Agricultural water use can be divided between irrigation and livestock. Irrigation includes all water applied to farm or horticultural crops; livestock incorporates water used for livestock, dairies, feedlots, fish farms, and other farm needs. Estimated annual water use for irrigation has remained at about the same level since 1985, with approximately 63% of the water used for irrigation coming from surface water. Approximately 60% of the water used for livestock comes from ground water sources and the remaining 40% from surface water sources. Combined water use for irrigation and livestock represents about 41% of total offstream freshwater use, with 40% going to irrigation and the lone 1% to livestock uses. Not only can the loss of water from irrigation conveyance systems be significant, but the percentage of consumptive water use for agriculture is high. Consumptive use is estimated at 56% for irrigation and 67% for livestock uses.

The official standard quantity of water in an acre-foot is 325,851 gallons. However, for most purposes this value is generally rounded off to 326,000 gallons. An acre-foot is the quantity of water that will cover an acre of land surface, our official land area measurement in the United States, to a depth of one foot. This term is commonly used in the U.S. because it is convenient for estimating water storage volume in lakes and reservoirs based on surface area of the particular water body and its average depth in feet. It is also a convenient term for agricultural irrigation, which is usually measured and applied as inches per acre. Of course, an acre-foot will contain 12 acre-inches of water. An acre-inch of water is equivalent to 27,154 gallons, but this value is often rounded off to 27,000. Many other water users, including municipal authorities, have adopted the acre-foot as a unit for measuring large volumes of water. City water meters are often designed to measure units of cubic feet. In looking at your water bill, you may find that your cost is based on how many units of 1000 cubic feet you used during any given month. Water use, storage and system distribution needs in cubic feet can be readily related to water supply needs in acre-feet of storage in a source reservoir. One acre-foot contains 43,560 cubic feet of water and one cubic foot contains 7.48 gallons, which is often rounded off to 7.5.

A drought is a sustained and regionally extensive occurrence of appreciably below-average natural water availability in the form of precipitation, streamflow, or groundwater. Droughts are natural events of varying duration that have occurred throughout history and they are part of the cyclical fluctuations of our planet’s climate system.

Improved efficiency can benefit senior users by reducing pumping costs, prolonging the life of aquifers, reducing waterlogging, maintaining nutrients and pesticides in the rootzone.