About 75 percent of irrigated cropland in the United States is located in the 17 western-most contiguous States, based on USDA’s 2013 Farm and Ranch Irrigation Survey (the most recent available). Between 1984 and 2013, while the amount of irrigated land in the West has remained fairly stable (at about 40 million acres) and the amount of water applied has been mostly flat (between 70 and 76 million acre-feet per year), the use of more efficient irrigation systems to deliver the water has increased.
In 1984, 71 percent of Western crop irrigation water was applied using gravity irrigation systems that tend to use water inefficiently. By 2013, operators used gravity systems to apply just 41 percent of water for crop production, while pressure-sprinkler irrigation systems (including drip, low-pressure sprinkler, or low-energy precision application systems), which can apply water more efficiently, accounted for 59 percent of irrigation water use and about 60 percent of irrigated acres.
This chart is found in the ERS topic page on Irrigation & Water Use, updated October 2015.
Source:usda.gov