Irrigation, or artificial application of water to soil, is a major consumer of the world's water supply. Close to 60% of our world's freshwater withdrawals are used in irrigation. Unfortunately, large portions of water are wasted as a result. Only half the water that we use for irrigation is actually reusable, because of the loss to evaporation, transpiration and runoffs.
Among the many irrigation techniques that are employed today, one can determine which is most efficient depending on the agriculture and soil that is applied to the particular area.
Below are some common irrigation methods.
Flood or Furrow Irrigation
This one is rather self-explanatory. The soil is flooded with water and it simply runs on gravity around the crops. Flood irrigation is the most wasteful technique, yet the most practical for underdeveloped areas because it does not require much of any equipment. In turn, it is the most common form of irrigation world wide.
Much of the water is wasted through evaporation or runoff. However farmers can prevent that by releasing the water at intervals to reduce runoff. Storing and re-using runoff, via tailwater return systems is also a possibility. Return systems essentially collect the water from runoffs in a pond for reuse in irrigation later. Leveling the farmland will also save on yield, in case there are raised areas of land that are not reached by the flood.
Source: http://www.desertusa.com/mag08/jun08/water-southwest-problems.htmlWater travels to certain points around the field and is then distributed overhead via sprinklers or guns. Common types of sprinklers include rotors (rotating sprinklers) and center pivot systems (equipment rotates around a pivot). Center pivot systems yield a distinct circular pattern of irrigated farmland, which can be viewed in the image below.
Although less wasteful than flood irrigation, water is still lost from evaporation and runoff.
Sprinkler spacing should be considered when designing the irrigation system. Having uniform water distribution can prevent over-watering and the development of diseases within the area. Below is a diagram on overhead sprinkler spacing.
Drip Irrigation
Pipes are placed directly near the plants' roots and water is trickled slowly through them. This is probably the most efficient irrigation method today because only the required amount of water for each plant is used. Drip irrigation uses up to 30% less water than a common sprinkler system. It can be adapted to uneven terrains and soil textures and wastes minimal water to evaporation, runoff or percolation, therefore making it a viable solution for areas where water is scarce or expensive. It also eliminates the need to "re-water" certain areas of a field because of inadequate distribution.
The droughts that many farmers experience are a crucial issue, because irrigation will always be a necessity. Otherwise, much of the world's farmlands would not be capable of growing crops at all. In order to conserve as much water as possible, reusing from runoffs or from rooftops are feasible solutions.
Irrigation scheduling, which refers to the use of water management techniques in order to optimize water use, yield and quality, should also be considered. Soil is an important factor in irrigation scheduling. Once soil is completely saturated with water, it will start to runoff the surface or drain beyond the root zone of the plant. In turn, dry soil may not necessarily mean that the crops need to be re-watered. Monitoring the moisture content of soil at the root zone is more accurate for determining irrigation scheduling.
The species of plant should also be considered when deciding when to irrigate. In general though, they should be watered as much as possible per irrigation session. As a result, irrigation does not have to be nearly as frequent and plants are encouraged to root deeper into the soil.
New irrigation technology is also in development. Many systems run on simple timers that switch irrigation on or off at specified time intervals. With the invention of "smart controllers", irrigation can be run based on soil moisture content, temperature and rainfall levels. Approximately 15%-30% of outdoor water use has been saved by using smart controllers.
Irrigation scheduling, which refers to the use of water management techniques in order to optimize water use, yield and quality, should also be considered. Soil is an important factor in irrigation scheduling. Once soil is completely saturated with water, it will start to runoff the surface or drain beyond the root zone of the plant. In turn, dry soil may not necessarily mean that the crops need to be re-watered. Monitoring the moisture content of soil at the root zone is more accurate for determining irrigation scheduling.
The species of plant should also be considered when deciding when to irrigate. In general though, they should be watered as much as possible per irrigation session. As a result, irrigation does not have to be nearly as frequent and plants are encouraged to root deeper into the soil.
New irrigation technology is also in development. Many systems run on simple timers that switch irrigation on or off at specified time intervals. With the invention of "smart controllers", irrigation can be run based on soil moisture content, temperature and rainfall levels. Approximately 15%-30% of outdoor water use has been saved by using smart controllers.
Sources:
"Drop Irrigation Fittings." Agriculture Guide. agricultureguide.org/agriculture/irrigation/drip-irrigation-irrigation/ (accessed November 4, 2009).
"Flood Irrigation Introduction." Alliance for Water Efficiency. http://www.allianceforwaterefficiency.org/Flood_Irrigation_Introduction.aspx (accessed November 4, 2009).
"IRRIGATION SCHEDULING TO IMPROVE WATER- AND ENERGY-USE EFFICIENCIES." Department of Biological and Agricultural Engineering @ NC State University, Raleigh, North Carolina. http://www.bae.ncsu.edu/programs/extension/evans/ag452-4.html (accessed November 4, 2009).
"Irrigation Water Conservation." Benefits of Recycling . http://www.benefits-of-recycling.com/irrigationwaterconservation.html (accessed November 4, 2009).
"Irrigation technology: Smart water solutions for state's farmers." California Farm Bureau Federation CFBF.com. http://cfbf.com/agalert/AgAlertStory.cfm?ID=1087&ck=A26398DCA6F47B49876CBAFFBC9954F9 (accessed November 4, 2009).
"Irrigation water use, from USGS Water Science.." USGS Georgia Water Science Center. http://ga.water.usgs.gov/edu/wuir.html (accessed November 4, 2009).
traditional, use of. "Irrigation: Irrigation techniques." USGS Georgia Water Science Center. http://ga.water.usgs.gov/edu/irmethods.html (accessed November 4, 2009).
-Sabrina Leung
1 responses:
Drip tape price Wow, cool post. I'd like to write like this too - taking time and real hard work to make a great article... but I put things off too much and never seem to get started. Thanks though.
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