The canal is a long, thin stretch of water that is artificially constructed to convey water from rivers, reservoirs or either for boats to travel along or for taking water from one area to another.
Classification of Canals based on Various Factors
Canals are classified into different types which are as follows :
- Based on the nature of the supply source
- Based on functions
- Based on the type of boundary surface soil
- Based on the financial output
- Based on discharge
- Based on canal alignment
Based on the Nature of Supply Source
- Permanent Canal
- Inundation Canal
1. Permanent Canal:
It is a type of canal in which water is accessible throughout the year. This type of canal is generally run from a permanent source of supply water. Several Permanent hydraulic structures are built in this type of canal for water distribution and regulation. A Permanent canal is also known as a perennial canal.
2. Inundation Canal:
It is a type of canal in which water is accessible only during the flood. These types of canals are carried off from rivers to control the high water level in rivers during flood periods. A head regulator is provided to regulate the flow into the canal.
Based on Functions of Canal
- Irrigation canal
- Power canal
- Feeder canal
- Carrier canal
- Navigation canal
1. Irrigation canal:
A canal arranges in a straight line along the boundaries of cultivatable areas to supply water for agriculture purposes is said to be an irrigation canal.
2. Power canal:
A canal build which is mostly used for the generation of hydraulic power is titled a power canal.
3. Feeder canal:
A feeder canal is build to supply two or more other canals or branch canals.
4. Carrier canal:
A carrier canal is a multi-purpose canal which provides both irrigation canal and feeder canal. It defines the carrier canal feeds the other canals as well as provides water for direct irrigation.
5. Navigation canal:
A canal that is built mostly for navigational purposes is known as navigation canal. The water level needed in a navigation canal is usually a lot higher to sufficient space for large ships, vessels, etc.
Based on Type of Boundary Surface of Canal:
- Alluvial canal
- Non-alluvial canal
- Rigid Surface canal
1. Alluvial canal:
If the canal is constructed by digging in alluvial soils such as silt, sand, gravel, etc. then it is called an alluvial canal.
2. Non-alluvial canal:
If the surface of the canal is non-alluvial soils such as loam, clay, rock, etc. then it is called a non-alluvial canal.
3. Rigid Surface canal:
Rigid surface canals come under non-alluvial canals but the boundary surface of the canal is lined with a hard layer of lining material such as cement, concrete, stones, etc.
Based on Financial Output
- Protective canal
- Productive canal
1. Protective Canal:
Protective canals which are constructed to save a particular area from the shortage of water. The main aim of a protective canal is to fulfill the needs of cultivators during the time of famine.
2. Productive Canal
Productive canals are those which will produce more revenue for its maintenance and running costs and also to recover the initial investment done on the construction of the canal. It is good if it recovers 6% of its initial investment per annum.
Based on Discharge
- Main canal
- Branch canal
- Major distributary canal
- Minor distributary canal
- Field canal
1. Main canal:
The main canal leaves the ground, directly from a river or reservoir. It carries water in large amounts to feed the branches of canal and distributary canals. Due to the conveying of more discharge through the main canal, it is not suggested todo direct irrigation from it.
2. Branch Canal:
The branch canal which leaves the ground, from main canals at regular intervals. These canals supply water to major and minor distributary canals. The discharge of the branch canal is usually over 5 m3/sec. In this case of branch canals also, direct irrigation is not suggested until their water carrying capacity is less.
3. Major Distributary Canal:
Major distributary canal leaves the ground, from the branch canal or in few cases from the main canal. They supply water to the minor distributaries and field channels. A canal is called to be a major distributary when its discharge lies between 0.25 to 5 m3/sec.
4. Minor Distributary Canal:
Minor distributary canal leaves the ground from major distributaries and directly from branch canals depending upon the discharge of canals. Their discharge is usually below 0.25 m3/sec. These canals provide water to the field channels.
5. Field Channels:
Field channels are also called as watercourses are excavated by cultivators in the irrigation field. These channels are feed by the distributary canals and branch canals through canal outlets.
Based on Canal Alignment
- Ridge canal
- Contour canal
- Side-slope canal
1. Ridge Canal:
A canal arranges in a straight line along the ridgeline or watershed line of an area to be ridge canal or watershed canal. Since it is running at the high altitude of the area, irrigation on both sides of the canal up to a larger extent area is possible. There is no interception of natural drains on ridgelines hence, no cross drainage works are needed for this type of canal.
2. Contour Canal:
A canal arranges in a straight line roughly parallel to the contours of the area is known as the contour canal. This type of canal can be observed in hilly regions. Since it is parallel to the contour line, the ground on one side of the canal is higher and hence irrigation is possible only on the other side of the canal. A contour canal has to flow the drainage and hence cross drainage works are needed to be provided.
3. Side-slope Canal:
A canal arranges in a straight nearly perpendicular to the contour of the area is called a side-slope canal. It is situated neither on the ridgeline nor on the valley line but is exactly in between them. It is parallel to the natural drainage line and hence no cross drainage works are needed. The bed slope of the side canal is very rising.