- 學位論文
以CE-QUAL-W2模式模擬分析底層曝氣及入流水溫對新山水庫優養化水質改善之研究
Simulation and Analyses of the Effects of Hypolimnetic Aeration and Inflow Water Temperature on the Eutrophic Condition of Shin-Shan Reservoir by Using CE-QUAL-W2 Water Quality Model
摘要
位於基隆市的新山水庫為一離槽水庫，為基隆市及鄰近新北市區域之主要供水來源。近年來，水庫可能因過高的污染負荷及更為頻繁的極端氣候事件，水質優養情形日益嚴重。因此在本研究中使用CE-QUAL-W2水質模式，評估在水庫連續進行兩年的底層曝氣後，優養水質的改變情形。同時探討因極端氣候而導致入流水溫較庫內水溫高時，對於水庫水質的影響。 本研究分別以2010年及2011年的水庫實測數據，做為模式參數的校正與驗證依據。其結果顯示，以CE-QUAL-W2模式模擬新山水庫的水位及水溫等水理現象的變化情形，模擬結果大致良好。而總磷、硝酸鹽氮及葉綠素a為本研究中所欲模擬的水質項目，其結果顯示以2010年實測數據進行校正所得結果良好，但以2011年驗證時發生夏季時有低估總磷及葉綠素a的現象，但整體模擬的濃度變化趨勢仍與實際狀況相吻合。 模擬水庫進行底層曝氣的結果顯示，水庫底層的總磷濃度有明顯的下降。硝酸鹽氮則因更多的氨氮被氧化後，而有些微的上升。至於葉綠素a濃度，在曝氣的當年度並無明顯的變化情形，推測是因為底層曝氣無法改善表層水質；但曝氣後則能有效降低隔年的葉綠素a濃度，因此底層曝氣應能有效改善新山水庫的優養水質。 水質模擬結果顯示，當入流水溫升高後，水庫入流位置將會更為接近表層，若水庫呈現分層狀態時，便會使得入流營養鹽濃度積聚在表層，導致水庫優養情形更為加劇。 整體而言以CE-QUAL-W2模式模擬新山水庫水質結果尚屬良好。在水庫分層時期進行小量曝氣後，可有效抑制底泥中的總磷釋出，並可因此減緩隔年度的優養情形，所以欲進行水庫水質的改善，底層曝氣是具可行性的選擇。此外，模擬結果也顯示，若入流水溫上升，將會導致入流水由水庫表層輸入，後續便會出現藻類大量繁殖的情形，因此水庫相關管理單位在連續的高溫天氣狀態出現後，應密切注意水庫水質的變化。
並列摘要
During the past few years, Shin-Shan Reservoir, an off-channel reservoir and major water source for Keelung city and a part of Taipei metropolitan area, became seriously eutrophic due to elevated pollutant loading and possibly more frequent extreme-climate events. In this study, CE-QUAL-W2 water quality model was used to evaluate the effects of hypolimnetic aeration on water quality of Shin-Shan reservoir and to investigate the impacts of the higher temperature of inflow water than in reservoir during unusual climate events on the water quality. The model was calibrated and verified with the measured data in 2010 and 2011, respectively. The results of simulation show good fit to the hydrodynamic phenomena such as water levels and temperatures. However, the simulated results underestimate the total phosphorus concentration and concentration of chlorophyll a during the summer in 2011. Overall, the calibrated model provides a satisfactory fit of simulated results to the actual data in this reservoir. Simulations indicated a significant lower phosphorus concentration under the scenario of hypolimnetic aeration. The concentration of nitrate in the water body would increase slightly after a short period of hypolimnetic aeration due to the oxidation of ammonia to become nitrate, but would reach a steady state once most of ammonia had been transformed. The concentration of chlorophyll a would not change significantly with the hypolimnetic aeration in the current year, presumably due to less direct impact of hypolimnetic aeration on the surface water quality. Nevertheless, the concentration of chlorophyll a had an obvious decrease in the next year, due to the lower phosphorus flux released from sediments after hypolimnetic aeration in the previous year. In conclusion, the simulation analyses show that for a higher temperature of inflowing water than the temperature of epilimnion, the concentration of chlorophyll a would be increased in Shin-Shan Reservoir, which would have great impacts on the eutrophic state of Shin-Shan Reservoir.