灌溉渠道流量比測暨水力特性研究

流量資料向為水資源規劃、防災預警模式所需之基本。以往，流量觀測多以侵入式觀測設備，搭配重錘進行流量觀測；近年，聲波督普勒流速儀（acoustic Dopplercurrent profiler，簡稱ADCP）已被運用為河川或灌溉排水渠道之流量觀測。ADCP 雖可同時測得流速剖面分佈及河川斷面，惟，在近液面處及近底床處仍有盲區，其盲區之流速推估仍有待進一步研究釐清更佳流速分佈式外延推估之適用性。據此，本研究擇定嘉南大圳分岐站北幹渠為流量比測站址，以傳統旋杯式流速儀之流速儀之流速觀測資料為基準，復以ADCP至可觀測區之流速資料搭配邱式理論及冪次律，探討流速外延之合理性。結果顯示，邱氏理論及冪次律流速外延後之流量估算平均誤差小於3%，可達到合理流量計算精度。最後，本研究建立嘉南大圳分岐站北幹渠之水位流量關係式，可供嘉南農田水利會參考。

關鍵字

流量；盲區流速外延；邱氏理論；冪次律；聲波督普勒流速儀

並列摘要

Flow discharge measurements are an essential component of water resources planning and hydraulic model validation for the purpose of disaster prevention. In the past, the flow measurements were conducted by using intrusive instruments, such as propeller-type current meter with sounding weight. Recently, the acoustic Doppler current profiler (ADCP) has been widely used for the discharge measurement in natural rivers and irrigation channels. Although the ADCP can measure the velocity profile and cross section, however, near the water surface and river bed, still having un-measured zones. The extrapolation of velocity profile for the un-measured zone still needs more investigation. To better understand the velocity profile extrapolation phenomenon, this study investigates the comparison of discharge measurement in an irrigation channel. The field site was chosen in the North channel of Fen-Qi Station of Taiwan Chia-Nan Irrigation Association. The velocity measured by the cup-type propeller current meter was used for the benchmark. The velocity measured by the ADCP was extrapolated by using Chiu’s method and Power law for the velocity comparison. The results show that error of the estimated discharge is less than 3% either by using Chiu's method or Power Law for the velocity extrapolation. Finally, to provide hydrological authorities with a rational method to estimate discharge, a discharge rating curve (stage-discharge relationship) was proposed.

並列關鍵字

Discharge ； Velocity extrapolation Chiu's method ； Power Law ； Acoustic Doppler current profilers

國際替代計量

灌溉渠道流量比測暨水力特性研究

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