以最佳管理作業優選配置法控制水庫集水區非點源污染

Abstract

近年來台灣地區已開始重視非點源污染之管制，對於非點源污染之控制方法，即最佳管理作業（Best Management Practices, 以下簡稱BMPs），亦有不少相關研究。雖然現行之水土保持法規已提供吾人建置相關之水利設施以滯留暴雨時期所產生之逕流量和泥砂量；然而，這些水利設施之設置通常僅針對局部小區域來考慮，並未針對整個廣泛集水區域以系統方法加以考量。本研究之目的即以整個集水區及水庫為研究範圍，建立一優選模式以決定集水區內BMPs之配置較佳方案；本研究選用3種結構性BMPs，分別為：濕式滯留池、草溝和入滲溝。本模式包括3個重要部份：集水區模擬模式（採用HSPF模式)；水庫水質模式（採用CE-QUAL-W2模式）及優選模式（採用遺傳演算法GAlib 軟體）。 本研究以翡翠水庫為例，利用遺傳演算法進行求解，採用總年計成本最小為優選模式之目標函數，限制式則為污染物濃度須達標準，包括總懸浮固體（Total Suspended Solid, TSS）、磷酸鹽（Phosphorus, PO4）等水質項目須達到水質標準。研究中模擬2002-2003共2年之流量及非點源污染量及水庫水質模式，以模擬逕流量與營養鹽在河道及水庫中之實際情形，所獲致之結果可提供水庫集水區未來實施非點源污染管制時之參考。

The nonpoint source pollution control is in the beginning stage in Taiwan. The techniques of nonpoint source pollution control, that is Best Management Practices (BMPs), already have several related research. Although the soil and water conservation law provides regulations that the land developer should capture the exceeding stormwater runoff and sediment due to any significant development in the watershed. Most of stormwater controls have been designed at the local, or on-site level, but not at the regional or watershed level in a comprehensive and systematic manner. The purpose of this study is to establish an optimization model for the optimal placement of structural BMPs at the watershed scale. In the research, three types of structural BMPs are selected, including wet detention pond, grass swale and infiltration trench. The complete model consists of three interacting components: a watershed water quality simulation model (HSPF model), a reservoir water quality model (adopted CE-QUAL-W2 model) and an optimization model base on the GAlib, that is a well-developed Genetic Algorithms (GA) Software. This research takes Feitsui Reservoir for example. In the optimization model, the objective function is to minimize the total annual cost of BMPs and constraints consider water quality standards for the concentrations on phosphorus (PO4) and total suspended solid (TSS), etc. This study simulates the discharge and pollutant loading in 2002-2003. Also, the reservoir water quality model is embedded to simulate the pollutant concentration variation after the pollutant flow into Feitsui Reservoir. The model developed in the present study can be used as an efficient approach to the implementation of BMPs in the entire watershed to mitigate the impact of stormwater pollution on the receiving water bodies. The result can provide the decision makers with a clear and useful way for nonpoint pollution control and management at the watershed scale.