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Irrigation: the story on HearLore | HearLore
Irrigation
Archaeological investigation has found evidence of irrigation in areas lacking sufficient natural rainfall to support crops for rainfed agriculture. Some of the earliest known use of the technology dates to the 6th millennium BCE in Khuzistan in the south-west of Iran. The site of Choga Mami, in present-day Iraq on the border with Iran, is believed to be the earliest to show the first canal irrigation in operation at about 6000 BCE. Irrigation was used as a means of manipulating water in the alluvial plains of the Indus Valley Civilization, the application of which is estimated to have begun around 4500 BCE and drastically increased the size and prosperity of their agricultural settlements. Farmers in the Mesopotamian plain used irrigation from at least the third-millennium BCE. They developed perennial irrigation, regularly watering crops throughout the growing season by coaxing water through a matrix of small channels formed in the field. Ancient Egyptians practiced basin irrigation using the flooding of the Nile to inundate land plots which had been surrounded by dikes. There is evidence of the ancient Egyptian pharaoh Amenemhet III in the twelfth dynasty (about 1800 BCE) using the natural lake of the Faiyum Oasis as a reservoir to store surpluses of water for use during dry seasons. In sub-Saharan Africa, irrigation reached the Niger River region cultures and civilizations by the first or second millennium BCE and was based on wet-season flooding and water harvesting. Evidence of terrace irrigation occurs in pre-Columbian America, early Syria, India, and China. In the Zana Valley of the Andes Mountains in Peru, archaeologists have found remains of three irrigation canals radiocarbon-dated from the 4th millennium BCE, the 3rd millennium BCE and the 9th century CE. These canals provide the earliest record of irrigation in the New World.
Modern Methods And Mechanics
Surface irrigation, also known as gravity irrigation, is the oldest form of irrigation and has been in use for thousands of years. In surface systems, water moves across the surface of agricultural lands to wet it and infiltrate into the soil. Water moves by following gravity or the slope of the land. Surface irrigation involves a significantly lower capital cost and energy requirement than pressurized irrigation systems. Hence, it is often the irrigation choice for developing nations, for low-value crops and for large fields. Micro-irrigation is a system that distributes water under low pressure through a piped network and applies it as a small discharge to each plant. Drip irrigation delivers water directly to the root zone of plants. This method can be the most water-efficient method of irrigation if managed properly; evaporation and runoff are minimized. The field water efficiency of drip irrigation is typically in the range of 80 to 90% when managed correctly. In sprinkler irrigation, water is piped to one or more central locations within the field and distributed by overhead high-pressure water devices. Center pivot irrigation is a form of sprinkler irrigation utilizing several segments of pipe joined and supported by trusses, mounted on wheeled towers with sprinklers positioned along its length. These systems move in a circular pattern and allow irrigation of all types of terrain. Subirrigation has been used for many years in field crops in areas with high water tables. It is a method of artificially raising the water table to allow the soil to be moistened from below the plants' root zone.
When did the earliest known use of irrigation technology begin in Khuzistan?
The earliest known use of irrigation technology dates to the 6th millennium BCE in Khuzistan in the south-west of Iran. The site of Choga Mami, located in present-day Iraq on the border with Iran, is believed to be the earliest to show first canal irrigation in operation at about 6000 BCE.
What are the main types of surface irrigation systems used today?
Surface irrigation, also known as gravity irrigation, moves water across agricultural lands by following gravity or the slope of the land. This method involves significantly lower capital cost and energy requirements than pressurized irrigation systems, making it a common choice for developing nations and large fields.
Which countries have the largest equipped area for irrigation globally?
India with 76 million hectares and China with 75 million hectares have the largest equipped area for irrigation worldwide. These two nations far exceed the United States of America, which has 27 million hectares of irrigated land.
How does over-irrigation affect groundwater and soil quality?
Over-irrigation can lead to permanent loss of aquifer capacity, decreased water quality, ground subsidence, and salinization of crops. Projects that pump too much from underground aquifers create subsidence and allow salt to seep into drinking water while damaging agricultural output.
When did Congress pass the National Reclamation Act regarding western US irrigation projects?
Congress passed the National Reclamation Act in 1902 to channel money from the sale of western public lands into irrigation projects on public or private land in the arid West. This legislation facilitated the development of infrastructure to support agriculture in regions like Arizona, Colorado, and Nevada.
In 2000, the total fertile land was 2,788,000 km2 (689 million acres), and it was equipped with irrigation infrastructure worldwide. Roughly 68% of this area is in Asia, 17% in the Americas, 9% in Europe, 5% in Africa and 1% in Oceania. By 2012, the area of irrigated land had increased to an estimated total of 3,242,917 km2 (801 million acres). The scale of global irrigation increased dramatically over the 20th century. In 1800, 8 million hectares globally were irrigated, in 1950, 94 million hectares, and in 1990, 235 million hectares. By 2021 the global land area equipped for irrigation reached 352 million ha, an increase of 22% from the 289 million ha of 2000. India (76 million ha) and China (75 million ha) have the largest equipped area for irrigation, far ahead of the United States of America (27 million ha). The vast majority is located in Asia (70%), where irrigation was a key component of the green revolution. The irrigation of 20% of farming land accounts for the production of 40% of food production. All the regions saw increases in the area equipped for irrigation, with Africa growing the fastest (+29%), followed by Asia (+25%), Oceania (+24%), the Americas (+19%) and Europe (+2%). Countries frequently invested in irrigation to increase wheat, rice, or cotton production, often with the overarching goal of increasing self-sufficiency.
Environmental Consequences And Risks
Negative impacts frequently accompany extensive irrigation. Some projects which diverted surface water for irrigation dried up the water sources, which led to a more extreme regional climate. Projects that relied on groundwater and pumped too much from underground aquifers created subsidence and salinization. Salinization of irrigation water in turn damaged the crops and seeped into drinking water. Pests and pathogens also thrived in the irrigation canals or ponds full of still water, which created regional outbreaks of diseases like malaria and schistosomiasis. In the mid-20th century, the advent of diesel and electric motors led to systems that could pump groundwater out of major aquifers faster than drainage basins could refill them. This can lead to permanent loss of aquifer capacity, decreased water quality, ground subsidence, and other problems. The future of food production in such areas as the North China Plain, the Punjab region in India and Pakistan, and the Great Plains of the US is threatened by this phenomenon. Overirrigation because of poor distribution uniformity or management wastes water, chemicals, and may lead to water pollution. Deep drainage from over-irrigation may result in rising water tables which in some instances will lead to problems of irrigation salinity requiring watertable control by some form of subsurface land drainage. For example, in Australia, over-abstraction of fresh water for intensive irrigation activities has caused 33% of the land area to be at risk of salination.
Historical Case Studies In Policy
In the lower Colorado Basin of Arizona, Colorado, and Nevada, the states derive irrigation water largely from rivers, especially the Colorado River, which irrigates more than 4.5 million acres of land. Only in 1902 did Congress pass the National Reclamation Act, which channeled money from the sale of western public lands into irrigation projects on public or private land in the arid West. When the Bolsheviks conquered Central Asia in 1917, the native Kazakhs, Uzbeks, and Turkmens used minimal irrigation. The Soviet irrigation push stemmed mainly from their late 19th century fears of the American cotton monopoly and subsequent desire to achieve cotton self-sufficiency. Before diversion, the Syr Darya and Amu Darya rivers delivered 56 cubic kilometers of water to the Aral Sea per year, but after diversion they only delivered 15 cubic kilometers. By 1975, the USSR used eight times as much water as they had in 1913, mostly for irrigation. Irrigated hectares in Central Asia capped out at 7 million. Mikhail Gorbachev killed a proposed plan to reverse the Ob and Yenisei for irrigation in 1986. In Egypt, modern irrigation began with Muhammad Ali Pasha in the mid-1800s, who sought to achieve Egyptian independence from the Ottomans through increased trade with Europe. His administration proposed replacing the traditional Nile basin irrigation with irrigation barrages in the lower Nile. Egypt devoted 105,000 ha to cotton in 1861, which increased fivefold by 1865.
Water Scarcity And Future Challenges
Until the 1960s, there were fewer than half the number of people on the planet as of 2024. People were not as wealthy as today, consumed fewer calories and ate less meat, so less water was needed to produce their food. They required a third of the volume of water humans presently take from rivers. Today, the competition for water resources is much more intense, because there are now more than seven billion people on the planet. This creates increasing competition for water from industry, urbanisation and biofuel crops. Farmers will have to strive to increase productivity to meet growing demands for food, while industry and cities find ways to use water more efficiently. Irrigation water can come from non-conventional sources like treated wastewater, desalinated water, drainage water, or fog collection. In countries where humid air sweeps through at night, water can be obtained by condensation onto cold surfaces. This is practiced in the vineyards at Lanzarote using stones to condense water. A Glasgow-based startup has helped a farmer in Scotland to establish edible saltmarsh crops irrigated with sea water. An acre of previously marginal land has been put under cultivation to grow samphire, sea blite, and sea aster; these plants yield a higher profit than potatoes.