本文研究目的在於探討攔河堰引水對河川自然流量變化的影響及河川生態流量對供水穩定度與河川保護目標間之影響。本文以變異範圍法(Range of Variability Approach，RVA)中的32個水文改變指標(Indicator of Hydrologic Alteration，IHA)來評估河川流量特性受攔河堰引水之影響。由於攔河堰引水及維持河川自然流量變化是相互衝突的目標，本文分別以缺水率及整體水文改變度代表攔河堰引水的效率及維持河川自然流量變化的目標，而以多標的優選模式中的非優勢排列遺傳演算法(non-dominated sorting genetic algorithm II，NSGA-II)求解最佳解。本文將所建議方法應用於位於台灣中部濁水溪中游的集集攔河堰，首先以建堰前未受影響之天然流量建立評估標準，而後以攔河堰模擬模式演算引水後之河川剩餘流量，並據以評估其缺水率及水文改變度，而本文所考慮河川生態流量保留方式有定值、半年變化、季變化及月變化四種，演算結果顯示本文所建議的方法可以有效量化評估攔河堰供水的風險及對河川自然流量變化的影響幅度。 This study aims to evaluate the impacts on natural flow variability caused by flow diversions. Restoration of altered hydrologic regimes and the associated effects on water-supply reliability by instream flow releases are also explored. This study employs the Range of Variability Approach (RVA) to quantitatively assess alterations of the natural flow variability. Thirty-two hydrologic parameters, called Indicators of Hydrologic Alteration (IHA), associated with the degree of hydrologic alteration are used to assess the hydrologic alteration of streamflows. Since water-supply reliability and sustaining natural flow variability are conflicting, the multiobjective optimization model is needed to solve these conflicting objectives in weir operation problem. Shortage ratio is used to evaluate the operation performance of the water-supply weir. The resulting degrees of hydrologic alterations for 32 IHAs are combined into a single index, called the overall degree of hydrologic alteration, to represent sustention natural flow variability objective. The non-dominated sorting genetic algorithm II (NSGA-II) is adopted in this study to solve the multiobjective weir operation problem. The proposed methodology is applying to Chi-Chi diversion weir, which is located at the midstream of the Chou-Shui River, Taiwan. The daily flow records prior to weir construction from 1951 to 1993 are used to establish RVA targets. A weir operation simulation model is established to derive the post-diversion flows for various operating schemes. In this study, various operating schemes, including constant, semi-annually varying, quarterly varying, and monthly varying instream flow release, are evaluated to determine corresponding impacts on shortage ratio and hydrologic alteration. The methodology proposed in this study could serve as a useful quantitative evaluation tool for the decision makers of the water-supply systems.
第十五屆水利工程研討會論文集=Proceedings of the 15th Hydraulic Engineering Conference，8頁