In an earlier post, we noted that agricultural production could be increased through extensification – more acres in production – or intensification. A rather obvious form of intensification – or increasing the output from an acre of land – is irrigation. This week’s post reviews current trends in agricultural irrigation in the United States.
Irrigated Acres Trend Higher
In 2017, the U.S. had 58 million acres of irrigated farmland. This was more than 2 million acres, or 4%, higher than reported in the 2012 Census of Agriculture (Figure 1). Throughout history, the number of irrigated acres in the U.S. has trended higher. In 1949, the U.S. had 26 million acres under irrigation. While the trend has been upward, the rate has been relatively slow, averaging an average growth rate of 1.2% annually. The Rule of 72 would imply acres irrigated in the U.S. double every 60 years.
Notice that irrigated acreage expanded rapidly during the farm boom of the 1970s before slipping during the farm financial crisis of the 1980s. More recently, acreage was an average of 55.8 million from 1997-2012, before turning higher to 58 million in 2017. This is to say, periods of high income seem to encourage additional irrigated production.
State-level Trends in Agricultural Irrigation
Beyond the upward national trend, significant variations have played out at the state level. First, 72% of irrigated acres are concentrated in just ten states (Figure 2). Acreage in Nebraska (8.6 million) and California (7.8 million) stand out as these states account for 29% of total U.S. irrigated acreage.
Figure 3 breaks down the state-level acreage changes between 2012 and 2017. Kansas and Texas stand out as irrigated acres contracted sharply. While the national trend was a net increase of nearly 2.2 million acres, these two states posted a combined contraction of 500,000 acres. On the other hand, eleven states added more than 100,000 acres each, with Missouri (+348,000) and Nebraska (+291,000) adding the most.
Sips or Gulps?
Another state-level variation is in the amount of water used. On average, the U.S. irrigated 1.5 acre-feet of water per acre in 2018. This was down from 1.6 in 2013 and 1.7 in 2008 and 2003.
At the state level, nine states exceeded the national average (Figure 4). Arizona’s irrigation rate of 4.7 acre-ft/acre was more than three times the national average. California (2.9 acre-ft/acre), Nevada (2.8 acre-ft/acre), and Washington (2.2 acre-ft/acre) also irrigate intensely. Overall, water usage on an acre basis is highest for states in the Western regions of the U.S.
Of course, these data are a single year and are subject to several factors. First, the annual rainfall could alter the need for irrigation. Additionally, crops raised and management practices vary greatly across states and regions.
Wrapping It Up
In recent years, acres of irrigation have turned higher in the U.S. The expansion is likely due to a combination of boom-era profitability and the long-run, upward trends. Furthermore, the drought of 2012 remains fresh in producers’ minds.
What’s also worth noting is that trends in agricultural irrigation vary significantly at the state level. While the U.S. has added acres of irrigation, this isn’t the case across all states. Kansas and Texas, for example, observed significant declines. Furthermore, the amount of water applied also varies across the country. Some states – due to climate and crop mix – simply apply more water than other regions.
Editor’s Note: This post was originally published in April 2015 and has been updated for accuracy and comprehensiveness.