Canal alignment

This presentation covers about what is meant by canal, types of canal alignment, factors to be considered for canal alignment

1. CANAL ALIGNMENT

2. Content: Definition of canal Canal Alignment Contour Canal Watershed Canal Side slope Canal General considerations for Alignment Canal lining

3. DEFINITION OF CANAL: A canal is an artificial channel , generally trapezoidal in shape constructed on the ground to carry water to the fields either from the river or from a tank or reservoir.

4. CANAL ALIGNMENT: A canal has to be aligned in such a way that it covers the entire area proposed to be irrigated, with shortest possible length and at the same time its cost including cost of drainage works is a minimum.

5. Types of canal Alignment: Ridge / watershed Canal Contour Canal Side slope Canal

6. RIDGE CANAL : The dividing ridge line between the catchment areas of two streams (drains) is called the watershed or ridge canal. It is suitable for plain areas , where slopes are relatively flat and uniform This type alignment ensures gravity irrigation on both sides of the canal.

7. Advantages: This canal supply water on both side and thus large area may be taken under cultivation. It is the best irrigation canal and most economical Disadvantages: Suitable only for plain area not for hilly area.

8. Contour Canal: Canal aligned nearly parallel to the contour line is called contour canal They are aligned generally when canals take off from river. Culturable area lies on one side of it. as one of banks on the higher side. Sometime it is called single bank canal. .

9. Disadvantages : It can only irrigate one side. Advantages: Low initial cost. Discharge capacity increases as rain water from higher side is collected in the canal

10. SIDE SLOPE CANAL: A side slope canal is that which is aligned at right angles to the contours; i.e. along the side slopes. It is a canal which is aligned roughly at right angle to contours of the country but not on watershed or valley. The canal thus runs roughly parallel to the natural drainage of the country and as such cross drainage works are avoided.

11. Advantages: Construction of cross drainage work is not necessary. Disadvantages: It can irrigate only one side. Slope is more if it is unlined canal erosion will takes place.

12. Factors to be considered during canal alignment: It should serve the entire area proposed to be irrigated. Cost of construction including cross drainage works should be minimized. Where canal crosses valleys, different types of cross drainage works are required. There should be Consideration of economy in alignment of contour canals.

13. All possible alignments should be studied and the best suited alignment should be selected. Number of rinks and acute curves should be minimized. They should be aligned as far as possible in partial cutting partial filling. Deep cutting should be avoided by comparing the overall cost of alternative alignments. Reduce the maximum length and slope. Canal have to be lined to avoid seepage.

14. Necessity of Canal Lining: Maximum velocity limited to prevent erosion Seepage of water into the ground Possibility of vegetation growth in banks, leading to increased friction Possibility of bank failure, either due to erosion or activities of burrowing animals To avoid water logging To avoid movement of contaminated groundwater To avoid piping through and under channel banks.

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