Generalised stage–discharge relationship for rectangular weirs

Abstract

Rectangular weirs, which are very common hydraulic structures used in irrigation channels as water measuring devices, can be used for measuring very small discharges as well as high flow rates. From a practical point of view, the availability of a unique stage–discharge formula that can be applied to different types of rectangular weirs would be of great practical importance. In this paper, Buckingham's theorem of dimensional analysis and the self-similarity theory are used to deduce the stage–discharge curves of different kinds of rectangular weirs such as slit and partially contracted weirs. The proposed formula is then calibrated using measurements from this investigation and experimental data from the literature. Compared with the available stage–discharge relationships, the results indicate that the proposed method can be used for the entire range of the ratio of weir width to channel width (i.e. both slit and partially contracted weirs) with acceptable accuracy.