Note: This story is embargoed for republication until Nov. 24, 2019
Efficient irrigation may produce more crops, but it doesn’t appear to preserve groundwater, according to a federal report released this week.
Decades of irrigation has already depleted aquifers that many irrigated farms rely on, according to the report from the Government Accountability Office, and efficient systems appear to not help.
Minus a few exceptions, GAO researchers found “there is no change in the amount of water farmers apply to a field with more efficient technology,” according to the Nov. 12 report.
In 2015, irrigation used between 20 trillion and 30 trillion gallons of water, mostly in the West. Overall, irrigation uses 40 percent of freshwater.
According to the report, freshwater both surface water and groundwater – such as the water in lakes and rivers (surface water) and aquifers (groundwater).
Generally, efficient irrigation means using less water to produce similar crop yields as conventional irrigation.
Farms that employ efficiencies may be applying less water to crops, but there appears to be no overall effect on groundwater resources because much of the water used evaporates or slips into surface water, according to the report.
The report noted that efficient irrigation technology may have unintended consequences. Farmers may increase the amount of acres they irrigate or switch to crops that require more water.
“These unintended consequences would result in more water going towards crop production —more consumptive use of water,” according to the report.
The report identified areas in the U.S. with high-levels of irrigation that also have a scarcity of water: primarily Nebraska and Kansas, southeastern Idaho and central California.
Nebraska has millions of acres of irrigated farmland, but the source of its groundwater has been drawn down — likely past the point of sustainability.
In 2017, Nebraska had more irrigated acres than any other state, about 8.5 million, or about 15 percent, according to the latest USDA Census of Agriculture figures.
A primary source of its groundwater is the High Plains, or Ogallala, aquifer, which dropped 15.8 feet between 1950 and 2015, according to a 2017 U.S. Geological Survey analysis.
“The rate of groundwater withdrawal for irrigation in the Ogallala Aquifer far exceeds the rate of natural recharge, resulting in large groundwater depletions,” read the GAO report.
(Nebraska farmers have dealt with floods this year, and, in a twist, found themselves without water this summer because an irrigation tunnel collapsed during harvest season, according to The New York Times.)
California had the second-most irrigated acres in 2017, at about 7.8 million, or 13.5 percent, according to the agricultural census.
It has also dealt with decreased amounts of groundwater. Recently, the 2013-2016 drought led to overdrafts of groundwater, “primarily due to withdrawals for irrigation,” according to the GAO report.
In our “Uncharted Waters” series, we looked at irrigation’s effect on water in Illinois. We found that, as demand for water increases across the state, irrigation could likely lead to a water crunch.
But Illinois isn’t the only state facing this.
In a 2014 report, the GAO surveyed state water managers, and 40 said they expected water shortages in some areas of their state in a decade.
This story was updated on Nov. 18, to include a definition of freshwater.
Sky Chadde is the 2019 GateHouse Agriculture Data Fellow based at the Midwest Center for Investigative Reporting. Reach him at firstname.lastname@example.org