has been known for as long as people have been cultivating plants. Irrigation is the controlled process of using water for crops where rainfall is not enough. This process is vital for the human race, because through it and agriculture the population of the earth is supplied with enough food. Except for drinking water, water for agriculture is the most important use of water – about 60 per cent of the entire world’s fresh water reserves are used for irrigation. Without it, growing crops will be impossible for many nations and there will be shortage of the food supply.
Many different irrigation methods are used around the world, depending on the financial resources, water supply and the type of crops.
Surface irrigation is an ancient irrigation method that is still used today, mainly in the less-developed countries, due to its simplicity and low cost. There are two types of surface irrigation – flood and furrow irrigation. Flood irrigation is used in areas where there is a rich source of water. For this method a large amount of water is poured to the field among the crops. It can be applied only to flat lands, so the water is not wasted and the water supply is equal to all parts of the field. This irrigation method was used in Ancient Egypt where the Nile will flood the fields with crops. The advantages of this method are that it is simple and cheap, but not very efficient.
Furrow irrigation is similar to flood irrigation, but it is a little bit more advanced. The water is inserted into small channels between the rows of the field, instead of the whole field. This method is cheap and suitable for areas with abundant water sources and is more efficient than simple flood irrigation.
Another type of irrigation is the spray irrigation. In spray irrigation water is sprayed on both sides of the field through special system. It is more expensive and more technological irrigation method, as it requires machinery, but it is more efficient and less water is required.
There are two types of spray systems – the center-pivot system and the low energy precision application center pivot system. The traditional center-pivot system is a spray irrigation that is used for watering large territories with minimum machinery. It is a mechanized method that uses moving spray guns or dripping faucet heads that pivot around a central source of water. The fields using these systems for irrigation can be easily recognized from air, because they have the shape of a circle. The disadvantages of this method are that a lot of electricity is needed for the motors of the system, as well as large amounts of water, as most of it is lost in the air. It is suitable for developed areas with rich water sources.
The Low Energy Precision Application (LEPA) center pivot system is an irrigation method more efficient that the traditional center pivot system. With this method, the water is released directly on the crops, instead of being sprayed into the air. In that way less water and electricity are used. It is used in arid and semi-arid areas to maximize the use of water supply and significantly increase efficiency.
Drip irrigation is the most expensive method of irrigation, because it is the most technologically advanced one and at the same time the most efficient one in terms of water use. This system consists of perforated pipes that are positioned by rows of crops and water directly the crops without wasting water. This irrigation method is usually used to water fruits and vegetables. Its advantages are that it is more efficient than the other methods, but more expensive and advanced.
When drip irrigation laterals are buried at a depth of 50cms it is called buried irrigation. For this irrigation system a special material that protects the drippers is introduced – Tarplan. It prevents sprouting near the dripper. Different types of drippers have been developed – line drippers, regulated and unregulated fixed drippers, and integrated drippers onto the wall of the irrigation lines. The buried irrigation system is used in extremely dry regions that have limited water resources. Israel uses that kind of irrigation system and has developed series of other irrigation methods that make the best use of their water sources.
When water is used for domestic purposes or industrial ones, about 90 percent of the water returns to the environment and to the water sources. When water is used for irrigation only one half of the water used returns to the environment, most of it is lost due to evaporation or evapotranspiration. That fact defines the importance of irrigation system and finding the most efficient one to save water resources.
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Kibaroglu, A. (n.d.). Design and Management of Irrigation Systems: The Southeastern Anatolia Development Project. Retrieved May 6, 2011, from The International Development Research Centre: http://www.idrc.ca/cp/ev-42840-201-1-DO_TOPIC.html
Susan S. Hutson, N. L. (2004). Estimated Use of Water in the United States in 2000. USGS Circular 1268.