Irrigation, disadvantages, scope in Nepal

Irrigation

Irrigation is the artificial application of water to land to supply the moisture that crops need for growth when natural rainfall is insufficient.

Disadvantages of irrigation

• Waterlogging and a rising water table from over-irrigation and seepage.
• Salinity and alkalinity of the soil from salts left behind after evaporation.
• Mosquito breeding, so malaria and other water-related diseases may increase.
• High cost of construction and maintenance; possible displacement of people.
• A damp climate and cooler weather around large canals.
• Possible conflicts over water and loss of natural flow downstream.

Scope in Nepal

• Cultivable land is about 2.6 million ha, and a large part of it (especially in the Terai) can be irrigated, but only about half has irrigation, so there is wide scope for expansion.
• Rainfall is concentrated in the monsoon, so winter and spring irrigation is needed.
• Large perennial rivers (Koshi, Gandaki, Karnali, Mahakali) give abundant water for canals, and groundwater in the Terai is plentiful.
• The hills have scope for small, lift, drip and sprinkler irrigation.
• Irrigation raises food production and farmers' income and supports multipurpose development.