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.