圖書典藏及影音數位平台

溫室氣體所造成的全球氣候變遷已然成為眾所關注的議題，氣候變遷對台灣水資源之影響亦已見其徵，經濟部水利署除積極投入在氣候變遷對水庫之衝擊與調適上進行深入研析，亦已針對再生水、自來水等碳足跡進行相關評估作業，而水庫壩堰等蓄水、引水水資源系統尚未完成系統性之評估研究，為加強水庫系統碳足跡評估並研擬整體低碳策略，爰擬辦理本項計畫。 本計畫主要目的係延續去年(100)度的調查評估，強化水體通量調查技術，透過追蹤國內外之水庫系統溫室氣體調查方法，實際調查水庫水體排碳量數據，建立適用台灣水庫系統的溫室氣體參數資料庫。另外，更進一步納入水資源工程溫室氣體排放評估，工程活動除為水資源碳足跡計算範疇，亦為規劃階段必須面臨之課題，將一併深入探討。本計畫可以充實水資源全生命週期之溫室氣體評估，因應環境影響評估與溫室氣體減量法之實施，並綜合彙整各計畫成果，提供水資源領域因應氣候變遷減緩及調適策略之具體策略與決策資訊。

This project aims to strengthen local measurement and analysis methods for waterbody of reservoirs based on the results of previous projects. Furthermore, clearer considerations about lifecycle were applied in this project to propose carbon footprint of reservoir systems and water supply chain. All the analysis results and discussion help to systematically understand current carbon emission status of reservoirs. Accordingly, more precise and effective carbon mitigation and energy saving strategies for water resources development and supply can be generated toward those critical carbon emission contributors. In this project, carbon management and control related standards and regulations were surveyed and reviewed. In accordance with the concept of carbon footprint calculation, carbon emissions of the water supply chain can be regarded as the emission of six stages, including water source abstraction, water conveyance, water treatment, water distribution, water use and wastewater treatment. It is shown in the international references that the water use stage is the highest carbon emitting source of the water supply chain, and followed by the wastewater treatment stage. However, local studies for carbon emission assessment of wastewater treatment processes were comparatively rare. For this reason, carbon emission assessment or inventory of the two stages, water use and wastewater treatment, should be the prior tasks to overall understand the local carbon footprint of water supply chain. More useful information and indicators can be subsequently applied to improve the efficiency and effectiveness of carbon emission control of water resources supply. Ggreenhouse gas (GHG) may emit from the water body of reservoir. Many factors (the ambient, water quality and sediment) influence the production, transfer and emission of greenhouse gas. A main reason that GHG generates is that the plants dies because it was submerged during the reservoir filling. The microorganism decomposes the organic matters, and produce carbon dioxide (CO2) in aerobic environment, methane (CH4) in anaerobic environment and nitrous oxide (N2O) in nitrification/denitrification process. On the other hands, carbon dioxide may be absorbed by the water body as carbonic acid reacts with alkali substances, or is reacted in the photosynthesis. The possible factors influencing the GHG emission are the climate, water quality, ambient and human activities. Summarizing the survey in literatures, the reported factors may include the organics, nutrient, temperature, dissolved oxygen, planting density, aqua ecology, water retention time in the reservoir, wind speed, the reservoir type and water depth. In order to clarify the GHG emissions from water body of local reservoirs, four reservoirs, Feitsui, Liyutan, Nanhua and Tsengwen, were selected as the examing cases for 1-yr long GHG measurement in this project. The filed measurement was initiated from the fourth season last year using the most suggested method evaluated in the former three seasons. The measurement results in this Octobor and last year was combined and analyzed by multiple regressions to verify the possible relationship between GHG flux and water quality / sediment component. We have noticed that the instantaneous flux is not capable to represent the emission pattern. Annual average with seasonal data may be a better option. The results shows that the methane and nitrous oxide flux are close to the reported value of the reservoirs in temperate zone in literatures. CH4 flux is 4.0 mg/m2/day for Liyutan, 6.8 for Feitsui, 30.8 for Tsengwen and 13.3 for Nanhua reservoir. N2O flux is 0.4 mg/m2/day for Liyutan, 0.5 for Feitsui, 0.8 for Tsengwen and 0.4 for Nanhua reservoir. For carbon dioxide, the flux is -652.4 mg/m2/day for Liyutan, -351.5 for Feitsui, 346.7 for Tsengwen and 466.8 for Nanhua reservoir. All data of the four reservoirs are used to establish three multi-variable equations (GHG flux vs water quality), while only the most influential variables are selected. The results are described below. (1)CO2: the influential factors include TOC, SS, ammonia nitrogen, chlorophyll a, pH, room temperature and water level. (2)CH4: the relating factors include TOC, SS, pH, room temperature and water level. (3)N2O: the relating factors include TOC, SS, ammonia nitrogen, chlorophyll a, pH, room temperature and water level. Noticeable, there is an optimal regression model for each reservoir for using water quality data to estimate GHG flux. The specific model for one reservoir may not be suitable for another reservoir. Using regression model to estimate GHG flux by water quality data may not be universal for all reservoirs. On-site measurement is recommended if the budget is affordable. After the reference review and discussion, the boundary and scopes of carbon assessment for water resource construction were identified by the carbon footprint consideration. Total five categories of carbon emission sources should be taken into account, which are materials, energy and resources, landuse change, waste treatment, and transportation. However, only emissions from materials and energy consumption were calculated at the design stage according to the constraint of data availability. At the operation stage, all the five categories were concerned and calculated with its physical records. Major carbon emitting sources among all activities of the reservoir construction were screened by the calculation results in the Tienhuahu reservoir whole lifecycle carbon emission assessment project. According to the numbers, dam construction was the largest emitting source comparing to other works. Differ to only core and shell constructions of the Hushan reservoir were discussed last year, more cases at the design stage and also more specific field data were included in this part. Accoring to the latest emssion factors, we reviewed and calculated the amount of carbon emission during the construction phase of the Tienhuahu reservoir again. The results shows about 33% total emission increase compared to the calculation done in the previous project. The increase caused mainly from the change of the diesel emission factor, which was not with lifecycle concern in the previous calculation. As the dam consctruction of the Tienhuahu reservoir mainly consists of earthworks, which means a heavy fuel consumption duty, its carbon emission resonably obviously raised with the diesel emission factor. Gautai reservoir is a new case in this study for carbon calculation of reservoir construction. The emission amount was evaluated by existed design data of the Hushan reservoir, which is not the same type as the Gautai reservoir. Therefore, the number shows in the carbon calculation result may has uncertainty. The results shows that differ to the Tienhuahu reservoir, the main emitting sources are construction materials such as concretes and steel bars. It is because Gautai reservoir is designed with a concrete dam, which is a heavy material consumption work. In order to verify and enhance the calculation results obtained last year, more field data of the Hushan reservoir had been collected this year for advanced discussion. The result, analyzed from the real data offered by the contractor, shows that carbon footprint of dam construction (only take fuel consumption into consideration) was around 4.45kgCO2e/m3. It is much lower than the result 7.35 kgCO2e/m3 that calculated by the design data. The reason might be either over estimation of operation duration or energy consumption coefficients of construction machinery. Taking functions of the reservoir into consideration, the construction activities related to water storage capacity and water supply were prioritized to be the case study. Therefore, the two popular reservoir dredging activities, land excavation in the river basin and sediment dredging, were chosen as the representative construction works at the O&M stage of the reservoir in this study. The calculation was done both with the design and measurement data from Nanhua and Tsengwen reservoir management office and the contractors of the O&M projects. In the same way, emission amounts per unit loading were proposed. Construction carbon footprints calculated by both design and real data for unit earth excavation mass were 14.48kgCO2e/ton and 9.68kgCO2e/ton in Nanhua reservoir. Carbon footprints per unit earth excavation mass in Tsengwen were also generated as 11.58kgCO2e/ton and 6.92kgCO2e/ton. For sediment dredging works, the calculation was finished according to both design and measurement data collected by one project in Nanhua reservoir. The result shows 9.83kgCO2e/m3. The differences between organizational cabon emission and carbon footprint calculation were reviewed and defined in this study. The most critical differnces were the assessment scopes and the selection of emission factors. Carbon emission related activities that may occur in the reservoir management system were identified. In order to make examples, all carbon emission activities data (both natual and anthropogenic sources) had been collected and arranged to calculate annaul emission for the four selected reservoirs. Among the four reservoirs, their 2012 annunal emssion amounts were between 542~7,232tonCO2e. Direct emission (Scope 1) was the major emitting source, which occupies about 66%~92%. The carbon footprint calculation used per cubic meter water output as the funtional unit. And the result shows that the annul carbon footprint of unit water supply for the four reservoirs were 0.0023~0.0244 kgCO2e. The Carbon Calculation Standards and Guidelines were first proposed in previous project in 2011. In order to improve the understanding and application of all the results of the related projects, most of the experiences and conclusions were further condensed to revise the Carbon Calculation Standards and Guidelines. The draft revision edition was presented as an important result of this study. There are seven chapters in the standard and five chapters in the guideline, which were matched for each other to instruct efficient execution of carbon emission calculation and measurement. After all the discussion in this study, low carbon strategies relating to water supply were concluded in two phases. One focused on the life cycle of a reservoir. The carbon reduction solutions were proposed with each stage, including the plan and design stage, the construction stage and the operation stage. The other one emphasized on the life cycle of water. The carbon reduction were thought with each stage, including water storage, water conveyance and treatment, water distribution, water use and wastewater treatment. Comparison of different water supply alternatives and multi-sources water supply plan were also discussed as supportive information for related decision making in the future.