氣象變化對進流河水水溫及離槽水庫水質之影響

The Effect of Weather on the River Temperature and the Water Quality of the off-channel Reservoir

王昱翔(Yu-Hsiang Wang)

指導教授 ： 吳先琪

國立臺灣大學/工學院/環境工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201600711

摘要

水庫是台灣重要的水資源設施之一，其水質之良窳影響公共給水之品質至鉅。土地的開發、集水區土壤及營養鹽流失及各種人為活動造成之污染，影響了水庫水質，使水庫優養化及淤積日益嚴重，以上皆是目前水資源管理單位所面臨的問題。離槽水庫之水質受到進流河水之水質與水文影響，本研究將以新山水庫為對象，以水質模式CE-QUAL-W2做為模擬工具，以浮昇射流模式進行預估進流進入水庫之位置，使其模擬更為接近真實流況。此外，並以驗證過的模式進行模擬，探討利用氣象資料預估進流水溫及其他水質相關參數等因子對於庫內優養化的影響，找出控制新山水庫發生藻華現象之方法。
本研究建立了利用氣象資料預測河川水溫之方法，以之模擬2014年與2015年河川水溫，預測水溫與實測水溫之年平均相對誤差約為5 %，而月平均相對誤差約在3~7 %。模擬的準確性高。
利用預估之河川水溫進行庫內營養鹽分佈模擬之情形可看出，在冬季完全混合時，庫內營養鹽分佈均勻；在夏季分層時期，庫內營養鹽受水體分層與入流水停留位置之影響，分佈不均。模擬結果顯示春、秋兩季，藻類分佈與真實情形相似，模式對於藻類生長之預測相當準確。此外，庫內藻類濃度與上層水營養鹽濃度具有高度相關性。若能於河川溫度較低的時進流，可抑制進流水因浮力因素突破斜溫層到達表層，降低表層水營養鹽含量而限制藻類生長。
透過氣象資料預測進流水溫度之準確度高，此方法搭配浮昇射流修正之CE-QUAL-W2對於警告藻華事件之發生及模擬未來氣候變遷之影響極有幫助，可提供未來管理單位選擇控制庫內水質方案的依據。
關鍵字：CE-QUAL-W2、河水水溫預測模式、浮昇射流、優養化、離槽水庫

關鍵字

CE-QUAL-W2 ； 河水水溫預測模式 ； 浮昇射流 ； 優養化 ； 離槽水庫

並列摘要

The reservoirs are major water facilities in Taiwan. The water quality of reservoirs will affect the quality of public water supply. Due to land overexploitation and human activities are deteriorating the water quality of the reservoirs. Problems of the eutrophication and the reservoir sedimentation are worse than before, which the water resource management has to face. In this research, we have investigated the effects of inflowing water temperature in addition to the water quality of Keelung river on a subtropical off-channel reservoir, Hsin-Shan Reservoir. By using the water quality model CE-QUAL-W2 as a tool and we did simulation of the algal concentration as well as concentration of nutrients with the estimation of the inflow position by the buoyant jet model to get the estimates as close as the real situation. Furthermore, we established the methods to estimate the river temperature and other environmental factors affected the eutrophication through the meteorological data. Finally, the method to control and prevent the algae bloom in Hsin-Shan Reservoir will be discussed.
In this study, in order to simulate the river temperature, respectively, we established the model to predict the river water temperature by using weather information. The results show that the average relative error is about 5% between the predicted river water temperature and the real water temperature. The monthly average relative error is about 3 to 7%. In general, the simulation of river water temperature has reasonable accuracy.
With estimated river water temperature, the simulation results indicate that the nutrients were completely mixed in the reservoir at winter, and was unevenly influenced by the thermal stratification and the final position of the inflow in summer. The model can accurately simulate temporal and spatial variation of the concentration of algae. Besides, we found that algae concentration in reservoir has highly correlation with the amount of nutrient supply to epilimnion. The nutrient supply to the surface water and algae growth would be reduced if the inflow temperature is low enough to avoid breaking into the thermocline to the surface on account of the buoyancy of the inflow water.
With high accuracy of the estimates of the inflowing water temperature, CE-QUAL-W2 model with the consideration of the buoyant jet mechanism are able to simulate the water quality of Hsin-Shan Reservoir very well. The method can not only alert to the occurrence of algal bloom but also predict the impact of the climate change in the future. Therefore, the authority of Hsin-Shan Reservoir should closely watch the temperature of river water and choose appropriate operational approach to preserve the water quality in the reservoir when it is continuously climbing up within a short period of time.
Keywords:CE-QUAL-W2、river temperature prediction、buyant jet mechanism、eutrophication、off-channel reservoir

並列關鍵字

CE-QUAL-W2 ； river temperature prediction ； buyant jet mechanism ； eutrophication ； off-channel reservoir

參考文獻

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