slope effect on discharge efficiency in rectangular broad crested weir with sloped upstream face

the rectangular broad crested weirs are widely used to measure the water dischargewhich is one of the most popular tools in the irrigation canals particularly, in developingcountries.the present article is trying to demonstrate the results of an experimental work carriedout on rectangular broad crested weir with sloped upstream face to investigate the effect ofupstream slope on discharge efficiency. the upstream slope was varying from 90 to 23 degreeswhile incoming discharge was ranging from 14 to 75 lit/ sec. the experiments were conducted in aflume with a weir of fixed height under the normal downstream water depth .it is revealed that theslope of upstream face in rectangular broad crested weir would smoothen the flow profile havingthe critical depth on the weir crest adjacent and upstream of downstream edge of the weir . theresults also lead to a novel achievement showing that the weir discharge efficiency is dependenton the slope of upstream face of the weir. as the slope of upstream face of the rectangular broadcrested weir is decreasing from 90 to 23 the weir discharge efficiency is increasing and reachingto its maximum through a parabola function at slope angle of 25 degrees(i.e. 1:2.15). theinvestigation also showed that the depth of flow over the weir crest, the specific energy head ofthe approaching flow relative to chanel bed and the critical depth would be a pertinent similarityscales to asses the flow behavior over different sloped rectangular broad crested weirs betweenmodel and prototype. however, some broad investigation is recommended to endorse theachievements.