Types of irrigation are mainly divided into two- Lift irrigation and flow irrigation. Flow irrigation is further divided into perennial and inundation irrigation. Inundation irrigation is again subdivided into three. They are direct irrigation, storage irrigation and combined System. We are going to meet the huge family in the blog.
Irrigation is mainly two types.
- Flow irrigation
- Lift irrigation
The figure below is a schematic diagram showing the types of irrigation.
Let’s get into each of them in detail.
Flow irrigation- Major among types of irrigation
Flow irrigation is that type of irrigation in which the supply of irrigation water available is at such a level that it is conveyed on to the land by the gravity flow. Flow irrigation is divided into three types.
- Perennial irrigation system
- Inundation or flood irrigation system
So, what are these? Relax. We will take one at a time and learn.
Perennial irrigation system
In perennial irrigation system, the water required for irrigation is supplied in accordance with the crop requirements throughout the crop storage. Weirs or barrages are required to store the excess water during floods and release it to the crops as and when it is required.
Inundation irrigation is carried out by deep flooding and thorough saturation of the land to be cultivated which is then drained off prior to the planting of the crop.
Depending upon the source from which the water is drawn, inundation irrigation can be further subdivided into 3 types.
- Direct irrigation or river canal irrigation
- Storage irrigation
- Combined System
Now, what? Let’s peep into each of them to make friends with them.
Direct irrigation or river canal irrigation
We are going to jump right into the details of direct irrigation now.
- In this direct irrigation system, water is directly diverted to the canal without attempting to store the water. For such a system, a low diversion weir or diversion barrage is constructed across the river.
- This raises the water level in the river and thus diverts the water to the canal taking off upstream of the weir, as shown in figure.
- Generally, a direct irrigation scheme is of a smaller magnitude, since there are no rigid controls over the supplies. One or two main canals may take off directly from the river.
- Cross- drainage works are constructed wherever natural drains or distributary streams cross the canals. In a bigger scheme, there may be branch canal taking off from the main canal
Learnt about direct irrigation, right? Let’s move on to storage irrigation next.
What are we waiting for? See the basic knowledge about storage irrigation now.
- In storage irrigation system, a solid barrier, such as a dam or a storage Weir is constructed across the river and water is stored in the reservoir or lake so formed.
- Depending upon the water requirements of crops, or the hydroelectric power generation, and upon the flow of water in the basin at the site construction, the elevation storage curve for the reservoir is known.
- The height of the dam is then decided from this curve, corresponding to the storage- volume required.
- Storage irrigation scheme is comparatively of a bigger magnitude, and involves much more expenditure than a direct irrigation scheme.
- One or two main canals take off from the reservoir. Due to the formation reservoir, some land property may be submerged to the upstream of the dam.
- A network of canal system convey water to the agricultural fields, through various regulatory works.
- Cross-drainage works such as aqueducts, syphon aqueducts, super passages and canal syphons are constructed wherever natural drains cross the canals
Time to meet the last member in flow irrigation system. Who’s that? Of course, combined system.
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We have seen that in the storage irrigation system, water is stored in the reservoir, since the river is not perennial, while in the direct irrigation system, the river is perennial and hence the water is diverted from the river to the canal.
Sometimes, a combined scheme is adopted in which the water is first stored in the reservoir formed at the upstream side of the dam, and this water is used for water power generation.
The discharge from the power house is fed back into the river, to the downstream side of the dam. Thus, sufficient quantity of flow is again available in the river.
At a suitable location in the downstream, a pick up weir is constructed. This weir diverts the water from the river to the canal.
How can we leave the second main among the types of irrigation alone? Shake your hands with lift irrigation now.
Lift irrigation- second among types of irrigation
Lift irrigation is practiced when the water- supply is at too low a level to run by gravitation on to the land.
In such a circumstances water is lifted by mechanical means. Irrigation from wells is an example of lift irrigation, in which sub- soil water is lifted up to the surface and is then conveyed to the agricultural fields.
Now that you know all types of irrigation, how do you choose the right one for your requirement?
Choice between types of irrigation
Direct irrigation scheme is adopted in the circumstances where the river is perennial and has a normal flow throughout the irrigation season, never less at any time than the requirements of the field.
On the contrary, storage irrigation system is adopted when the river flow is either not perennial, or where flow is insufficient during certain parts of the crop season for irrigation requirements.
In a multistage river valley development, a combined storage- cum diversion scheme is more useful.
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