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Irrigation (81-100)

Updated: Apr 10, 2020

81. The discharge passing over an ogee spillway is given by

where, L is effective length of spillway crest and H is the total head over the

spillway crest including velocity head.


82. Coefficient of discharge of an ogee spill way depends on depth of approach and upstream slope , depends on downstream apron interference and downstream submergence


83. Which of the following spillways is least suitable for an earthen dam ?

ogee spillway


84. In case of non-availability of space due to topography, the most suitable

spillway is shaft spillway


85. In a chute spillway, the flow is usually super critical


86 For the upstream face of an earthen dam, the most adverse condition for stability of slope is sudden drawdown


87. If there are two canals taking off from each flank of a river, then there will be

two divide walls and two undersluices


88. Generally the weir is aligned at right angles to the direction of the main river

current because it ensures less length of the weir , it gives better discharging capacity ,it is economical


89. The main function of a divide wall is to separate the undersluices from weir



90. A divide wall is provided at right angle to the axis of weir


91. As compared to crest of the normal portion of the weir, the crest of the under

sluice portion of weir is kept at lower level


92. Silt excluders are constructed on the river bed upstream of head regulator


93. If h is the-'ordinate of hydraulic gradient line above the top of the floor and G is

specific gravity of floor material, then the thickness of floor is given by the formula



94. According to Khosla's theory, the exit gradient in the absence of a downstream cutoff is infinity


95. The minimum size of stone that will remain at rest in a channel of longitudinal

slope S and hydraulic mean depth R is given by 11 RS


96. The ratio of average values of shear stresses produced on the bed and the banks of a channel due to flowing water is greater than 1


97. If the critical shear stress of a channel is Τc, then the average value of shear stress required to move the grain on the bank is 0.75 Τc


98. A water shed canal avoids the cross drainage works


99.A canal which is aligned at right angles to the contour is called side slope canal


100.Garret's diagrams are based on Kennedy's theory

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