Irrigation

I. Global Irrigation Overview
– In 2000, the total fertile land equipped for irrigation was 2,788,000 km² worldwide, with Asia holding 68% of irrigated land.
– By 2012, irrigated land increased to an estimated 3,242,917 km², with 20% of farming land contributing to 40% of food production.
– In 1990, 30% of global food production came from irrigated land.
– Irrigation techniques include canals, groundwater pumping, and water diversion from dams.
– Global land area equipped for irrigation reached 352 million ha by 2021, with Asia having 70% of the total.

II. Water Sources for Irrigation
– Irrigation water can be sourced from groundwater, surface water, treated wastewater, or non-conventional sources.
– Floodwater harvesting is an accepted irrigation method, while rainwater harvesting is not typically considered irrigation.
– Benefits of using recycled water for irrigation include lower costs and consistent supply regardless of water restrictions.

III. Environmental Impact of Irrigation
– Environmental effects of irrigation include changes in soil and water quantity and quality.
– Problems from irrigation include depletion of aquifers, over-irrigation, and soil salinity.
– Deep drainage from over-irrigation can cause rising water tables, requiring watertable control through drainage.

IV. Irrigation Methods
– Various irrigation methods are available, aiming for uniform water supply to plants.
– Methods include surface irrigation, drip irrigation, sprinkler irrigation, and center pivot irrigation.
– Surface irrigation is the oldest form, with different types suitable for various terrains.

V. Advanced Irrigation Techniques
– Drip irrigation delivers water near the root zone, offering high water efficiency.
– Sprinkler irrigation uses high-pressure sprinklers or guns for water distribution.
– Center pivot irrigation utilizes wheeled towers to irrigate all types of terrain.
– Subsurface irrigation delivers water directly to the root zone, reducing evaporation and runoff.