| Summary: | 碩士 === 淡江大學 === 水資源及環境工程學系碩士班 === 104 === Water quality index and water quality models are usually used to demonstrate the trophic states of reservoirs water quality. In Taiwan, the Carlson Trophic State Index (CTSI) is officially used by Taiwan EPA. The objectives of this study are to understand the trophic states of 20 main Taiwanese reservoirs with different water quality indices and moreover, to compare the results of Vollenweider model and water quality index used in Nanhwa reservoir. The purposes of this study were: (1) to evaluate the limited nutrient of eutrophication for the 20 reservoirs, (2) to compare the differences of various trophic indices, (3) to evaluate the pollution loadings and water quality of Nanhwa reservoir by SWMM (Storm Water Management Model) and Vollenweider model, (4) to compare the trophic states of Nanhwa reservoir by Vollenweider model and trophic indices. Moreover, trophic state index on single parameter of total phosphorus (TP) included Carlson, USEPA, OECD and OECD average.
The results show that about 80% of N/P ratios are larger than 15 for the main 20 reservoirs in Taiwan, so that the limited nutrient of eutrophication is phosphorous. The total phosphorous (TP) is suggested as the target water quality for reservoir management. While using the CTSI as the trophic state index, the percentage of eutrophication of the 20 reservoirs is 31%. However, the results are different with other indices. The percentage of eutrophication according to TP is 18%(OECD average TP), 15%(OECD TP), 46% (USEPA TP) , and 34% (Carlson TP), respectively. The validated SWMM model resulted in 5,603 kg-TP/yr pollution loads from Nanhwa reservoir watershed. The results of Vollenweider model also showed that the trophic state of Nanhwa reservoir is mesotrophic state, which is consistent with the results of other indices. If the target TP concentration is set as 10 µg/L for Nanhwa reservoir, 32% and 47% of the TP loads should be reduced respectively, according to the annual average and seasonal average results from Vollenweider model.
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