地下堰體對集水廊道取水影響之研究

Influence of Underground Weir on Water Withdrawal of Infiltration Gallery

劉宏仁(Hung-Jen Lin) ； 徐年盛(Nien-Sheng Hsu) ； 江崇榮(Chong-Rong Jiang) ； 朱哲廷(Che-Ting Chu)

《農業工程學報》 63卷3期 (2017/09) Pp. 50-59

https://doi.org/10.29974/JTAE.201709_63(3).0004

摘要

集水廊道為設置於河床下礫石層以汲取地下水的水工結構物，優點為水質清澈且全年可穩定取水。若於集水廊道下游建立一地下堰體，除了可避免河床過度淘刷導致集水廊道基腳沖毀並延長集水廊道的壽命外，亦可抬升集水廊道附近之地下水位，進而增加集水廊道出水量。本研究旨在探討建立地下堰體對集水廊道取水量之影響，以存在集水廊道的林邊溪二峰圳為研究區域，配合數值模式率定、成本經濟分析以進行地下堰體與集水廊道之最佳埋深優選。本研究首先利用一虛擬設計案例分別將集水廊道與地下堰體概念化，以確認利用FEMWATER 模式進行數值模擬時之邊界條件設定方式，並分別探討各種地下堰體與集水廊道配置情況下，集水廊道附近地下水位變化情況之合理性。接著蒐集林邊溪二峰圳相關資料進行集水廊道數值模式之建立與率定；再進行二峰圳集水廊道與地下堰體之成本效益分析，並將地下堰體加入模式模擬，最後分別以地下堰體與集水廊道之埋深為決策變數、最大營運淨效益為目標函數，進行下列兩組案例之分析：（1）已有二峰圳，增設地下堰體，以及（2）現地未有工程構造物，同時建立地下堰體與集水廊道。研究結果顯示地下堰體以及集水廊道之設定可合理模擬地下水位之變化情況。當二峰圳已存在時，增設地下堰體且底部埋深至地下15.2公尺時為最佳埋深；假設現地無任何構造物，同時建立地下堰體與集水廊道時，集水廊道埋深18.6公尺、地下堰體埋深21.5公尺為最佳埋深。地下堰體確實可增加集水廊道的出水量，最佳化設計與否工程效益差異可達億元以上。

關鍵字

集水廊道 ； 地下堰體 ； FEMWATER ； 二峰圳

並列摘要

Infiltration gallery is an artificial structure installed below the riverbed including perforated in gravel to collect subsurface runoff in riverbed. The main advantage of the infiltration gallery is stably supplying clean water. If we build an underground weir downstream of infiltration gallery, in addition to avoiding riverbed erosion and extend the life of the infiltration gallery, it can also raise groundwater level around the infiltration gallery and increase water-intake from infiltration gallery. The aim of the research is investigating the influence of underground weir on infiltration gallery, and focused on groundwater level and water-intake. First, this study design a simple case and conceptualize infiltration gallery and underground weir to confirm that the usability of boundary conditions set in FEMWATER numerical model, and then discusses the rationality of the variation of groundwater level around infiltration gallery by setting different configuration of infiltration gallery and underground weir. Second, this study collected observations about Er-Feng infiltration gallery to establish and calibrate a numerical model of groundwater flow. Finally, this study use the model has been calibrated to establish an optimization model. The objective of the optimization model is the maximum annual value of net benefit. The decision variables include the depth of infiltration gallery and underground weir. The results shows: (1) By a virtual case study results that this study combined FEMWATER mode, underground weir and infiltration gallery boundary conditions setting can be reasonably simulated groundwater level changes; (2) When Er-Feng infiltration gallery has built, the optimal depth of weir is 15.2m. If there is no structure in the wild, the optimal depth of infiltration gallery and underground is 18.6m and 21.5m. Underground weir can indeed increase water-intake from infiltration gallery. Both facilities need to be optimally designed, since the difference of benefit among different design can be over billion dollars.

並列關鍵字

Infiltration gallery ； Underground weir ； FEMWATER ； Er-Feng irrigation system