Canal irrigation or aqueducts are open streams whose primary role is to carry water from one place to another.
They are the principal canals that give water to one or more fields.
A canal is a man-made trench that is built to transport amounts of water for agriculture.
In this article you’ll learn:
What is Canal Irrigation?
Purpose of Canal Irrigation.
Types of Canal Irrigation.
Merits and Demerits of Canal Irrigation.
So, if you’re ready to go with Canal Irrigation, this article is for you.
Let’s dive right in.
What is Canal Irrigation?
It is a method of irrigation in which water from the reservoir is conveyed to the field through ducts of a specific size and bed channel slope.
Depending on the type of soil, the form is often trapezoidal or triangular, with a slope of the soil.
The water is drawn from a river, a tank, or a reservoir.
Purpose of canal irrigation:
The canal plays a major role in transit and world trade.
Canals are commonly used for irrigation and drainage for urban water supply, hydropower generating, freight transportation, and electricity production.
Canals can be built with concrete, stone, brick, or any type of curved structure that overcomes durability concerns like leakage and erosion.
A canal is an artificial conduit built to transport water from rivers, reservoirs, and other bodies of water for a variety of uses such as power production, navigation, irrigation, and so on.
Canals are categorized into distinct varieties depending on variables such as the characteristics of the main supply, purposes, border surface, economic output, discharge capacity, and canal alignment.
Types of Irrigation Canal:
Depending on the nature of the supply source:
1. Permanent Canal:
A permanent canal is a type of canal that has water accessible all year.
This type of canal is often diverted through a permanent supply reservoir.
In this form of the canal, many permanent hydraulic structures are constructed for water management and distribution.
The perennial canal is another name for the permanent canal.
2. Inundation Canal:
An inundation canal is a form of the canal where water is only accessible during floods.
These canals are cut into rivers to manage the water level during floods.
To manage the flow into the canal, a canal heading controller is provided.
Depending on Canal Functions:
1. Canal for irrigation:
An irrigation canal is a canal that is oriented along the limits of cultivatable regions to deliver water for agricultural purposes.
2. Power canal:
A power canal is a canal built specifically for the generating of hydraulic power.
3. The Feeder canal:
A feeder canal is designed to feed two or even more extra canals or subsidiary canals.
4. Transporter canal:
A carrier canal is a multi-purpose canal that serves as an irrigation canal as well as a feeder canal.
This means that the transport canal both feeds the other canals and supplies water for direct irrigation.
5. Canal of navigation:
A navigation canal is one that is built specifically for navigational operations.
A navigation canal’s water level is often much higher to allow huge ships, vessels, and so on.
Based on type of boundary surface of canal:
1. Canal alluvial:
An alluvial canal is one that was excavated on alluvial soils such as sediment, gravel, pebbles, and so on.
2.Alluvial non-alluvial canal:
Non-alluvial canals have a border surface composed of non-alluvial soils such as soft clay, mud, sandstone, and so on.
3. Strong Surface Canal:
Non-alluvial canals include constrictive surface canals, but the canal’s boundary surface is lined unnecessarily with a hard layer of lining material such as concrete, shotcrete, gravel, and so on.
Based on Financial Output:
1. The Protective canal:
Protective canals are comfort works that are built to safeguard a certain area from a lack of water.
The primary goal of a protected canal is to meet the needs of growers during times of starvation.
2. The Productive Canal:
Productive canals are ones that generate enough cash to pay their operating and maintenance costs as well as the original investment placed in the canal’s development.
It is deemed good if it earns 6% of its initial investment each year.
Based on Discharge:
1. Main canal:
The mainline canal emerges from a watercourse or reservoir.
It transports a huge volume of water to replenish the subsidiary and distributary canals.
It is not suggested to undertake direct irrigation from the canal system due to the conveyance of very high flow.
2. Canal Branch:
At periodic intervals, branch canals split out from major canals.
These canals provide water to both main and smaller distributary canals.
The outflow of the branch canal is often greater than 5 m3/sec.
Direct irrigation is not suggested for branch canals until their water carrying capacity is very limited.
3. The Main Distributary Canal:
The major distributary canal branches of the branch canal or, in certain situations, the main canal. They provide water to smaller distributaries as well as field canals.
When the outflow of a canal ranges between 0.25 and 5 m3/sec, it was shown to be a major distributary.
4. Minor Distribution Canal:
Depending on the discharge of canals, minor distributary canals branch out from main distributaries and occasionally straight from branch canals.
Their discharge rate is typically less than 0.25 m3 /sec. These streams provide water to the field canals.
5. Field Channels:
Field channels also referred to as watercourses, are tiny channels constructed in the irrigated field by cultivators.
The distributary and branch canals feed these waterways via canal exits.
Based on Canal Alignment:
1. The Ridge Canal:
A canal that runs along a region’s ridgeline or drainage line is referred to as a ridge canal or watershed canal.
As it runs at the area’s highest point, irrigation on both sides of the canal is feasible to a greater extent.
Because natural drains are not interrupted on ridges and valleys, this type of canal requires no cross-drainage works.
2. Contour Canal:
A contour canal is a canal that runs substantially along the area’s contours.
This style of the canal is common in hilly areas. Because it runs along the contour line, the terrain on one side of a river is higher, allowing irrigation only on the opposite side.
Cross drainage operations are required because a contour canal must run throughout the drainage.
3. Canal on a Slope:
A side-slope canal runs nearly crosswise to the terrain’s contour.
It is not on the ridgeline or the valley line, but rather somewhere in the middle.
There are no crossing drainage works required because it goes along the natural drainage system.
Alignment of the Canals:
The canal orientation is determined by the following factors:
Canal alignment must be set such that the most area is provided with the least amount of length. It must also reduce the utilization of cross-drainage activities.
There is reduced head loss, seepage loss, and evaporation loss when the canal length is small. This provides more irrigation areas.
Maintaining a straight alignment helps to decrease loss.
Always choose a canal alignment with the least amount of cross-drainage work.
The canal must not travel through forestry, city, village, or expensive location, which reduces the possibility of receiving large damages.
Ridge canals are one type of canal that helps to irrigate both sides of the canal.
It must assist to eliminate heavy cutting and filling, avoiding costly embankment building.
It’s critical to achieve a ratio between cutting and filling depths.
Alignment across brackish, stony, or fractured strata must be prevented.
Advantages of Canal Irrigation:
Non-irrigated barren growth.
Fatal droughts can be avoided, thus accelerating economic growth.
An efficient irrigation system can meet the water requirement of the crop in fluctuations in rainfall intensity.
Canals yield more per hectare of land than conventional irrigation methods.
The canals built are permanent and need regular maintenance.
Irrigation of the canal prevents ground water from flowing down. It only works to raise the water level and, facilitate well excavation.
The canals also provide hydropower, drinking water, fisheries development, and water transportation.
Disadvantages of Canal Irrigation:
Any imbalance in the water distribution system causes water scarcity in some regions and obstruction in others.
Due to the transfer of toxic salts and salts to the surface level, the soil becomes infertile.
The presence of stagnant water in the canal promotes the growth of worms, insects and pests.
Poor maintenance causes siltation in the canal, reducing its capacity of the canal.
Canal development requires both financial and time investment. As a result, it is not a universal option for irrigation.
Also read: Canal Lining | Weir | Culverts | Cross Drainage Work
Canal Irrigation is widely acknowledged to be a major driver in promoting development in many nations.
However, if followed irresponsibly, it may become the generator of agricultural catastrophe, manifested in the form of irrigated agriculture salinity.