Irrigation in the United States

Irrigation in the United States is the deliberate delivery of water to agricultural land. Its methods and scale vary with regional climates, water sources, crops, and infrastructure.

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Center-pivot irrigation: A mechanized irrigation system that rotates a sprinkler pipeline around a central point. Its circular fields are a distinctive feature of irrigated farming across the Great Plains.
Ogallala Aquifer: A vast aquifer beneath parts of the Great Plains that supplies water to farms and communities. It underpins extensive irrigation in a region with limited rainfall.
Groundwater depletion in the United States: The decline of groundwater reserves caused when withdrawals exceed replenishment. Persistent pumping for irrigation has lowered water tables in major farming areas.
Rain-fed agriculture: Crop production that relies primarily on precipitation rather than water applied through irrigation. It distinguishes farms whose yields depend on rainfall from those supported by managed water.
Drip irrigation: A method that delivers water slowly near plant roots through pipes and emitters. It reduces evaporation and runoff where water is scarce or valuable.
California Central Valley: A fertile agricultural region in California between the Coast Ranges and Sierra Nevada. Its crops depend on a combination of local groundwater, rivers, and imported water.
Salinization: The accumulation of soluble salts in soil or water to levels that impair plants or ecosystems. Irrigation in dry climates can leave salts behind as water evaporates.
Dryland farming: Crop production in arid or semiarid regions using soil-moisture conservation rather than routine irrigation. It shows how farmers can adapt to limited water without building irrigation systems.
Surface irrigation: An irrigation method that moves water across fields by gravity, through furrows, basins, or borders. Gravity-fed field systems remain common in major western irrigated regions.
Colorado River: A major river of the southwestern United States and northwestern Mexico, heavily managed for water supply. Its reservoirs and diversions support farms in an arid multistate basin.