This page shows statistical data on irrigation of agricultural lands worldwide.
Irrigation is the artificial "abstraction" of water from a source followed by the "distribution" of it at scheme level aiming at "application" at field level to enhance crop production when rainfall is scarce.
Irrigated area.
The appended table gives an overview of irrigated areas in the world in 2003 
Only the countries with more than 10 million ha of irrigated land are mentioned.
(*) Including India, China and Pakistan
There are 4 countries with 5 to 10 million ha irrigated land: Iran (7.7), Mexico (6.3), Turkey (5.1), and Thailand (5.0).
The 16 countries with 2 to 5 million ha irrigated land are: Bangladesh (4.7), Indonesia (4.5), Russia (4.5), Uzbekistan (4.3), Spain (3.8), Brazil (3.5), Iraq (3.5), Egypt (3.4), Romania (3.0), Vietnam (3.0), Italy (2.8), France (2.6), Japan (2.6), Australia (2.6), Ukraine (2.3), and Kazakhstan (2.1)
Area per application method at field level.
94% of the application methods of irrigation water at field level is of the category surface irrigation, whereby the water is spread over the field by gravity.
Of the remaining 6%, the majority is irrigated by methods requiring energy, expensive hydraulic pressure techniques and pipe systems like sprinkler irrigation and drip irrigation, for the major part in the USA. The source of irrigation water in these cases often is groundwater from aquifers. However, the exploitation of aquifers can also be combined with surface irrigation at field level.
In relatively small areas one applies subirrigation whereby the water infiltrates into the soil below the soil surface from pipes or ditches. This category includes tidal irrigation used in the lower part of rivers where the tidal influence is felt by permitting the river water to enter ditches at high tide and allowing it to infiltrate from there into the soil
In relative rare cases one uses labor-intensive methods like irrigation with watering-cans and by filling dug-in porous pots (pitcher irrigation) from where the water enters the soil by capillary suction.
Surface irrigation can be divided into the following types, based on the method by which water is spread over the field after it has been admitted through the inlet:
The first four forms of irrigation come in the category of "flood-irrigation", because the entire surface of the cropped area is wetted, whereas with furrow irrigation, the surface of the ridges remain dry.
The irrigation of sloping fields is called "flow irrigation" as the water on the surface does not come to a stand still and the stream entering the field has to be cut back before the wetting front reaches the end of the field to avoid runoff losses.
Areal growth.
From 1955 to 1975 the annual growth of the irrigated area was almost 3%. From 1970 to 1982 the growth rate was some 2% per year, and from 1983 to 1994 about 1.3% per year. The growth rate of irrigated area is decreasing.
The following table shows the irrigation development in the world between 1955 and 1983, distinguishing developed from developing countries:
The developed countries witnessed a relatively greater increase than the developing nations.
Water use.
Irrigation schemes in the world use about 3 500 km3 water per year, of which 74% is evaporated by the crops. This is some 80% of all water used by mankind (4 400 km3 per year). 
The water used for irrigation is roughly 25% of the annually available water resources (14 000 km3) and 9% of all annual river discharges in the hydrological cycle. 
River discharges occur for the major part in regions with humid climates, far removed from the regions with (semi)arid climates, where irrigation water is most needed. Compared to the 8 600 km3 of annual river discharge in the drier climates only, the yearly water use for irrigation is 40%
Of the total irrigated area worldwide 38% is equipped for irrigation with groundwater, especially in India (39 million ha), China (19 million ha) and the United States of America (17 million ha). Total consumptive groundwater use for irrigation is estimated as 545 km3/year. Groundwater use in irrigation leads in places to exploitation of groundwater at rates above groundwater recharge and depletion of groundwater reservoirs.
Economical significance.
The irrigated area occupies worldwide about 16% of the total agricultural area, but the crop yield is roughly 40% of the total yield. Hence, the productivity of irrigated land is 3.6 times that of unirrigated land. The monetary value of the yield of irrigated crops is some 6.6 times that of unirrigated crops. In irrigated land one grows crops with higher market values.