集水區水質健檢分析及污染削減策略評估－以湖山水庫集水區為例

本研究透過水庫水質水量保護區健檢，分析集水區各項觀測資料，挑出影響水庫水質及庫容永續的潛在危害因子，一者在去除或削減點源及非點源污染，二者在加強區域內水土保育，使相關單位可依其結果及早介入，以預防原水高濁度災害並促進水質之穩定功效，以確保水庫永續利用與穩定供水之標的。經本研究調查分析湖山水庫水質水量保護區內各子集水區之水質環境後，水質環境評估係根據SWMM所分析之桶頭攔河堰以上集水區各子集水區污染量成果，並根據單位面積污染負荷量、點源污染以及污染貢獻占總量比例等排序結果，選出S2（支流毛生樹溪集水區）、S5（支流阿里山溪集水區）及S1（桶頭攔河堰以上主流部分）分別為前三名之污染熱點，故選上述三個子集水區作為目標，以熱點之方式進行總磷污染削減及策略模擬。了解熱點區域分布在S1、S2及S5，皆是農地與建物之聚集地，聚落之生活污水所產生之點源污染，以及農地所產生之總磷非點源污染，於湖山水庫集水區廣設LID（low impact development，低衝擊開發設施），達到污染在地處理後排放。當全區控制時，如情境六－同時管制點源及非點源污染（同時控制點源污染排放濃度削減至2 mg/L與非點源污染負荷減少50%），則總磷平均濃度可降至40 μg/L以下。

關鍵字

集水區健檢；總磷污染削減；集水區管理

並列摘要

Through assessing the basin of Hu-Shan reservoir, this study analyzes the observation data in watershed of the reservoir, and identifies potential threads affecting the water quality as well as sustainable storage capacity of the reservoir. Firstly, to reduce the point source and non-point source pollutions for water quality. Secondly, to strengthen water and soil conservation in the watershed for reducing sediment laden inflow into reservoir; which means, based on the results, the concerned authorities can intervene as quick as possible in order to promote the stability of water quality as well as prevent the consequence of high turbidity in the raw water, ensuring sustainable utilization and stable water supply by the reservoir. After investigating and analyzing the water quality condition of each sub-catchment area of the Hu-Shan Reservoir, this study assesses the water quality environment of pollution loads in each sub-catchment of the watershed above Tongtou diversion weir according to SWMM analysis. Based on the ranking of pollution load per unit area, point source pollution, and the pollution contribution ratio to total amount, three top pollution hot spots were chosen, which are S2 (the Shengmaoshu tributary catchment), S5 (the Alishan tributary catchment) and S1 (The mainstream above Tongtou diversion weir). Then the three sub-catchment areas become the targets of strategy simulation for pollution reduction. The hot spots, distributed in S1, S2 and S5, are the human settlement and gathering of agricultural lands, where the point source pollution is caused by the untreated domestic sewage, and the non-point source pollution, such as total phosphorus, is generated from the agricultural lands. Our strategy, by simulation, for pollution reduction is to widely set up feasible LID (Low Impact Development) facilities for the purpose of pollutant discharge after on-site treatment in the watershed of Hu-Shan Reservoir. When the hot-spot area is under control, such as scenario 6, simultaneous control of point sources and non-point sources, the emission concentration of the point source pollutants can be reduced to 2mg /L and non-point source pollutants reduced by 50 %, the average concentration of total phosphorus can be reduced to less than 40 μg/L.