Sources of Irrigation Water
Sources of irrigation water can be groundwater extracted from springs or by using wells, surface water withdrawn from rivers, lakes or reservoirs or non-conventional sources like treated wastewater, desalinated water or drainage water. A special form of irrigation using surface water is spate irrigation, also called floodwater harvesting. In case of a flood (spate) water is diverted to normally dry river beds (wadis) using a network of dams, gates and channels and spread over large areas. The moisture stored in the soil will be used thereafter to grow crops. Spate irrigation areas are in particular located in semi-arid or arid, mountainous regions. While floodwater harvesting belongs to the accepted irrigation methods, rainwater harvesting is usually not considered as a form of irrigation. Rainwater harvesting is the collection of runoff water from roofs or unused land and the concentration of this. Some of Ancient India's water systems were pulled by oxen.
Around 90% of wastewater produced globally remains untreated, causing widespread water pollution, especially in low-income countries. Increasingly, agriculture is using untreated wastewater as a source of irrigation water. Cities provide lucrative markets for fresh produce, so are attractive to farmers. However, because agriculture has to compete for increasingly scarce water resources with industry and municipal users (see Water scarcity below), there is often no alternative for farmers but to use water polluted with urban waste, including sewage, directly to water their crops. There can be significant health hazards related to using water loaded with pathogens in this way, especially if people eat raw vegetables that have been irrigated with the polluted water. The International Water Management Institute has worked in India, Pakistan, Vietnam, Ghana, Ethiopia, Mexico and other countries on various projects aimed at assessing and reducing risks of wastewater irrigation. They advocate a ‘multiple-barrier’ approach to wastewater use, where farmers are encouraged to adopt various risk-reducing behaviours. These include ceasing irrigation a few days before harvesting to allow pathogens to die off in the sunlight, applying water carefully so it does not contaminate leaves likely to be eaten raw, cleaning vegetables with disinfectant or allowing fecal sludge used in farming to dry before being used as a human manure. The World Health Organization has developed guidelines for safe water use.
Read more about this topic: Irrigation
Famous quotes containing the words sources of, sources and/or water:
“Even healthy families need outside sources of moral guidance to keep those tensions from imploding—and this means, among other things, a public philosophy of gender equality and concern for child welfare. When instead the larger culture aggrandizes wife beaters, degrades women or nods approvingly at child slappers, the family gets a little more dangerous for everyone, and so, inevitably, does the larger world.”
—Barbara Ehrenreich (20th century)
“The American grips himself, at the very sources of his consciousness, in a grip of care: and then, to so much of the rest of life, is indifferent. Whereas, the European hasn’t got so much care in him, so he cares much more for life and living.”
—D.H. (David Herbert)
“I think of the nestling fallen into the deep grass,
The turtle gasping in the dusty rubble of the highway,
The paralytic stunned in the tub, and the water rising,—
All things innocent, hapless, forsaken.”
—Theodore Roethke (1908–1963)