Cross Drainage works types and its properties.pptx

cross drainage work on the super passage aqueduct canal syphon

1. Irrigation engineering CHAPTER Cross Drainage Works

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3. Humble Request

4. Also called as Drainage crossing. Cross drainage work is a structure constructed at the crossing of canal and drain, such that drain water is disposed off and canal supply is not interrupted. Unavoidable in any canal system , but costly hence should be avoided as far as possible by. Diverting on drain into an other . Changing alignment of canal such that it crosses below junction of two drains. At CDW canal is generally taken above or below drain, but in some cases both can be at same level. Note : Drain= Any natural Stream or river.

5. To minimise CDW’s , canals are aligned along Ridge line ( Watershed line) . Once canal reaches Watershed line, no CDW are required , unless canal alignment is changed for some distance. But when canal takes off from river and reaches watershed line it has to cross number of drains. At these crossings CDW’s are to be constructed as C1,C2,C3 & C4. Note: Watershed canal crosses min. no. of drains hence preferred over contour canal which crosses max. no. of drains.

6. Depending on relative bed levels & water level of canal and drain, and their relative discharge, CDW’s are of following types. Canal over Drain- Aqueduct or Syphon-aqueduct. Canal below Drain- Super passage or Canal Syphon ( Syphon). Darin through Canal- level Crossing ; Inlets or Inlets & outlets.

7. Aqueduct

8. Aqueduct Hydraulic structure in which canal is taken over drain, when bed level of canal is sufficiently above HFL of drain. Darin water flows under gravity (at atmospheric pressure) below canal as there is sufficient headway between HFL of drain and bed of canal.

9. Syphon Aqueduct Hydraulic structure in which canal is taken over drain, when bed level of canal is below HFL of drain. Canal water flows at atmospheric pressure. Drain water passes under syphonic action (pipe flow) as drain water can not pass clearly. Bed of drain is depressed below its normal bed level.

10. Super passage Hydraulic structure in which drain is taken over canal, when the bed level of drain is sufficiently above FSL of canal. Note : Opposite of Aqueduct. Canal water flows freely under action of gravity (at atmospheric pressure) below drain as there is sufficient headway between FSL of drain & bed of drain. Drain water flows in a trough supported over piers constructed over canal bed .

11. Canal Syphon ( Syphon ) Hydraulic structure in which drain is taken over canal, when the bed level of drain is below FSL of canal. Note : Opposite of Syphon Aqueduct. Drain water flows at atmospheric pressure. Canal is passed under syphonic action (or pipe flow).Bed of canal is lowered.

12. Level Crossing Hydraulic structure in which drain water is passed into canal and then taken out at opposite bank, when large canal and huge drain approach each other at same level. A level crossing consist of Crest Wall: Provided across drainage just at u/s of crossing point. Top level of crest wall is kept at FSL of canal. Drainage Regulator: Provided across drainage just at d/s of crossing point. Regulator consists of adjustable shutters at different tiers to control discharge passing into drain. Canal Regulator: Provided across canal just at d/s of crossing point. Regulator also consists of adjustable shutters at different tiers to control discharge passing into canal .

13. Level Crossing Note : Sometimes a regulator is also provided across incoming canal just at u/s of crossing point. When drain is not carrying any water, drain regulator is closed and cross regulator of canal is kept fully open so that canal flows without any interruption. When drain is carrying water , it spills over crest into canal and corresponding discharge is passed through drain regulator into drain. In this arrangement , perennial discharge of drain is used to increase canal supplies. Note : Level crossings are suitable for canals of all sizes. But they are best suitable for crossing of very large drain & canal i.e. when cost of other CDW’s would be very high.

14. Inlets or Inlets & Outlets Inlet is used to pass drain water in canal. Inlet is an open cut or a pipe in a canal bank , with bed and sides are pitched (protected) for a certain distance u/s & d/s. Outlet is used to pass drain water from canal to some near by drain. Outlet is also an open cut or a pipe in a canal bank , with bed and sides are pitched (protected) for a certain distance u/s & d/

15. Q-If the path of an irrigation canal is below the level of a natural stream, the type of cross-drainage structure provided is (a) Aqueduct (b) Super passage (c) Sluice gate (d) Level crossing

16. Q- Super passage is a canal cross-drainage structure in which (a) canal water flows under pressure below a natural stream (b) natural stream water flows under pressure below a canal. (c) natural stream water flows with free surface below a canal (d) canal water flows with free surface below a natural stream

17. Q- What type of cross drainage work is provided when the canal runs below the drain, with FSL of canal well below the bed of the drain? (a) Aqueduct (c) Level crossing (b) Super passage (d) Siphon aqueduct

18. Q- Consider the following statements: An aqueduct is a cross drainage work in which 1. a canal is carried over the drainage channel 2 a drainage channel is carried over the canal 3. both drainage channel and canal are at the same level. Which of the statements given above is/are correct? (a) 1 only (b) 1 and 2 only (c) 2 and 3 only (d) 1, 2 and 3

19. Q- In a syphon aqueduct, the most severe condition of uplift on the floor occurs when (a) the canal and drainage run full (b) the canal runs full; the drainage channel is dry, and the water table is at the stream bed. (c) the canal is dry, the drainage floor is at HFL, and the water table is at the HFL of the drainage flow (d) the canal runs full; and the drainage is dry

20. Q- The following data pertain to a natural drain crossing an irrigation canal : Which one of the following types of cross-drainage should be recommended in this case? (a) Aqueduct (b) Syphon aqueduct (c) Syphon (d) Superpassage

21. Q-The worst condition of uplift on the flood of a siphon aqueduct occurs when there is (a) High flood flow in the drainage with canal dry (b) Full supply flow in the canal with drainage dry (c) High flood flow in the drainage with canal running full (d) Water table is at drainage bed and canal is dry

22. Q-The worst condition of uplift on the flood of a siphon aqueduct occurs when there is (a) High flood flow in the drainage with canal dry (b) Full supply flow in the canal with drainage dry (c) High flood flow in the drainage with canal running full (d) Water table is at drainage bed and canal is dry