Match the following types of canals with their types of alignment. Type of Canal Type of Alignment A. Ridge canal 1. Aligned roughly at right angles to the contours B. Contour canal 2. Aligned along the watershed C. Side slope canal 3. Aligned nearly parallel to the contours
A - 2, B - 3, C - 1
Understanding Canal Alignment Types
Canal alignment refers to the path a canal follows relative to the ground topography, specifically the contours of the land. The choice of alignment significantly impacts the cost of construction, the area that can be irrigated, and the requirement for cross drainage structures.
Exploring Different Canal Alignments
There are three main types of canal alignments:
- Ridge Canal: This type of canal is aligned along the watershed line (the highest point of the area). Following the ridge allows the canal to irrigate land on both sides. Because it follows the highest ground, it generally does not intercept natural drainage lines, minimizing the need for costly cross drainage works.
- Contour Canal: A contour canal runs roughly parallel to the contours of the ground. This alignment is typically chosen to minimize excavation and filling costs as the canal bed maintains a relatively constant elevation. However, being on the side of a ridge, it can only irrigate land on one side (the lower side) and will intersect with natural drainage lines flowing from the watershed, requiring numerous cross drainage structures.
- Side Slope Canal: This canal is aligned on the side slope of the ground, running roughly perpendicular or at right angles to the contours. Side slope canals are common in hilly or undulating terrain. They generally do not intercept natural drainage lines flowing down the slope, thus avoiding the need for cross drainage works. Construction on steep side slopes can be challenging and requires careful design and execution, often involving cutting on the high side and filling on the low side.
Matching Canal Types with Alignment
Based on the definitions above, we can match the types of canals with their characteristic alignments:
| Type of Canal | Type of Alignment |
|---|---|
| A. Ridge canal | Aligned along the watershed |
| B. Contour canal | Aligned nearly parallel to the contours |
| C. Side slope canal | Aligned roughly at right angles to the contours |
Let's verify the matching:
- A. Ridge canal is aligned along the watershed (Option 2).
- B. Contour canal is aligned nearly parallel to the contours (Option 3).
- C. Side slope canal is aligned roughly at right angles to the contours (Option 1).
Therefore, the correct matching is A - 2, B - 3, C - 1.
Revision Table: Canal Alignment Characteristics
| Canal Type | Alignment Relative to Contours/Watershed | Irrigation Area | Cross Drainage Needs |
|---|---|---|---|
| Ridge Canal | Along the watershed (highest point) | Both sides | Minimal/None |
| Contour Canal | Nearly parallel to contours | One side (lower side) | Numerous |
| Side Slope Canal | Roughly at right angles to contours | One side (lower side) | Minimal/None |
Additional Information: Factors Affecting Canal Alignment
Several factors influence the choice of canal alignment:
- Topography: The shape and slope of the land are primary determinants. Ridge alignment is best in flat to gently sloping areas, while contour or side slope alignments might be necessary in rolling or hilly terrain.
- Command Area: The area intended to be irrigated dictates where the canal needs to go. A ridge canal can command areas on both sides, while a contour canal is limited to one side.
- Cross Drainage Works: The cost and feasibility of building structures like aqueducts, super passages, and siphons to carry the canal over or under natural streams are major considerations. Alignments that minimize the number of such structures are often preferred.
- Soil Type: The stability of the soil on side slopes can influence the feasibility of a side slope canal.
Understanding these different canal alignment types and their characteristics is crucial in the design and planning of irrigation projects.
Important Questions from Design of Canals
Upon a detailed topographical investigation, an engineer wants to align a canal. Along which of the following should be align the canal?
Which of the following components of the weir divides the river width into weir portion and under sluices pocket?
Which canal irrigates only on one side because the area on the other side is higher?
In which type of canal escapes is the crest of the weir wall kept at R.L. equal to the canal FSL?
If the discharge in canal equals to 70 m3/s with it silt factor √2, the velocity of flow in canal as per Lacey’s theory is
