大甲及大安溪流域水量改善策略對BOD之影響研究

Abstract

本研究以系統動力學為基本分析工具，並以大甲及大安溪流域為研究區域，建立涵蓋水量調配與水質影響之區域水資源策略分析模擬模式。並進一步就現有系統及增加越域引水、興建人工湖及自來水管線汰換等不同調適策略，應用所建置之模式探討各改善策略對生化需養量（BOD）之影響。 現況建立流域河川及水庫水質系統動力模式，再結合水資源調配系統動力模式，推求德基水庫及其河川的BOD。水庫部份以二次規劃法推求不同土地形態下的單位面積負荷係數及流達率，配合降雨量分配，進一步推求水庫BOD。河川BOD的流達率亦以二次規劃法推求。案例模擬發現，其中越域引水及興建人工湖策略會造成下游河段BOD惡化，自來水管線汰換策略則會讓BOD變好。故對河川BOD影響而言，以自來水管線汰換策略影響最小。 結果顯示本研究發展之流域水量水質模式，可探討不同水量改善策略對於BOD的影響，提供更完整之參考資訊，以為決策者參考。

This research develops an integrated simulation model that combines water quality and water quantity simulation models by using system dynamics (SD). A proposed model was applied to assess performance of various policies on sustainable water resources management of Dajia and Daan basin. This assessment focused on evaluating the impacts of water resources developing alternatives on reservoir and river water quality. Two supply-side strategies - Taichung artificial lake and trans-basin diversion, and one demand-side strategy - water supply pipelines replacement, were examined by using the model with The Taichung basin as studied area. Parameters related to water quality modeling were calibrated by using the quadratic programming. The water quality simulation model consists of two parts; simulation of BOD transport on reservoir upstream catchment and that on reservoir downstream river. BOD loading coefficients for different landscapes and transport coefficients of BOD in river flow were calibrated. Simulation results indicated that BOD concentration in river downstream section will increase and surpass the water quality criteria after a trans-basin diversion and Taichung artificial lake were constructed. On the contrary, the BOD in the downstream river section will decrease after a water supply pipeline replacement. The results demonstrated that the proposed policy assessment model can effectively investigate the performance of various scenarios and is a valuable tool for supporting the decision making of integrated basin management.