Effect of Crest Width on Discharge Measurement Using Triangular Notch

Measurement of flow is an important factor in any water resources project development, mainly in case of irrigation channels. In irrigation system while assessing the command area and the quantity of water reaching the last point is need to be measured at various locations along the channel considering the various losses such as evaporation, evaporate-transpiration, seepage etc. Generally, for this purpose weirs are constructed at different changes to ensure the discharge. The actual discharge was measured on a Rehbock weir on the downstream of the flume. The experimental results have indicated that as the head over weir and crest width increases, the coefficient of discharge is decreasing, which may be due to the increase in friction along the crest. The frictional losses are not considered in the present study. It is further recommended that a detailed investigation is to be carried out by repeating the experiments with due consideration to frictional effects and comparing results with weirs fabricated with materials of minimal friction.