Irrigation Methods: Furrow or Flood Irrigation

Science Center Objects

It's a good thing farmers don't need to haul buckets of water to keep crops watered. Nearly as old as the bucket method though, is furrow or flood surface irrigation where farmers flow water down small trenches running through their crops. For more information about irrigation read on. 

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Corn Irrigation - Mississippi

Flood irrigation of corn crops in Mississippi.

Probably one of the oldest methods of irrigating fields is surface irrigation (also known as flood or furrow irrigation), where farmers flow water down small trenches running through their crops. Humans' first invention after learning how to grow plants from seeds was probably a bucket. Ancient people must have been strong from having to haul buckets full of water to pour on their first plants. For most of human history, people did not have mechanized spray irrigation systems to apply water to crop fields. It was more like, "Hey, Big Guy, take this reed bucket and go down to the river and fill 'er up."

Surface irrigation is still used today throughout the world,especially in less-developed areas where mechanical techniques are not available. In fact, 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. Flood irrigation is not the most efficient irrigation method, but it is cheap and low-tech. On the one hand, less water is lost to evaporation than in spray irrigation, but on the other hand, more water can be lost from runoff at the edges of the fields.

Here are some more-efficient surface-irrigation techniques that farmers use:

  1. Leveling of fields: Flood irrigation uses gravity to transport water, and, since water flows downhill, it will miss a part of the field that is on a hill, even a small hill. Farmers are using leveling equipment, some of which is guided by a laser beam, to scrape a field flat before planting. That allows water to flow evenly throughout the fields. (Actually, this method of levelling a field is also used to build flat tennis courts).
  2. Surge flooding: Traditional flooding involved just releasing water onto a field. In using surge flooding, water is released at prearranged intervals, which reduces unwanted runoff.
  3. Capture and reuse of runoff: A large amount of flood-irrigation water is wasted because it runs off the edges and back of the fields. Farmers can capture the runoff in ponds and pump it back up to the front of the field where it is reused for the next cycle of irrigation.

 

Flood/furrow irrigation water use in the United States, 2015

Irrigation is one of the major uses of water throughout the world. In the United States in year 2015, irrigation withdrawals were an estimated 118,000 million gallons per day (Mgal/d), or 132,000 thousand acre-feet per year. About 63,500 thousand acres were irrigated in 2015. Of this total acreage, about 23,300 thousand acres with flood/furrow systems.

 

Irrigation methods