How Important is Irrigation to U.S. Agriculture?
Irrigated agriculture makes a significant contribution to the
value of U.S. agricultural production, but also accounts for the
largest share of the Nation's consumptive water use. In 2007,
irrigated farms accounted for 55 percent of the total value of crop
sales while also supporting the livestock and poultry sectors
through irrigated production of animal forage and feed crops.
Roughly 57 million acres--or 7.5 percent of all U.S. cropland and
pastureland--were irrigated in 2007, nearly three-quarters of which
are in the 17 western-most contiguous States (referred to as the
western States hereafter). From 2002 to 2007, irrigated acres
increased by nearly 1.3 million acres across the U.S., with
Nebraska accounting for nearly a million additional acres. In
recent decades, however, much of the expansion in irrigated acreage
has occurred in the eastern States, particularly Arkansas and
Florida. USDA's Farm & Ranch Irrigation Survey (FRIS) reports
that in 2008, irrigated agriculture applied 91.2 million acre-feet
of water (1 acre-foot is equivalent to 325,851 gallons), with over
four-fifths of applied water occurring in the West. The U.S.
Geological Survey, which monitors water use by economic sector,
estimates that irrigated agriculture accounted for 37 percent of
the Nation's freshwater withdrawals in 2005. Agriculture, however,
accounts for approximately 80-90 percent of U.S. consumptive water
use.
Challenges for Agriculture Under a Changing Water
Environment
Population and economic growth, Native American water-right
claims, and water quality/environmental priorities are increasing
the demand for water resources. Expansion of the U.S. energy sector
is also expected to increase regional demands for water. In much of
the West where irrigation is concentrated, climate change could
shrink water supplies as a result of warming
temperatures, shifting precipitation patterns, and reduced
snowpack, while also increasing water demand. These trends place
added pressure on existing water allocations, heightening the
importance of water conservation for a sustainable irrigated
agriculture sector.
The future of irrigated agriculture will depend in part on the
ability of producers to improve on-farm water management for crop
production. Upgrades in irrigation system technologies and
improved water-management practices can enhance on-farm water-use
efficiency. In addition, coordinating water management at the farm-
and watershed-levels may help increase the efficiency of water
allocations among competing users. Institutional measures--such as
conserved water rights, groundwater and surface-water withdrawal
restrictions, drought water banks, and option water markets--can
encourage agricultural producers to reduce crop consumptive use
while facilitating the reallocation of water to higher valued uses.
On-Farm Irrigation Efficiency: Opportunities for Continued
Improvement
Water-use efficiency gains provide not only farm-level benefits,
but can contribute to off-farm benefits as well, including improved
fish and wildlife habitat, and reduced ecosystem and human health
risks associated with environmental degradation. On-farm irrigation
efficiency--the share of applied water that is beneficially used by
the crop--has increased in recent decades. FRIS survey data reveal
a shift to more efficient irrigation systems, reducing average
per-acre applied water rates across crops and regions. The
efficiency of irrigation systems is particularly important in the
arid western States where water demand for agriculture is greatest,
and where increases in competing demands and climate change impacts
are expected to affect water supplies for agriculture. In 1984,
gravity systems--which used roughly 54 percent more water per acre
than pressurized systems, on average--accounted for more than 70
percent of all water applied for crop agriculture in the West. By
2008, gravity systems applied less than half of all western
irrigation water. At the same time, continued efficiency advances
were achieved with both gravity and pressure systems. By 2008,
fewer acre-feet of water were required to irrigate a greater number
of acres, reflecting improved water-use efficiency, as well as
changes in irrigated acreage distributions and regional cropping
patterns. From 1984 to 2008, total irrigated farmland in the West
increased by 2.1 million acres, while water applied declined by
nearly 100,000 acre-feet. In 2008, applied water rates in the
region averaged 2.4 acre-feet per acre for gravity systems and 1.4
acre-feet for pressure systems.
While substantial technological innovation has already occurred
in U.S. irrigated agriculture, additional water-use efficiency
gains are achievable. The chart below shows 1994-2008 changes, in
the share of Western irrigated acres using more efficient
irrigation systems. More than half of irrigated cropland acres in
the West continue to be irrigated with more traditional,
less-efficient application systems. In addition, FRIS data indicate
that the potential exists for increased irrigation efficiency
through more extensive use of improved on-farm water-management
practices. Fewer than 10 percent of irrigators made use of soil- or
plant-moisture sensing devices or commercial irrigation scheduling
services in 2008. Fewer than 2 percent used computer-based
simulation models to determine irrigation requirements based on
consumptive-use needs by crop-growth stage under local weather
conditions.
Private and Public Investment in Irrigation Improvements
Irrigators continue to make significant capital investments in
irrigation equipment and infrastructure. Approximately $2.15
billion was spent on irrigation systems (beyond expenditures for
maintenance and repair) on U.S. farms in 2008. Nearly three-fourths
of these capital investments were on land in the West, where the
vast majority of irrigated land is located.
The majority of U.S. irrigation investment is financed
privately; fewer than 10 percent of farms reporting irrigation
improvements in 2003 or 2008 received public financial assistance.
Over half of the farms receiving public assistance for irrigation
investments made use of USDA's Environmental Quality Incentives
Program (EQIP), though these farms represented less than 5 percent
of all irrigated farms that made irrigation investments in 2003 or
2008. Nonetheless, EQIP funding has had an important cumulative
impact on irrigation investments. Nationally, irrigation practices
accounted for roughly a quarter of total EQIP funding obligations
($5.7 billion) from 2004 to 2010.
The magnitude of public irrigation investment under EQIP varies
across the U.S., reflecting the relative importance of irrigation
to the regional agricultural economy as well as Federal program
funding guidelines and State contract ranking criteria. In the
western States, funding of irrigation practices as a share of total
EQIP outlays ranged from 13 percent in the Northern Plains to 58
percent for the Southern Mountain States. Irrigation practices
account for a relatively small share of program expenditures in the
eastern States. Since 2004, however, EQIP funding shares for
irrigation practices have generally increased in the eastern States
while they have declined in the West.