Canal outlets and modules

Irrigation Engineering

1. Canal outlets Or Modules By : Bhalinder Singh ( INDIA )

2. Definition: Canal outlet is a device through which water is released from a distributing channel into a water course.

3. Requirement: Structurally strong With out any moving parts Difficult for the cultivators to interfere and if so easily detectable Work efficiently for small working heads Can draw fair share of silt and economical.

4. Classification of Outlets: Non modular outlets Semi modular outlets Modular outlets

5. Non-Modular outlets: These outlets operate in such a way that the flow passing through them is a function of the difference in water levels of the distributing channel and the watercourse.

6. Semi-modular outlets : The discharge through these outlets depend on the water level of the distributing channel but is independent of the water level in the watercourse so long as the minimum working head required for their working is available.

7. Module outlets: The discharge through modular outlets is independent of the water levels in the distributing channel and the watercourse, within reasonable working limits. This type of outlets may or may not be equipped with moving parts.

8. SOME OTHER IMPORTANT DEFINITIONS MINIMUM MODULAR HEAD EFFICIENCY OF AN OUTLET DROWNING RATIO MODULAR LIMIT MODULAR RANGE

9. 1. TYPES OF NON-MODULAR OUTLET OPEN SLUICE : Rectangular pucca opening created along the bank of distributary by raising two abutments.

10. Flow over upper part of section q 1 =(2/3)C d1 (2g )½ .B(H L ) 3/2 Flow through remaining lower part q 2 =C d 2 .B .(H-H L ).(2g.H L ) ½ DISCHARGE THROUGH OPENING GIVEN BY SUPRESSED WEIR

11. TYPES OF NON-MODULAR OUTLET SUBMERGED PIPE OUTLET: Generally embedded in concrete & fixed horizontally at right angles to direction of flow.

12. INCLINED PIPE OUTLET: A pipe outlet may also be designed as a semi-modular outlet, that is, one which does not depend upon the water level in the watercourse by allowing it to fall freely in to the watercourse.

13. CALCULATION OF Q FOR PIPE OUTLETS: Discharge through the pipe outlet is given by the formula: Q = CA (2gH) ½ Q is the discharge; A is the cross sectional area; g is the acceleration due to gravity; H is difference in water levels of supply channel and watercourse and C is the coefficient of discharge which depends upon friction factor (f), length (L) and diameter of the outlet pipe (d) related by the formula: The coefficient f is the fluid friction factor and its value may be taken as 0.005 and 0.01 for clear and encrusted iron pipes respectively.

14. 2. TYPES OF SEMI-MODULES PIPE OUTLET DISCHARGING FREELY INTO AIR VENTURI FLUME OULET OR KENNEDY GUAGE OUTLET OPEN FLUME OUTLET ADJUSTABLE ORIFICE SEMI-MODULE

15. TYPES OF SEMI-MODULES PIPE OUTLET DISCHARGING FREELY INTO AIR: Oldest type of flexible outlet. The discharge depends only on water level of distributary. Silt Conduction Is quite Good. Efficiency is High.

16. TYPES OF SEMI-MODULES VENTURI FLUME OULET: Become obsolete these days. It is an old one & designed by Kennedy in 1906{PUNJAB}

17. TYPES OF SEMI-MODULES OPEN FLUME OUTLET : This is a smooth weir with a throat constricted sufficiently long to ensure that the controlling section remains with in the parallel throat for all discharges up to the maximum.

18. CALCULATION OF Q FOR OPEN FLUME OUTLET Q = C B t H 3/2 Where Q is related to the coefficient of discharge, C, as given in the table below; Bt is the width of the throat in cm; and H is the height of the full supply level of the supply channel above the crest level of the outlet in cm.

19. TYPES OF SEMI-MODULES ADJUSTABLE ORIFICE SEMI-MODULE:

20. CALCUALTION OF Q FOR APM The discharge formula for this type of weir is given as: Q = C B t H 1 (H 2 ) 1/2 Where Q is related to the coefficient of discharge, C, which is taken equal to around 0.0403; Bt is the width of the throat in cm; H 1 is the depth of head available, that is the difference between the supply channel full supply level and the outlet bed (crest) level; and H 2 is the difference between the supply channel full supply level and the bottom level of the roof block

21. 3. TYPES OF RIGID MODULES GIBB’S MODULE KHANNA’S RIGID MODULE FOOTE MODULE

22. TYPES OF RIGID MODULES GIBB’S MODULE: DESIGNED BY A.S.GIBB{Punjab Irrigation Dept.} Q Varies b/w 0.03 to 0.45 cumec For lower value of Q b/w 1 to 3 cusecs, it is economical in RCC structure For higher value of Q , it is constructed in brick masonry.

23. THANK YOU ALL