永續性水質管理系統受氣候變遷影響之脆弱度評估

Abstract

永續發展意涵是在不導致生態環境退化下持續經濟與社會發展，確保發展導致之累積衝擊不超過環境承載力，永續性環境管理為以環境承載力為總量規範經濟與社會之發展，然全球暖化所引起的氣候變遷會改變環境承載力，進而影響永續發展。河川涵容能力為重要之環境承載力，其會受到水溫、水文、環境背景污染質等因子之影響，氣候變遷可能影響此三項主要因子，進而影響河川涵容能力。 本文首先探討河川水質與涵容能力之主要影響因子，並評估其受氣候影響之可能性，進而根據氣候變遷情境，評估對水質與涵容能力的衝擊。本研究採用在台灣地區可提供良好模擬結果之GWLF（Generalized Watershed Loading Functions）模式中之河川流量模組作為流量之分析工具，並應用水質模式QUAL2E評估目前與未來氣候變遷下，河川BOD5與DO濃度可能之影響為何。本研究流程首先由氣候變遷分析所得之降水在時空分布上之變異，以水文模式推得可能產生的流量變化情形，進而由水質模式評估氣候變遷對河川水質與涵容能力可能的衝擊，並根據分析結果探討未來相關調適策略方向，且可供環境管理者訂定水質標準與管理涵容能力之參考。 本研究以頭前溪為例，結果顯示氣候變遷會導致水溫上升、並隨時間演進有枯水期流量減少及BOD5濃度上升趨勢，進而會造成BOD5污染涵容能力下降。

Sustainable development is to continue economic and social developments without degrading environmental quality and to keep cumulative impacts from exceeding the environmental carrying capacity. The sustainable environmental management strongly depends on the variation of environmental carrying capacity caused by the climate change. Stream assimilative capacity is an important environmental carrying capacity which is related with key factors, including water temperature, streamflow, and background pollution. Climate change may influence these factors and further affect the stream assimilative capacity. Therefore, the main factors which affect the stream assimilative capacity and water quality are discussed in this study and used to assess the impact with different climate change scenarios. A conceptual and physical model, Generalized Watershed Loading Functions (GWLF), is applied to simulate the stream flow under different climate. Meanwhile, a water quality model (QUAL2E) is used to estimate the concentrations of BOD5 and DO with those variable stream flows. At last, the results of climate change impact assessment on stream assimilative capacity can be used to address the directions of future research on adaptation and also provide useful references to setup water quality standard and to manage assimilative capacity. The Tochen River is taken as a case study in this study. The results indicate that the climate change increases the water temperature, decreases the streamflow in dry seasons, and leads to higher BOD5 concentration and lower stream assimilative capacity.