| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 106 === The water treatment type constructed wetlands (WT-CWs) are the artificial wetland system mainly constructed for wastewater treatment. Its design principle is to construct a wetland that mimics the function of natural wetlands by ecological methods. The management and restoration of the existing CWs are based on the experience. The quantitative evaluation of health conditions for WT-CWs, however, have not yet been fully established. The comprehensive indicators simultaneously considering the hydraulic efficiency and ecological richness to describe the health levels of WT-CWs have not developed yet. In this study we conducted the Index of Wetland Condition (IWC), which is commonly used to assess the health condition of natural wetlands, to evaluate the conditions of WT-CWs and improve the effectiveness of the management.
The study region was Lujau Creek Constructed Wetland in New Taipei City, where the wetland condition was claimed necessary for restoring. We conducted SRH-2D to simulate the water area and water depth and analyzed the hydraulic retention time of it. Comparison between the original and the current conditions of the hydraulic retention time of each treatment unit it demonstrated that the treatment function of this wetland is degraded. Moreover, the IWC with 27 sub-indicators was evaluated with data measured from 2014 to 2016. The results show that the IWC does not reflect the health status of the Lujau Creek Constructed Wetland. The sensitivity analysis of IWC was also conducted. According to these results, bird diversity and bird abundance were not the most sensitive indicators, even though they should be important indicator in wetland conditions. This study tried to modify the IWC soring system with the method to change the weight and lengend range. The modified IWC (MIWC) showed that it can correctly reflect the health status of the Lujau Creek Constructed Wetland. The sensitivity analysis of MIWC, on the other hand, showed that the indication of the bird diversity was improved. MIWC again was applied to the Shuimokeng Stream Constructed Wetland in the Guandu Nature Park, where the wetland condition is stable. It porved that MIWC can also reflect Shuimokeng Stream Constructed Wetland with the health status.
This study shows that the consideration of IWC are general and versatile; and suitable to be modified for Water Treatment Type Constructed Wetlands as the specific index. With this proposed MIWC as the indicator, the wetland can be quantitatively managed. Moreover, based on the case studys we showed that MIWC could increase the sensitivity of waterfront vegetation diversity sub-indicators and bird diversity sub-indicators.
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