集水區非點源污染最佳管理作業最佳配置策略之研究

Optimal Best Management Practices (BMPs) placement strategies for nonpoint source pollution control at a watershed scale

謝斌暉(Pin-Hui Hsieh)

指導教授 ： 郭振泰

國立臺灣大學/工學院/土木工程學研究所/博士(2007年)

https://doi.org/10.6342/NTU.2007.03258

摘要

本研究的目的在以集水區為尺度建立一個最佳管理作業的最佳配置模式。模式包括三個互動的單元：集水區暴雨模式（本研究採用VAST 及BASINS 模式）、零維水庫水質模式（非穩態、時變性的Vollenweider 模式）及一個最佳化模式（遺傳演算法，GAs）。
本研究三個主要任務為：1.暴雨期間集水區水文及水質的影響；2.發展一個可信賴、有效率的最佳化模式整合最佳化工具與水庫水質模式，來尋找最佳管理策略系統的最佳配置方式；3.考量總懸浮固體物及總磷濃度，且有三種最佳管理作業納入模式中。
本研究發展一個後處理程式，包括：最佳管理作業模擬、河道演算、水庫水質模式及遺傳演算法等。集水區暴雨模式的結果，如VAST 及BASINS 的流量與污染物濃度，被當成一個反應矩陣。程式測試的結果發現單一小的暴雨並沒有對水庫水質產生嚴重的影響，換句話說在此狀況下不需要任何最佳管理作業。程式可以依據不同的染色體數量在被接受的時間內找到最佳解。經由調整不同的污染物濃度限制式，本研究分析三種不同的水質情況。總磷濃度必須滿足貧養、中養與優養的水質；同時，總懸浮固體物濃度必須控制在25 ppm 以下。
真實降雨事件發生在03/28/2003-04/14/2003 及 2002 至2003 年間分別被用來檢定與驗證VAST 與BASINS 模式。模擬的結果顯示VAST 與BASINS 模式在翡翠水庫集水區是好用的暴雨分析工具。縱使非穩態、時變性的Vollenweider 模式僅有一個污染物沈降速率，我們採用2002 年台北翡翠水庫管理局的總懸浮固體物與總磷濃度的變化與模式模擬結果做比對，其結果亦相當良好。
本研究共分析三種時間尺度的情況，包括：短期、長期及單一設計暴雨等。其中，以設計暴雨的結果每年需要投入最多的經費，因為2 年/2 小時、5 年/4 小時是謝等人（2003 年）找到的最強的暴雨能夠對水體水質產生最大的衝擊。在1988 到2004 年間，2002 年是最乾旱的一年，分析所得的所需年經費亦相對較小。
本研究所搜尋到的接近最佳解也與翡翠水庫集水區最佳管理作業配置的相關研究做比較，並採用他們的配置最為搜尋前的初始染色體。本研究採用的尖峰濃度限制較前人因為簡化的需要所用的平均濃度要大；但由於非穩態的優勢能顯現出真實暴雨污染物的傳輸現象，本研究能找到比前人研究更經濟省錢的最佳管理作業配置方式。決策者或設計者可以採用本研究所得的最佳管理作業配置方式，並應充分瞭解最佳管理作業的一些限制，如果有地形或用地取得不易等因素，許多如范與張（2006 年）建議的非結構性最佳管理作業也可以用來當作另一個非點源污染控制的選擇。

關鍵字

最佳配置策略水區暴雨模式 ； 最佳管理作業模擬 ； 河道演算 ； 水庫水質模

並列摘要

The purpose of this study is to establish an optimization model for the optimalplacement of structural Best Management Practices (BMPs) at the watershed scale. It consists of three interacting components, i.e. a watershed stormwater simulation model(VAST/BASINS), a zero-dimensional reservoir water quality model (unsteady, time variable Vollenweider model), and an optimization module (the genetic algorithms, GAs). Three major tasks are completed in this work: 1) the investigation of how the watershed hydrology and water quality is affected during the storm period; 2) develop a reliable and effective
optimization framework coupling the optimization tool and the reservoir water quality model to explore the optimal placement strategies of BMPs system; and 3) Both total suspended solids (TSS) and total phosphorus (TP) are taking into account and three kinds of BMPs are
considered.
A post treatment program is developed which combines BMPs simulation, channel routing, reservoir water quality models and GAs. The results analyzed by watershed stormwater models, such as VAST and BASINS models, are taken as a response matrix. The program test results show that a single small storm does not cause significant effect on the reservoir water quality, i.e. no BMPs is required under such situation. The program also finds
the optimal solutions in an acceptable time depending on the chromosome population. By changing the pollution concentrations in the constraints, three scenarios are analyzed in this study. The TP concentrations should satisfy oligotrophic, mesotrophic and eutrophic
conditions while the TSS concentrations should be kept below 25 mg/l at the same time.
Real storm events during 03/28/2003-04/14/2003 and 2002-2003 are adopted to calibrate and validate VAST and BASINS models respectively. The modeling results demonstrate thatVAST and BASINS are good stormwater analyzing tools in Fei-Tsui Reservoir watershed.
Although there is a pollutant settling rate in the unsteady, time variable Vollenweider model, the TSS and TP concentration variations in 2002 are also compared with the field data observed by Taipei Fei-Tsui Reservoir Bureau.
There are three different time scale scenarios analyzed in this study, they are short term, long term and single design storm. The results analyzed by design storms cost much more money than the other two. Because the 2-year/ 2-hour and 5-year/ 4-hour storms are the critical storms found by Hsieh et al. (2003) that cause the serious damages on the water body. During 1988 to 2004, the 2002 is the driest year so that the annual costs analyzed by the
program are relatively smaller. The near optimal solutions found in this study are compared with former research in
Fei-Tsui Reservoir watershed. This study also uses their placement strategies as one of the initial chromosome. The peak pollutant concentrations are larger than the averaged values they used in former studies. Due to the advantage of unsteady state model, more economical placement strategies are found and suggested in this study. The decision makers or designers can adapt the BMPs placement strategies found in this study and should be good at the
limitations of BMPs. Several non-structural BMPs proposed by Fan and Chang (2006) in Fei-Tsui Reservoir watershed can be good alternatives for nonpoint source pollution control when there are topographic and land ownership problems in the future.

並列關鍵字

Optimal placement strategy ； Watershed stormwater model ； Best management practice model ； Channel routing ； Reservpor water quality model ； Genetic algorithm

參考文獻

Zhai, Y. Y. (2004), Applying the WinVAST model for Best Management Practice (BMP) Placement Optimization, dissertation of master degree, Department of Civil Engineering, University of Virginia.

Chang, C. L. (2005), Applying fuzzy theory to analyze spatial rainfall variability for estimating runoff and non-point source pollution, Doctoral Dissertation, Graduate Institute of Environmental Engineering, National Taiwan University, Taiwan. (in Chinese)

Kuo, J. T., Hsu, N. S., Chen, Y. C. and Wu, M. C. (2006c), Assimilative Capacity Estimation for the Catchment Protected by the Taipei Water Management Office, sponsored by Taipei Water Management Office, Water Resources Agency, Ministry of Economic Affairs, MOEAWRA0950103. (in Chinese)

Kuo, J. T., Cheng, W. C. and Chen, L. (2002), “Multiobjective water resource systems analysis using genetic algorithm- application to Chou-Shui River Basin”, Proceedings of Watershed & River Basin Management Conference, Edinburgh, 11-13th, Sept., 2002.

Chiu, S. K. (2004), Optimal BMPs placement-Application to Fei-Tsui Reservoir watershed, Dissertation of master’s degree, Department of Civil Engineering, National Taiwan University, Taiwan. (in Chinese)