Understanding Different Irrigation Types

Irrigation is the process of supplying water to crops by artificial means. It is essential for agriculture, especially in areas where rainfall is insufficient or irregular. Different methods of irrigation are used depending on factors like the source of water, the topography of the land, the type of soil, and the crops being grown.

Exploring Irrigation Methods Based on Water Flow

Irrigation methods can broadly be categorized based on how water is supplied to the field. A key factor is whether gravity can be used to move water from the source to the land.

Flow Irrigation

Flow irrigation, also known as gravity irrigation, is a method where water flows from the source (like a canal, river, or reservoir) to the field purely by the force of gravity. This is possible when the water source is at a higher elevation than the land being irrigated. River canal irrigation often uses this method, where canals are constructed to divert water from rivers and let it flow down to the fields.

Lift Irrigation Explained

Lift irrigation is employed when the water source, such as a river, well, or reservoir, is located at a lower elevation than the agricultural land. In such situations, gravity flow is not feasible. Water must be 'lifted' or raised from the source to the required level using mechanical means like pumps. Once lifted to a sufficient height, the water can then be distributed to the fields, sometimes using gravity for the final distribution across the land.

Inundation Irrigation

Inundation irrigation is a type of flow irrigation that relies on the natural flooding of land, typically occurring during periods of high flow in rivers. Water is diverted from rivers into canals during floods and spreads over the land. This method is seasonal and depends heavily on river water levels.

Analyzing the Question Scenario

The question specifically asks about the type of irrigation used when the water supply is at "too low a level to run by gravitation of the land". This means the water source is lower than the land, making gravity flow impossible.

Let's evaluate the options based on this condition:

• Lift irrigation: This method is designed specifically for situations where the water source is lower than the land, requiring water to be mechanically lifted. This perfectly matches the condition described in the question.
• River canal irrigation: While river canals distribute water, the core principle is often gravity flow from the river source. If the river level is too low compared to the land, simple canal diversion won't work unless pumping (lift) is also involved. Without lifting, pure gravity-based river canal irrigation requires a higher source.
• Flow irrigation: This is a broad term for irrigation using gravity flow. If the water source is too low for gravity, flow irrigation in its simple form is not possible.
• Inundation irrigation: This relies on flooding during high river levels and uses gravity to spread water. It is not applicable when the water source is permanently low compared to the land.

Therefore, when the water supply is too low for gravitational flow to the land, lift irrigation is the appropriate method.

Conclusion

The type of irrigation practiced when the water supply is at too low a level to run by gravitation of the land is lift irrigation because it involves mechanically raising water from a lower source to a higher level for distribution.

Revision Table: Key Irrigation Concepts

Additional Information on Lift Irrigation Systems

Lift irrigation systems can vary in scale and complexity. They can range from small, individual farmer-operated pumps drawing water from wells or rivers to large-scale projects involving barrages, reservoirs, and complex networks of pumping stations and canals or pipelines.

Components of a typical lift irrigation system may include:

• A water source (river, well, lake, reservoir).
• An intake structure to draw water.
• Pumps (electric, diesel, or solar-powered) to lift the water.
• Pipelines or channels to transport the lifted water to the command area.
• Distribution networks (canals, pipes, or field channels) to deliver water to individual fields.

Lift irrigation is crucial in regions with undulating terrain or where groundwater is the primary source, as groundwater is typically below the surface level of the land.