Agriculture is a major user of ground and surface water in the United States, accounting for approximately 80 percent of the Nation’s consumptive water use (see definitions) and over 90 percent in many Western States. Efficient irrigation systems and water management practices can help maintain farm profitability in an era of increasingly limited and more costly water supplies. Improved on-farm water management, combined with institutional measures improving watershed-scale water-management, including the use of conserved water rights, dry-year water banks, option water markets, and regulated irrigation withdrawals, may also reduce the impact of irrigated production on offsite water quality while conserving water for growing non-agricultural demands.
The effectiveness of agricultural conservation programs in supporting water conservation and environmental policy goals may vary with local hydro-logic conditions; the type, size, and location of irrigated farms; and the legal and institutional measures governing water use. The ERS research, data, and information program investigates water allocation, conservation, and management issues associated with water scarcity challenges facing irrigated agriculture in a changing water environment. Topics examined include the following:
- The value of irrigated agriculture to U.S. agriculture, where it occurs, and what it produces;
- Adoption of irrigation technologies and water-management practices, and resulting cost, resource use, and water quality implications;
- USDA farm conservation program investments supporting improved irrigation water management;
- Water-related policies affecting resource allocation and use, water cost, commodity production, farm profitability, and environmental quality; and
- Producer and sector adaptation to increasing water scarcity due to competing demands, drought, and long-term climate change.
Data are available in the ERS product Western Irrigated Agriculture, which summarizes the farm-structural characteristics for irrigated farms in the 17 Western States based on USDA’s 2008 Farm and Ranch Irrigation Survey (with results from the 1998 survey also included).
Definitions: Withdrawal, Applied, and Consumptive Water-Use Estimates
U.S. Geological Survey water use estimates generally refer to withdrawals, or the quantity of water withdrawn from a water source—e.g., a river, lake, or aquifer. USDA Farm & Ranch Irrigation Survey (FRIS) reports on-farm applied water use, referring to producer estimates of the quantity of water applied to the field (for a particular crop) via an on-farm irrigation application system—e.g., a gravity-flow system or a low-pressure center-pivot sprinkler system. Annual crop consumptive-use estimates refer to the quantity of water actually consumed (taken up) by the crop plant over its various crop-growth stages for crop retention and evapo-transpiration. Withdrawal estimates generally reflect diversion system conveyance losses, while estimates of field water applied do not. Consumptive-use estimates may or may not account for associated system efficiency losses (e.g., evaporation, deep percolation, and runoff) and salt-leaching requirements for a given crop, location, and irrigation system. Which estimate to use and how to use it are important in clarifying discussions of water use and policy.