GAO

Irrigated Agriculture
Technologies, Practices, and Implications for Water Scarcity

Nationwide, 20-30 trillion gallons of water/year are consumed by irrigation.

In this map of the Water Stress Index, darker orange indicates more water consumed relative to water available. Black indicates irrigated areas.

Several areas are heavily irrigated and considered water stressed, such as areas of California, Nebraska, and Kansas.

Water Stress Index
Low (<10%)
Low to medium (10-20%)
Medium to high (20-40%)
High (40-80%)
Extremely high (>80%)
Arid and low water use
Irrigated area

Source: GAO analysis of data from World Resources Institute Aqueduct, accessed on Feb. 21, 2018, and Moderate Resolution Imaging Spectroradiometer Irrigated Agriculture Dataset for the United States for 2012.

Three types of irrigation vary in efficiency.
1. Gravity
Most water usage

2. Sprinkler
Less water usage

3. Micro irrigation
Least water usage

Top crops, by acreage, irrigated by each system in 2013.
Gravity: Soybeans, rice
Sprinkler: Corn, soybeans
Micro irrigation: Orchards, vegetables

Source: GAO.

Will more efficient technology save water?
Maybe. We found that farms may use more efficient irrigation technology to:
-	irrigate more land,
-	increase yield, or 
-	switch to crops that need more water.
So, more efficient irrigation doesn't always reduce water use.

Acres irrigated under sprinkler and micro irrigation compared to gravity, for the 17 western states

Irrigated Acres (in millions)  

1998
Sprinkler and Micro irrigation - 21,408,009; Error bar - 577,965.3
Gravity - 21,294,211; Error bar - 81,5078.8

2003
Sprinkler and Micro irrigation - 24,161,571; Error bar - 62,2205.2
Gravity - 17,046,418; Error bar - 43,2629.3

2008
Sprinkler and Micro irrigation - 26,958,154; Error bar - 66,0567.3
Gravity - 14,827,695; Error bar - 39,5004.2

2013
Sprinkler and Micro irrigation - 29,732,838; Error bar - 67,4721.3
Gravity - 13,293,422; Error bar - 43,2752.3

Source: GAO analysis of USDA Farm and Ranch Irrigation Survey data.

Policy options for conserving water.

The full report describes two options for federal policymakers to consider. These would likely need to be used in conjunction with appropriate agreements to conserve water.

1. Promote the use of more efficient irrigation technology and practices. 
2. Promote the use of precision agriculture, which uses data to match irrigation to crop water needs, and optimizes the use of more efficient irrigation technology and practices. 

For more information,
see GAO-20-128SP at GAO.gov 
This work has been released into the public domain.
GAO