翡翠水庫營養鹽之總最大日負荷規劃

Developing A Nutrient TMDL Program in Feitsui Reservoir Watershed

吳政緯(Cheng-Wei Wu)

指導教授 ： 朱子偉

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2010年)

https://doi.org/10.6841/NTUT.2010.00565

摘要

翡翠水庫係供應大臺北地區民生用水的單一目標水庫，近十年來臺北翡翠水庫管理局之水庫水質監測資料顯示水質有逐漸呈優養化傾向，主因推測為農業活動與北宜高施工和通車後產生之非點源污染所造成。
本研究主要目的係應用非點源污染模式－SWAT（Soil and Water Assessment Tool）模擬翡翠水庫集水區內水文、泥砂及營養鹽之傳輸情形，再考慮甲類陸域水體水質標準，研擬翡翠水庫營養鹽之總最大日負荷規劃（Total Maximum Daily Load, TMDL），同時針對超出分配量之污染負荷，訂定數種污染削減方案，以期能達到保護水庫水質和維持健康的水生態系統之目的。
研究收集1997年至2007年翡翠水庫集水區之氣象、水文與地文資料以進行模式之模擬，並選用1998至2002年中坪林站與翡翠水庫大壩站的流量、泥砂和水質資料執行模式自動檢定，再以2003至2007年的資料驗證模式模擬集水區與水庫的結果。集水區月流量經檢定和驗證後，效率係數分別為0.97和0.54，月泥砂量檢定和驗證之效率係數分別為0.91和0.33，而月總氮檢定和驗證之效率係數分別為0.57和0.66，月總磷效率係數則分別0.41和0.15。水庫的模擬結果則顯示水庫的月入流量檢定和驗證之效率係數皆為0.97；月總氮輸入量在檢定和驗證之效率係數分別為0.93和0.81，月總磷輸入量則分別為0.84和0.18。綜合以上結果說明SWAT模式具有模擬集水區在不同土地利用、土壤分佈與管理作業下長期水文暨水質反應的能力。
本研究根據甲類水體水質標準，針對氨氮、硝酸態氮及總磷三種營養鹽於翡翠水庫集水區進行TMDL規劃。模擬結果顯示，氨氮與硝酸態氮負荷皆小於TMDL的要求，而總磷負荷（78,481公斤/年）則超過TMDL的容許值（65,411公斤/年）。說明水庫水質尚佳，但為了達到甲類水體水質標準，必須削減16.67％之總磷負荷。
研究共挑選五種較適合設置於翡翠水庫集水區內農業用地之最佳管理措施（Best Management Practices, BMPs）進行模擬，其中包括草溝（Grassed Waterway）、過濾帶（Filter Strip）、逕流滯留池（Detention Pond）、作物階段種植（Terrace）及關鍵區域栽種（Critical Area Planting），並將BMPs設置於翡翠水庫集水區內主要關鍵區域與主要及次要關鍵區域之茶園用地，以及翡翠水庫集水區內所有茶園用地與所有農業用地，同時探討三種BMP組合方式針對總磷負荷進的削減效果評估，其中第一種組合為設置草溝、過濾帶、逕流滯留池及作物階段種植；第二種之組合為在茶園用地設置過濾帶、作物階段種植及逕流滯留池，並於茶園用地附近荒地進行關鍵區域栽種；而最後一種則為五種BMPs皆設置之組合。總磷削減率模擬結果顯示於翡翠水庫集水區內所有茶園用地設置第二種（16.69％）或第三種（20.23％）之BMP組合，以及於所有農業用地設置第二種（21.40％）或第三種（26.83％）之BMP組合皆可達到TMDL規劃對總磷削減之要求，亦即水庫水質可滿足甲類水體之水質標準。

關鍵字

非點源污染 ； SWAT模式 ； 總最大日負荷 ； 營養鹽 ； 最佳管理措施 ； 草溝 ； 過濾帶 ； 逕流滯留池 ； 作物階段種植 ； 關鍵區域栽種

並列摘要

The Feitsui reservoir is the major source of water supply for the Taipei metropolitan area in Northern Taiwan. The reservoir water quality has been well protected by associated authorities. However, recent monitoring data of the Feitsui reservoir and researches suggest that the water quality have be reached the near-eutrophic state, especially when Taipei-Ilan expressway was built and came to operate.
This study aims to develop Total Maximum Daily Load (TMDL) program for nutrient control in Feitsui Reservoir watershed by applying the Soil and Water Assessment Tool (SWAT). SWAT is a complex, physically based, and continuous time model with spatially explicit parameterization capability; it intends to analyze the hydrologic and water quality response resulting from alternative watershed managements.
The ten-year data (1998-2007) of hydrology and water quality are used to calibrate and validate the model. Moreover, the validated SWAT model will be employed to evaluate the long-term water quality impacts due to the implementation of several BMP (Best Management Practice) scenarios. In the first place, the results of TMDL development show that the simulated average annual TP loading (78,481 kg) has exceeded the maximum allowable loading (69,586 kg) which was calculated based on the water quality standards of Category A water bodies. Therefore, second BMP scenarios were developed to reduce TP loading and elevate the water quality within standard of Category A. The BMP simulations indicate the best scenario, consisting of grasses waterway, filter strip of 15m, detention pond, and terrace implemented on all tea farm and all agricultural land in combination of critical area planting on adjacent barren land, will reduce 26.83% of TP loading to satisfy the water quality standard. Last but not the least, the thorough TMDL plan will provide a useful schematic BMP allocation for water quality improvement and protection within specific standards.

並列關鍵字

nonpoint source pollution ； SWAT model ； TMDL ； nutrient ； BMPs ； grassed waterway ； filter strip ； detention pond ； terrace ； critical area planting

參考文獻

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