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Irrigation covers about 200 million hectares of agricultural land in the world. Asia has the largest irrigated acreage in the world. Percentage of irrigated land is considerably small in other continents. For example, the percentage amounts to 8 in North America, 7 in South America and 5 each in Oceania and Africa. In the Russia only 5 percent of the cultivated land is under irrigation.

Egypt stands out in respect of irrigation. Egypt is practically a desert receiving only 15 cm to 20 cm of rainfall. In fact 100 per cent of agriculture is carried out under irrigation, drawing water from the Nile. This type of irrigation is called Basin Irrigation. The construction of Aswan dam has brought about further strength in the irrigation system of Egypt. This dam across the Nile helps the year round irrigation of 16.4 million square meters of agricultural land. In South Africa Orange Basin Project also irrigates vast areas of agricultural land. In North America, U.S.A. has the largest area under irrigation. This country ranks third in the world in respect of irrigated acreage. Only 9 per cent of the agricultural land is irrigated. In the United States of America there is dearth of water in the Western desert and southern California. In Mexico about 16 per cent of the agricultural land is irrigated. The South Demingo region of the Mexicali valley is most developed in respect of irrigation. Of the three countries of North America Canada is least developed having only 1 per cent of agricultural land been brought under irrigation.

Russia has 10 million hectares of cultivated land under irrigation. Of this total, 87 and 11 percent are accounted for by the dry and the Steppe regions respectively. Irrigation had brought a revolutionary change in the Soviet agriculture days.

In Europe, excluding Russia , 65 percent of the irrigated acreage falls within the Mediterranean region, especially in Italy, Spain and southern France. In Italy the Alpine rivers and lakes are the main sources of irrigation water. The Po, different fountains and the Artesian wells also remain important bases of irrigation. In Spain there are as many as 140 reservoirs, which collect nearly one third of the river, flow in order to subsequently irrigate the thirsty land.

Peru is the most developed country in South America in respect of irrigation, although Brazil and Argentina far outrank it in terms of irrigated acreage. Australia is the lone country in Oceania where irrigation is notably developed. About I million hectares of land are irrigated in Murray-Darling basin. The sugarcane plantation in Queensland largely depends on underground water.

China, India and Pakistan account for four-fifths of the irrigated acreage in Asia. In fact, China leads the world with its 76 million hectares of irrigated acreage. Nearly 70 percent of the agricultural land is irrigated. The Tukiang dam and the 1,1000 km long Imperial canal built in 200 B.C. and 700 A.D. stand witness to a glorious tradition in irrigation.

With regard to irrigation, Pakistan is quite outstanding in the world because of its-well-knit and immaculate irrigation system. The irrigation network in Pakistan fans out from Islamabad in the northern part of the Indus Valley down to the mouth of the Indus in the South. The Sukkur Barrage, Tarbela Dam and the Mangla Dam are some of the landmarks of the irrigation landscape of Pakistan. Tarbela is the largest dam in the World made up of clay and stone. The Mangla dam has connected Jhelum with the Indus.

Iran, Iraq, Indonesia and Japan are notably developed in irrigation. In Iran about 5 million hectares of land are irrigated with the help of very old tunnel system, called Quanatas or Karrez. The ancient civilization of Iraq on the Tigris and Euphrates owed largely to the excellent irrigation system. At present there are about 4 million hectares of irrigated land, and this is mainly attributed to the Hindiya and Musaeb dams and Al Kut barrage on the Tigris.

About 60 percent of the agricultural land is irrigated in Japan. Irrigation in Japan is primarily based on canals and tanks. A traditional method of irrigation in Indonesia is to divert the stream waters by blocking the courses with the help of boulders. This is how about 4 million hectares of land are irrigated in that country.

India ranks second in the world to China in respect of total irrigated acreage. But the proportion of irrigated land to the cultivated land amounts to only 30 percent against 70 percent in China. Out of the total of 44 million hectares of irrigated land, 26 million hectares are m Ganga-Brahmaputra valley, 12 million hectares in the Godavari-Krishna-Cauvery delta region, 4 million hectares in Central India and the remaining 2 million hectares are in the arid and semi-arid parts of Western India.

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