Canal irrigation: types, advantages, disadvantages and design

Agriculture is the engine that drives national progress, and water is the single most important component that farmlands need to be cultivated. The productivity of irrigated land is at least double that of rainfed land, allowing for increased output intensification and crop variety. To achieve efficient outcomes in agriculture, canal irrigation plays an important role. The practice of irrigation by canals has the goals of lowering the rate of erosion, stopping the deterioration of the water’s quality, increasing the amount of water that is used effectively and, most importantly, decreasing the amount of water that is lost through seepage or structural failure.

Table of Contents

What is canal irrigation?

A canal is an artificial waterway that is built to bring water to the fields so that irrigation can be performed. The water comes either from a tank or reservoir, or it comes directly from the river.

The canals can be built out of concrete, stone, brick, or any kind of flexible membrane that resolves difficulties of durability like seepage and erosion. Alternatively, the canals can also be dug out of the ground.

How does canal irrigation work?

To ensure that the agricultural fields get an adequate amount of water flow, the canals have been constructed with the appropriate breadth and depth. From the place where the water is drawn, it will be dispersed throughout the various agricultural areas in the appropriate way.

Controlling the flow of water from its source to the agricultural fields using appropriate valves is possible. As soon as the water reaches its intended location, it will be pushed into the agricultural field, either manually or automatically, depending on the circumstances. The slope of the agricultural field will have a very minor contour added to it to facilitate the natural flow of water.

Canal irrigation system: Distribution network

The water that is being carried from the place of origin will divide into many channels so that it may be delivered to all of the necessary locations. The following is an explanation of the many components that make up the canal irrigation system.

The Main Canal

Main canals are defined as those with a discharge of 10 cumecs or more. The primary canal, or arterial canal, is the body’s primary blood vessel. The main canal is the drainage system’s highest-ranking canal, and it is responsible for carrying water from the other drainage canals to the water intake. The main canal is inaccessible for direct irrigation.

Branch Canal

The typical range of discharge for branch canals is 5-10 cumecs. Each of the main canal’s branches can go in either direction at regular intervals. The maximum head discharge into this canal is around 14–15 cumecs from the main canal. In addition to its primary function, a branch canal also acts as a feeder channel for larger and smaller tributaries.

Major distributary

Major distributaries are canals that receive water from the main canal or a branch canal with a head discharge of 0.028% to 15.0 cumecs. Their output is lower than that of branch canals since they sometimes draw their water supply from the main canal. Because water is piped through these channels and onto the field, they are often referred to as irrigation channels.

Minor Distributary

Minor distributaries are canals where the discharge was between 0.25 and 3 cumecs. Discharges of 0.25 cumecs or less from a large distributor are considered to be modest. Sometimes the branch canals will feed a small distributary. Minor distributaries have a smaller discharge than large distributaries. Furthermore, they provide water to the courses through the faucets that are installed beside them.

Watercourse or Field Channel

In the watercourse channel, the stream discharge is less than 0.25 cumecs. A field channel can originate from a big distributary or a small one, depending on the scope of the irrigation. In a few instances, the field is additionally supplied with water from the branch canal.

The canal distribution system is comparable to how energy is transmitted from the powerhouse to your home. The quantity of water that must be transported to the agricultural regions will decide the canals’ width as well as their depth.

The stream from the river will provide the main canal with a considerable volume of water. Therefore, both the width and the depth of the channel will be significant. After that, the flow will be distributed to the branch line according to the sub-branch and the distributor line, as well as to the minor lines, via the central canal. At last, we arrive at the agricultural fields.

Why should canals not have curves or bends?

Source: Pinterest

It is important at all times to straighten up the canals so that there are no bends. The flow is disrupted as a consequence of the curves. This causes the inner curvature of the canals to get silted in as it scourges the outside edge of the canals. It is essential that pitching be given to prevent scouring on the concave side. For the canal bends to be able to accommodate massive discharges, they need to be softer and possess a larger radius.

Types of canal irrigation systems

In canal irrigation systems, there are primarily two types of canals used.

Inundation Canals

They are extracted from rivers and do not have any kind of weir or other structure at the head of the river to control the flow of water coming out of the river. Canals similar to this may be found in the Brahmaputra valley and the plains of the Sutlej and Ganga rivers.

Perennial Canals

These canals maintain a steady flow of water throughout the year, especially during the colder winter months, and they get their water supply either from rivers or from reservoirs that are part of river project reservoirs. A weir is constructed underneath the intake of the canal, and the intake itself has sluice gates to control the flow of water.

See also: All about waterways

Designing a canal irrigation system: Things to consider

The following factors will be taken into consideration while planning the path of the canal:

The path of the canal should go through all of the farmlands so that it can supply water.
The course of the canal, which is straight, will assist to maintain the appropriate velocity of the water flow, and it will also help to limit the amount of heat loss that occurs.
The shorter length of the canal, which covers all of the areas that are used for agriculture, will lower the expenses of construction and the work that is required for cross drainage.
The canal path that is shorter and more direct will lower the amount of water that is lost as a result of seepage and evaporation.
Because it causes unneeded complications and delays in the building work, the path of the canal shouldn’t be designed to pass through any forest area, villages, towns, or other settlements of any kind.
It is recommended that you do not take the canal path that goes through the rock region.
Adding more bends to the canal is something that has to be avoided as it slows down the flow of water.
It is important to strike a balance between digging into the soil and filling it in if you want to keep building costs down.
Since gravity force is responsible for the movement of the water, the canal line should be planned appropriately.
When there is a scarcity of rain throughout the growing season, farmers will benefit from having an effective irrigation system.
It helps to speed up the effort involved in the cultivation, and it also helps to speed up the economy.
It contributes to a rise in the level of groundwater.
Canals facilitate not only the production of power but also the delivery of potable water.

Advantages of canal irrigation

The following is a list of the primary benefits of canal irrigation:

If you have an effective irrigation system, you will be able to satisfy the needs of your crops even when there is a variation in the amount of rainfall.
Canals provide for greater output per hectare of land as compared to other methods of watering, such as traditional irrigation.
The canals that were created are permanent and need to be maintained regularly.
Severe floods can be prevented, hence accelerating economic growth.
Helps in the development of arid wasteland.
Irrigation using canals prevents the groundwater table from falling to a lower level. It does nothing more than assist in raising the water level, which in turn makes the drilling of wells easier.
In addition to their use in transportation, canals contribute to the development of fisheries, provide sources of potable water, and generate hydroelectricity.

Disadvantages of canal irrigation

Because of the constant presence of water in the canal, the population of insects, mosquitoes, and worms increases, paving the way for water-borne diseases.
Any inequity in the manner in which water is distributed leads to the shortage of water in certain regions and the accumulation of sediment in water supplies in other regions. Because of this, the soil is rendered unproductive as a result of the flow of potentially damaging salts and alkalis from deeper levels to the surface.
The capacity of the canal is reduced as a consequence of improper maintenance, which causes sediments to gather in the canals and reduces their overall capacity.
The building of a canal requires both financial commitment and a significant amount of time. As a result, this is not a solution for irrigation in all cases.

Canal irrigation in India

Canal irrigation is one of the most important sources of irrigation for farmlands across India. It accounts for nearly 24% of the total irrigated land in the country. This effective source of irrigation has greatly benefited deep fertile soil, low-level relief, and perennial river areas. Canal irrigation is more prevalent in the northern plains as compared to other parts of the country. One of the reasons behind the decline of the prevalence of canal irrigation in India is the heavy maintenance required to ensure efficiency.

FAQs

Why do we rely on canal irrigation?

The water table level is kept stable by canal irrigation. In addition to facilitating transportation and the generation of hydropower, water for human use, the expansion of fisheries, and more can be accessed through canals.

Which method of irrigation is superior?

Clean groundwater or water from an irrigation canal is ideal, provided it does not contain mud.

Why is canal irrigation the most prevalent method in India?

Canal irrigation is prevalent in the northern plains because the land in this region is porous, and groundwater levels are high. In the northern plain of India, canals are constructed near rivers to facilitate the movement of water everywhere. They are also sensible and government-conserved.

Which state has the most irrigation canals?

Uttar Pradesh has the majority of the country's canal-irrigated land area. Other important states using canals for irrigation include Punjab, Haryana, Madhya Pradesh, Bihar and Andhra Pradesh.

Was this article useful?

😃 (1)
😐 (1)
😔 (0)

Housing News Desk

Housing News Desk is the news desk of leading online real estate portal, Housing.com. Housing News Desk focuses on a variety of topics such as real estate laws, taxes, current news, property trends, home loans, rentals, décor, green homes, home improvement, etc. The main objective of the news desk, is to cover the real estate sector from the perspective of providing information that is useful to the end-user.

Facebook: https://www.facebook.com/housing.com/

Twitter: https://twitter.com/Housing

Email: [email protected]