Uses & Effects of Canal Irrigation

• Cheap labour and availability of cement reduces the cost of canal construction
• Huge quantities of water from Monsoon rainfall & melting of snow can be stored in reservoirs during summer season.
• Irregular supply of water in the rivers is then regulated by construction of dams & barrages. Canal system irrigates a vast area. Even the deserts have been made productive.

Causes:

• Abundance of silt eroded from the Karakoram, Hindu Kush and Himalayan mountains.
• Deforestation - ruthless cutting of trees for fuel and timber. Rivers form narrow and deep valleys in the mountainous areas. Most of the eroded material is washed down into the plains and piles up in reservoirs of the dams.

Effects:

• Blockage of canals because silt accumulates.

• Weakens the foundation of dams.

• Reduced capacity of reservoir and less flow of water affects the generation of hydro-electric power. It also results in availability of less water for irrigation purposes.

• Flow of floodwater is hampered which may cause heavy damage to the dam because of mounds of silt which block the flow of water.

• Large-scale afforestation especially on the foothills of Himalayas.

• Cemented embankment of canals. .

• Installation of silt trap before the water flows to the dams.

• Structural measures such as operating the reservoir at lower level during flood and allowing free flow during low flow season for sluicing sediments from the reservoir.

Uses of Irrigation:

1. Soft soil and level land of the Indus Plain makes digging of canals easier than in the rugged lands of Balochistan.

2. By canal irrigation millions of gallons of water are utilized that would flow into the Arabian Sea.

3. Cheap labor and availability of cement reduces the cost of canal construction

4. Canal system irrigates a vast area. Even the deserts have been made productive.

5. Irregular supply of water in the rivers is then regulated by construction of dams & barrages.

6. Huge quantities of water from Monsoon rainfall & melting of snow can be stored in reservoirs during summer season.

7. Southward slope of the rivers makes construction of canals easier, because water flows southwards naturally.