Application of Water Quality Model to Determine Minimum Instream Flow for Fish Survival
Date Issued
2004
Date
2004
Author(s)
Liu, Shin-Yi
DOI
zh-TW
Abstract
淡水河流經台北市區，接收大量之廢污水。而其支流新店溪下游屬感潮河段，其溶氧量普遍偏低。特別是洶纁伝薄A上游之翡翠水庫、青潭堰與直潭壩蓄水以提供大台北地區之民生用水，常使新店溪河水之溶氧不足，並造成魚類暴斃。
本研究之目的在於應用數值模式模擬淡水河系水理與水質之動態變化，且著重於新店溪之部分詳加探討。模式使用西元2000年之地形資料進行檢定。水理部分於淡水河系上選定若干測站，將測站之模擬值與實測水位、流速資料相比較以完成驗證工作。水質方面則以環保署於淡水河系上所量測之實測資料為基準進行檢定與驗證，並推估相關之點源與非點源污染量。所模擬之水質變數主要為氮、磷、生化需氧量以及溶氧。
本研究中以每月之Q90與Q75設計流量模擬，證實洶臙薑壯C流量確實造成魚類生存之危機。建議翡翠水庫、青潭堰與直潭壩應利用豐水期蓄水，洶臙薇挴雪s店溪至Q75之調節水量，並配合點源污染量之削減，則可成打ㄓ氻蠐擗仄赫鞢A使之滿足魚類生存條件而不導致魚類因溶氧不足而死亡。
The Hsintien Stream is one of the major branches of the Danshuei River system, which runs through the metropolitan capital city of Taipei and receives large amount of wastewater. The dissolved oxygen is generally low in the tidal portion of the Hsintien Stream. Hypoxia/anoxia occurs often, particularly during the low flow period when the Feitsui Reservoir, Chingtan Dam and Chihtan Dam impound the freshwater for municipal water supply. Fish kills happen from time to time.
The purpose of this study is to apply a numerical hydrodynamic and water quality model to the Danshuei River, with special attention to the tidal portion of the Hsintien Stream. The model is calibrated with the prototype conditions of the year 2000. The hydrodynamic portion of the model is recalibrated with measured surface elevation and velocity at various stations in the river system. The water quality portion of the model is calibrated with respect to the field data provided by Taiwan EPA. We also estimate the related input data of point and nonpoint sources. The model can simulate the concentrations of various forms of nutrients, CBOD and dissolved oxygen.
In this study, we use the design monthly flow of Q90 and Q75 to demonstrate that the low flow does result in low DO conditions endangering the fish survival. The model simulation results suggest that the conditions may be mitigated by the combination of pollutant reduction and flow augmentation. If the point source loading is reduced by 75%, then the maintenance of Q75 flow in the Hsintien Stream will ensure DO higher than 1 mg/L. The Feitsui Reservoir, Chingtan Dam and Chihtan Dam may impound water during the flood periods and release some to maintain Q75 flow in Hsintien Stream during the drought periods.
Subjects
魚類存活
新店溪
模式檢定與驗證
溶氧
水質模擬
fish survival
Hsintien Stream
model calibration and verification
water quality simulation
dissolved oxygen
Type
thesis
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