Abstract
The potential of canal side weirs for uniform water delivery to irrigation furrows and system flexibility is assessed. Weir discharge uniformity is affected by: (1) Canal velocity and weir entrance conditions; (2) variations in weir crest construction elevations; and (3) variations in water surface elevations along the distribution canal. For sharp‐entranced weirs, model studies show that the decrease in canal flow velocity down a typical distribution reach can result in an increase in weir discharge up to 15%. This velocity effect is significantly dampened by using a streamlined entrance to the weir. Field data on weir crest elevations have a standard deviation of about 3 mm, which translates into 6–8% weir discharge variation at normal discharge settings. A computer model of distribution canal flows indicates weir discharge uniformity is improved by shortening the length of the reach, reducing the required weir discharge setting, and increasing canal size. A design guideline is developed for the system.
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