Discharge estimation in lined irrigation canals by using surface velocity radar
2018
Chen, Yen-Chang | Liao, Yi-Jiun | Chen, Wei-Lun
This study proposes a surface velocity method for discharge estimation in lined irrigation canals. In this method, a surface velocity radar is used for surface velocity measurement. However, this radar cannot be used to obtain a point velocity on the water surface. A velocity profiler is used to measure the velocity distribution in the cross section of a canal. The measured data are used to obtain surface and mean velocities in verticals by applying a probabilistic velocity distribution equation. Subsequently, the linear relationship between the surface velocity measured by the surface velocity radar and the surface velocity estimated by the velocity distribution equation can be established. Additionally, the relationship between the estimated surface velocity and mean velocity in verticals can be obtained through linear regression; this relationship is a constant. Therefore, these two relationships can be used to derive a surface velocity coefficient for converting surface velocity to mean velocity in a vertical. The surface velocity coefficient used in lined irrigation canals is different from that used in natural streams. It is not constant and varies with the surface velocity observed by the radar. The feasibility of the proposed method is tested by conducting discharge estimation processes in five lined irrigation canals. The results show that the proposed method is reliable and accurate for estimating discharge in lined irrigation canals.
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