CANAL REGULATIONS

CANAL REGULATION WORKS

1. CANAL REGULATIONS

2. CANAL REGULATION Introduction: Canal regulation is the process of regulating water from a reservoir or diversion head works through a canal system for a dependable supply of water for irrigation requirement. The canal system plays a key role in regulating the irrigation water. The major components of a permanent canal system are discussed below. Components of a permanent canal system Main canal Branch canal Distributaries Water courses

3. Components…… Main Canal (M): This canal takes off from the river and derives water through a regulator. For a certain length in the beginning the canal may be in full cutting. Obviously direct flow irrigation from such a channel is not possible as its water surface is below the general ground surface. The main function of the canal is to take the required amount of irrigation water at the head and to deliver it in the canal system below. Branch Canals (B): After the main canal comes in the tract which is to be irrigated by the canal system, water is distributed over the entire commanded area. For this purpose the main canal is branched to cover the whole area. The bifurcated canals are called branch canals or simply branches.

4. Components… From the branches also direct irrigation is very rarely done. The main function of the branches is to make the water available in different parts of the tract for further distribution. The section of a branch canal is smaller than the main canal. Distributaries: They can be subdivided into: i . Major distributaries, and ii. Minor distributaries or minors. Major Distributaries (D): They are also named Rajbaha . Major distributaries are smaller in section than the branches. They are taken off mainly from the branches to distribute the water to various parts for direct irrigation purposes.

5. Components… Sometimes major distributaries may take off directly from the main canal. The distributaries provide water to field channels through outlets for irrigation. Minor Distributaries (M): They are smaller in section than the major distributaries. The main purpose of these distributaries is to reduce the length of the field channels. They are taken off from the major distributaries and sometimes from the branch canals. When the length of the field channels is more than 3 km the minor distributaries are introduced to reduce the length. They are also called minors.

6. Components… Water Courses: They are also named as guls or field channels. They are the channels which take irrigation water to the fields. The water courses derive their supply from the distributaries through outlets. An outlet is a simple and a small irrigation structure constructed on the distributaries. It may be a simple pipe outlet or any other type provided to allow flow of water into the water courses. Irrigation department is responsible for construction and maintenance of the canal system up to minor distributaries. The field channels are constructed by cultivators themselves as per the alignment sanctioned by the department.

7. Components… Nowadays the field channels are also constructed by irrigation department for cultivators. The job of maintenance of field channels is left entirely to the cultivators. The length of a water course should not exceed 3 km in any case. It generally serves an area of 40 to 50 hectares. The upper limit of discharge in a watercourse ranges between 0.08 to 0.06 m 3 /sec.

8. Canal Regulation Works These are structures constructed to regulate the flow rate and volume of water Necessary for the efficient working and safety of an irrigation channel Important Regulators Head regulator or head sluice Cross regulator Canal outlet Regulators are normally aligned at 90 degree to weir.

9. Head Regulator Regulators Constructed at the off taking point are called head regulators. When it is constructed at the head of main canal it is known as canal head regulator. And when it is constructed at the head of distributary, it is called distributary head regulator. Function: T o cont r ol th e ent r y of water eit h er from th e rese rvoir or from the main canal. To control the entry of silt into off taking or main canal. To serve as a meter for measuring discharge of water.

10. Head Regulator Construction: The components of head regulator depends upon the size of canal and location of head regulator. It consists of one or more gated research openings with barrels running through the bank. For large canals head regulators are flumed to facilitate the measurement of discharge.

11. Head Regulator

12. Cross Regulator Cross Regulator A Regulator Constructed in the main canal or parent canal downstream of an off take canal is called cross- regulator. It is generally constructed at a distance of 9 to 12 km along the main canal and 6 to 10 km along branch canal. Functions: ( i ) To Control the flow of water in canal system (ii) To feed the off taking Canals (iii) To enable closing of the canal breaches (iv) To provide roadway for vehicular traffic

13. Cross Regulator The sill of regulation is kept little higher than the u/s bed level of canal across which it is constructed. Construction: For Cross Regulators abutments with grooves and piers are constructed parallel to the parent canal. Vertical lift gates are fitted in the grooves. The gates can be operate from the road.

14. Canal regulators

15. Canal regulators

16. Canal regulators

17. Types of Regulator Still pond regulation Open flow regulation Silt control devices

18. Still pond regulation: Canal draws water from still pond Water in excess of canal requirements is not allowed to escape under the sluice gates. Velocity of water in the pocket is very much reduced; silt is deposited in the pocket When the silt has a level about 1/2 to 1m below the crest level of Head Regulator, supply in the canal is shut off and sluice gates are opened to scour the deposited silt.

19. Open flow regulation Sluice gates are opened and allow excess of the canal requirement Top water passes into the canal Bottom water maintain certain velocity in the pocket to keep the silt to remain in suspension Canal is not closed for scouring the silt.

20. Silt Control Devices Scouring Sluices or Under sluices, silt pocket and silt excluders The above three components are employed for silt control at the head work. Divide wall creates a silt pocket. Silt excluder consists of a number under tunnels resting on the floor pocket. Top floor of the tunnel is at the level of sill of the head regulator. Various tunnels of different lengths are made. The tunnel near the head regulator is of same length of head regulator and successive tunnels towards the divide wall are short. Velocity near the silt laden water is disposed downstream through tunnels and under sluices.

21. Silt Control Devices Silt Excluder: The silt excluder is located on the u/s of diversion weir and in front of the head regulator. The object is to remove silt that has entered in the stilling basin through scouring sluices. Silt Ejector: Silt Ejector is located in the canal take off from the diversion weir at 6 to 10 km in the canal reach. It ejects the silt that has entered in the canal

22. Installing silt excluders Making entry of clear top water by Providing raised sill in the canal Lower sill level of scouring sluices Wide head regulator reduces velocity of water at intake Smooth entry to avoid unsteady flow Handling careful the regulation of weir Disturbance is kept at minimum in weirs

23. Silt excluder: Silt is excluded from water entering the canal, constructed in the bed infront of head regulator - excludes silt from water entering the canal Designed such that the top and bottom layers of flow are separated with the least possible disturbance Top water to canal - bottom, silt laden through under sluices No of tunnels resting on the floor of the pocket of different lengths The tunnel near the head regulator being of same length as that of the width of head regulator - tunnel of different length. Capacity of tunnel is about 20% of canal discharge

24. Minimum velocity 2 to 3 m/s to avoid deposition in tunnel is kept the same as sill level of head regulator From discharge and scouring velocity the total waterway required for under water tunnels can be determined Silt extractor or silt ejector: Device by which the silt, after it has entered the canal is extracted or thrown out. Constructed on the canal some distance away from head regulator Horizontal diaphragm above the canal bed anal bed slightly depressed below the diaphragm 0.5 to 2.8m

25. Under diaphragm, tunnel which extent the highly silted bottom water tunnel. There should be no disturbance of flow at the entry. Sediment - laden are diverted by curved vanes Forwards the escape chamber: steep slope to escape channel is provided. The streamlined vane passage accelerate the flow through them, thus avoiding deposition (decreasing section area increases the flow velocity) The tunnel discharge by gate at the outlet end (escape channel)

26. Location: If near head regulator, silt will be in suspension If too far away than result in silting of canal.

27. Classification of Regulators:   I –  According to purpose: 1-  Regulation of Discharge “Q” 2-  Regulation of Water slopes (and velocity) 3-  Measurement of Discharge “Q” 4-  Division or Diversion of Discharge 5-   Change in bed slope 

28. II – According to location 1-  Head Regulator 2-  Intermediate Regulator 3-  Escape Regulator 4-   Diversion Regulator   III –  According to Material (Type of Construction) 1-  Masonry Arch Regulator 2-  Mixed Type Regulator (masonry + RC)  3- RC Regulator

29. Location of regulators Should always be located at straight reaches (position “a”)  Never located within curves in waterways (either silting or scouring is liable to occur causing destruction of the regulator (position “b”) At diversion; location should be chosen 50-200m DS the point of diversion “c”   Should always be located at straight reaches (position “a”)       

30. Advantages of Regulators to   weirs   Regulator may be fully opened at flood time giving enough water way area to avoid excess heading up                                                        both US & DS water levels are controlled minimize silting at US

31. Principles of Design       Hydraulic Design To get the area of water way Discharge is considered for fully opened Regulator  Determination of heading up Check the velocity through regulator vents        

32.  Floor design To determine the floor length  To cover the floor length by regulator floor  To check the percolation length To determine the floor thickness To make adequate precautions against   undesired percolation  

33.   Structural Design To determine the dimensions and check the stability of the structural elements  which are: Piers; Abutments; wing walls Roadway (bridge); gates  Cranes and lifting devices

34. Main Elements of Regulators 1-  The water area of vents (S* dw ) 2-  The bridge 3-  The piers between the regulator vents 4-  The abutments 5-  The floor 6-  The gates 

35. Forces acting on Regulator Pu         -           Upstream water pressure PD        -           Downstream water pressure acting on the DS emergency groove PL        -           Water pressure in lateral direction when one vent is closed for repair PW       -           Wind pressure on exposed surface (if any) W1       -           Weight of bridge + live load (for worst case of loading) W2       -           Own weight of pier W3       -           Own weight of gates + lifting apparatus (if any