EPA) would improve the effectiveness in water quality management for the guarantee of safe drinking water in the future based on the advanced mechanism in water quality management. The results of water quality analysis for four candidates (i.e., Shimen, Baoshan, Liyutan and Hushan reservoirs) showed that diatoms and green algae are predominant in each reservoir, while blue-green algae growth potential would increase at summer season (from June to August) for Baoshan, Liyutan and Hushan reservoirs where thermal stratification is particularly pronounced. In addition, algae density and chlorophyll a (Chl-a) are well correlated (P=0.81). Thus, Chl-a is proposed to be a proper indicator towards algal growth potential and water quality management for Taiwan reservoirs. The administration of reservoirs can use Chl-a as an alternative indicator to evaluate the trophic state of reservoir water. In Taiwan, the mechanisms of management in early warning of algae bloom for drinking water reservoir and water treatment plant mainly focus on the prevention of algae toxin event and its response. The administration of reservoir periodically takes a visual check if the algae bloom occurs, while water plant use on-line total organic carbon (TOC) analyzer to check TOC level and then judge the occurrence of algae bloom. As algae bloom occurs, the administration of reservoir would take action to change water source or water intake level to avoid algae-laden water supply to water plant, while water plant would adopt other dosing approach and dosage (e.g., chlorine and coagulant dosage) or increase the washing frequency of sedimentation tank and sand filter. In summary, the key point to improve the effectiveness of water quality index in reservoir management is the consistence in the goal of water management and the index selection. Then, the administration of reservoir can implement self-management in water quality, and EPA can also significantly improve the effectiveness of drinking water safety management through the value-added application of Chl-a index in drinking water quality management system. On the other hand, the promotion brochure of water quality index for drinking water reservoir management has been edited with the introduction of trophic state index, the cause and meaning of eutrophication and the purpose and effectiveness of water quality index. Meanwhile, “the draft of water quality index advancing plan for drinking water reservoir” and its guide book has been proposed for the promotion of the index as well as improvement in water quality management by EPA.

Water quality index, Carlson trophic state index, Chlorophyll a