Paddy and Water Environment

, Volume 12, Issue 1, pp 203-212

First online:

Velocity distribution and discharge calculation at a sharp-crested weir

  • Shun-Chung TsungAffiliated withTaiwan Typhoon and Flood Research Institute Email author 
  • , Jihn-Sung LaiAffiliated withHydrotech Research Institute, National Taiwan University
  • , Der-Liang YoungAffiliated withDepartment of Civil Engineering, National Taiwan University

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A sharp-crested weir in open channel is a useful device to calculate discharge via head-discharge relationship. However, water stage measurement site and discharge coefficient significantly influence discharge calculation accuracy. Therefore, this study measures and simulates velocity distribution at the weir section using 16-MHz MicroADV and FLOW-3D, respectively. The water depth and surface velocity at the weir section are selected to characterize velocity distribution using gamma probability density function. In this study, accurate discharge is calculated by velocity–area integration method based on velocity distribution derived from measured water depth and surface velocity. The main contributions of this study are to give an exact measurement site, link velocity distribution and discharge, avoid discharge coefficient influence, and improve discharge calculation accuracy.


Sharp-crested weir Velocity distribution Surface velocity Crest Froude number