Colorado Ag. Science Curriculum

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• Colorado Ag. Science Curriculum
• Section Plant and Soil Science
• Unit 5 - Environmental Factors
• Lesson 6
• Managing Water Irrigation

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Managing Water - Irrigation
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OBJECTIVES TO BE COVERED

1. To learn what irrigation is.
2. To learn how much water is used during irrigation
   practices.
3. To learn what type of irrigation methods are used.

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How did ancient man water his/her crops?

• Can you guess?
• A bucket!
• Ancient people must have been strong from having
  to haul buckets full of water to pour on their
  first plants.

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What is irrigation?

• Irrigation is the controlled application of water
  for agricultural purposes through manmade systems
  to supply water requirements not satisfied by
  rainfall.

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Where do the farmers get the water?

• Rivers
• Lakes
• Streams
• Reservoirs
• Wells

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How much water is used in irrigation?

• Almost 60 percent of all the world's freshwater
  withdrawals go towards irrigation uses.
• California, Idaho, Colorado, and Nebraska
  combined accounted for one-half of the total
  irrigation withdrawals in 2000.

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• Agriculture is the largest user of water due to
  irrigation.
• It takes over 1 million gallons of water a year
  to irrigate one acre of farmland in arid
  conditions.
• Most of the water used by irrigation re-enters
  the hydrologic cycle through evapotranspiration.
• Although it has only 28 of the U.S. population,
  the arid West accounts for 80 of the average
  water consumed daily due to extensive irrigation.

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Irrigation withdrawals

• For 2000, withdrawals were an estimated 137,000
  million gallons per day (Mgal/d), or 153,000
  thousand acre-feet per year.
• Irrigation withdrawals were 40 percent of total
  freshwater withdrawals and, when excluding
  thermo-electric power, 65 percent of total
  freshwater withdrawals.
• Surface water accounted for 58 percent of the
  total irrigation withdrawals and ground water was
  42 percent.
• About 61,900,000 acres were irrigated in 2000. Of
  this total acreage, about 29,400,000, acres were
  irrigated with surface (flood) systems
  28,300,000 acres with sprinkler systems and
  4,180,000 acres with micro-irrigation systems.
• Application rates were calculated by dividing
  total withdrawals by irrigated acres.
• The average application rate was 2.48 acre-feet
  per acre for the United States.

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Flood (furrow) Irrigation

• This is sometimes referred to as Surface
  Irrigation.
• Surface irrigation is still used today throughout
  the world, especially in less-developed areas
  where mechanical techniques are not available.
• Farmers flow water down small trenches running
  through their crops.
• About one-half of the water used ends up not
  getting to the crops.

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How much water is used?

• In the United States in 2000, about 29.4 million
  acres were irrigated by flood irrigation as
  compared to about 28.3 million acres irrigated by
  spray irrigation.

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Sprinkler Irrigation

• Also called center pivot, center line or wheel
  line.
• This method is more expensive than Flood
  Irrigation.
• More efficient at using water, however, water is
  lost in evaporation.
• Problems due to foliar moisture-loving diseases
  can arise if over watering occurs.

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Drip or Trickle Irrigation

• A planned irrigation system in which water is
  applied directly to the Root Zone of plants.
• This is the most expensive, but most
  water-efficient, method.
• Low-quality water (high in salts) should not be
  used, unless filtered, due to potentially
  devastating effects of clogged emitters.
• Drip irrigation is an ineffective leaching
  method.

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