氣候變遷及極端氣候事件對亞熱帶 水庫水質影響之研究

Abstract

氣候變遷在近年來持續引人關注，相關議題也早已不再局限於氣候方面。例如氣候變遷，也可能造成水資源短缺、水質惡化等不良影響。本研究試圖利用數個全球氣候模式以及不同排放情境所產生的合成氣象資料，與水質模式結合，模擬未來氣候變遷影響下水庫水質可能遭受之衝擊，探討氣候變化與水質之關係。 新山水庫是一個很典型的亞熱帶水庫，同時也是一個重要的飲用水水源。本研究以新山水庫為例，模擬受氣候變遷影響之新山水庫水質變化狀況，分析造成這一現象之具體原因。 本研究分析基隆地區歷史氣象資料，利用歷史資料的統計特性建立露點溫度、雲遮量以及日射量之模擬方法。同時根據TaiWAP工具合成氣象資料之原理，分別利用一階馬可夫鏈和指數分布降尺度得到日均溫度和日降雨量資料。 接著利用氣象合成模式和CE-QUAL-W2模式模擬2014年情形，模擬結果與實際情況相似，說明此組模擬方法對於新山水庫的模擬都有足夠的可信度。 未來情境模擬結果顯示，不論情境設定如何變化，溫度與水體溫度升高幅度都有良好相關性。全年平均藻類濃度濃度會增加，主要因素為溫度上升。同時在氣溫波動大的情境下，藻類濃度往往也會上升。這是因為冬季出現高溫時會帶動水體溫度升高，水體溫度一旦升高，熱量不易散失，更利於藻類生長。而極端氣象事件，例如連續高或低溫，對藻類影響不明顯，藻類濃度在此類環境中會略微減少。其他水質參數模擬方面，硝酸鹽與藻類濃度成負相關，溶氧與藻類濃度則是正相關。新山水庫中氨氮和總磷濃度都較低，因此只有在藻類變化濃度較大時，兩種營養鹽濃度才會比較容易看出變化，在未來情境下營養鹽濃度隨藻類增加會減少。 研究結果顯示，氣候變遷會對新山水庫水體產生一定衝擊，例如未來可能全年都會出現藻華，應該提前做好應對措施。 本研究運用氣象合成模式和CE-QUAL-W2模式模擬新山水庫之變化，此方法應可適用於其他水體的預測模擬。利用預測模擬可以提前知曉未來可能發生之狀況，便於相關單位提前做好應對措施，減小氣候變遷之負面衝擊。

Climate change became an important issue in recent year, and people’s concern is no longered limit to the change of temperature or precipitation. Climate change may also adversely affect water resource and water quality. This study was aimed to generate the meteorological datas of future with several Global Climate Models (GCMs) and different emissions scenarios, then with the application of CE-QUAL-W2 model, to simulate the water quality change under the impact of climate change, and to discuss the relationship of climate change and water quality. Shin-Shan Reservoir is a typical subtropical reservoir, also important as drinking water resource. This study will be focused on Shin-Shan Reservoir’s water quality with the influence of climate change. Methods to reconstruct the daily dew point temperature, the daily cloudiness and the daily total solar radiation by using statistical characteristics of meteorological data were developed based on Keelung historical weather data. In the meanwhile, we generate the daily temperature and daily precipitation by using 1st order Markov chain and exponential distribution, which is following the principle in TaiWAP Tools. Model simulation of the meteorological situation and the water qualities of Shin-Shan Reservoir in 2014 were performed. The result showed that the meteorological generators and CE-QUAL-W2 model have sufficient credibility. The simulation results of future scenarios showed that the daily temperature and the water temperature will rise parallel, regardless of which scenario is chosen. The annual average concentration of algae will increase due to the rise of temperature. Meanwhile the temperature with a large fluctuation will also cause the annual average concentration of algae to increase. The reason is that in winter the incidentally high temperature will lead to the rise of water temperature, and the heat of water is difficult to be dissipated because of the high heat capacity. On the other hand, the extreme weather events, such as a continuous high or low temperature, have no significant effect on the concentration of algae, which will decrease slightly. As for other water quality parameters, nitrate concentration is negatively correlated with algae, and that between dissolved oxygen and algae is a positive correlation. The concentrations of ammonia and total phosphorus are both low in Shin-Shan Reservoir. So the concentrations of ammonia and total phosphorus will decrease obviously, only when the concentration of algae has a large change. In a word, climate change will have a certain impact on Shin-Shan Reservoir. It is possible that the algal blooms occur throughout the year in the future. Therefore, some measures should be taken in advance. In this study, we simulate the meteorological data and water quality parameters of Shin-Shan Reservoir by using meteorological generator and CE-QUAL-W2 model. The same method can also apply to other waterbodies. Forecasting simulations can predict the future situations in advance, so we can reduce the negative impact of climate change by taking some effective measures.