Quick Study: How Will Climate Change Affect Irrigation of Farm Lands in U.S.?

irrigation of corn fields

Irrigation of corn fields. Photo by flickr user justcallme Johnny via a Creative Commons license.

Quick Study is just what it says — a rapid-fire look at a new conservation science study that might turn some heads.

The Study: McDonald, R. and E. Girvetz. 2013. Two challenges for U.S. irrigation due to climate change: increasing irrigated area in wet states and increasing irrigation rates in dry statesPLoS ONE 8(6): e65589. doi:10.1371/journal.pone.0065589.

The Questions: Climate change models forecast higher average temperatures that will cause crop-growing seasons in the United States to become hotter and drier. How will this impact the irrigation needs of agriculture in the United States? And how will farmers respond to drier conditions?

Study Nuts and Bolts: The authors (both Nature Conservancy scientists) looked at how farmers use of irrigation varied in response to weather changes over a 20-year period (1985-2005). The researchers calibrated data on farmers’ responses to moisture deficit (the shortfall of water needed for crops) with future climate change trends through 2090, using 16 GCMs (global circulation models) for climate change under various emissions scenarios.

What They Found: Climate change will bring increased moisture deficits across the United States, with the largest deficits in the South and Southwest. These deficits will produce two key changes in U.S. agriculture: Arid or “dry” states (such as Montana, Idaho and Colorado) will need to increase the amount of water needed for irrigation, while “wet” states (ie, Kansas and Texas) will need to start irrigating areas that are currently rain-fed. Nationally, the average amount of water needed for irrigation will go from 850,000 gallons/acre to 898,000 –1,110,000 gallons/acre in 2090 (an increase of 5-30%) and the total area irrigated will increase by 11-54 million acres (an increase of 19-94%).

However, the authors also note a historical trend toward greater irrigation efficiency — a trend that, if it continues, could offset most of the predicted future demands on irrigation.

What Does It All Mean? Agriculture in the United States will need to adapt to future conditions: Places that are already irrigating are going to need to increase the amount of water they’re using, and places that aren’t irrigating much now will need to irrigate more areas. States that need to start irrigating face the biggest challenges: They are not currently set up for complicated water rights management like the more arid states, and are also not providing incentives for farmers to improve irrigation efficiency.

The authors also call attention to the role of reducing emissions: By avoiding the release of 1 GtC, the U.S. can save roughly 17 billion gallons in irrigation water annually.

For more insights, read study author Rob McDonald’s blog about how farmers will adapt.

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Opinions expressed on Cool Green Science and in any corresponding comments are the personal opinions of the original authors and do not necessarily reflect the views of The Nature Conservancy.

Darci Palmquist is a senior science writer for The Nature Conservancy. Previously she served as editorial manager for nature.org, the website of The Nature Conservancy, as well as for the Conservancy's e-newsletter. She is based in Amherst, Massachusetts.




Comments: Quick Study: How Will Climate Change Affect Irrigation of Farm Lands in U.S.?

  •  Comment from Donald Shult

    Hi! How will climate change and farm irrigation systems effect the aquafirs and our well systems in central Illinois?

  •  Comment from Rob McDonald

    Hi Donald,

    The short answer is that our national level study isn’t detailed enough to give you specific forecasts of what is going to happen in your aquifer in central Illinois. All our national study can say is that in places like Illinois, we expect farmers to attempt to increase their water use significantly, given the drier climate.

    You might try asking the local ag extension folks to see if they know of any one doing more detailed work on groundwater in Illinois. It strikes me that someone is probably doing this work, but I don’t know who to connect you to.

    Cheers,
    Rob

  •  Comment from Ann Bleed

    One must be careful when talking about irrigation efficiency as a way of solving water deficit problems. In many cases increased irrigation efficiency means the increased consumptive use of water, that is an increase in evaporation and evapotranspiration, which removes water from the local area. When increased efficiency in the use of water decreases the non-beneficial consumptive use of water, efficiency can be a benefit. Also it is true increased water-use efficiency does usually correlate with increased crop production, which is a benefit in the short term. However, we must not forget that increased water-use efficiency usually means an increase in the consumptive use of water and in many areas, this increased water consumption means less water for other uses and less water for future generations.

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