The USGS Water Science School
The bushes in this picture are being irrigated using the "drip irrigation" method, which is the most common type of "microirrigation." If you look closely you'll see the small horizontal pipes that are slowly dripping water running just above the ground. Drip irrigation is one of the more advanced techniques being used today because, for certain crops, it is much more efficient than traditional spray irrigation, where a larger portion of the water is lost to evaporation.
In drip irrigation, water is run through pipes (with holes in them) either buried or lying slightly above the ground next to the crops. Water slowly drips onto the crop roots and stems. Unlike spray irrigation, very little is lost to evaporation and the water can be directed only to the plants that need it, cutting back on water waste.
Microirrigation has gained attention during recent years because of its potential to increase yields and decrease water, fertilizer, and labor requirements if managed properly. Microirrigation systems can apply water and fertilizer directly to individual plants or trees, reducing the wetted area by wetting only a fraction of the soil surface; thus, water is applied directly to the root zone.
Irrigation is one of the major uses of water throughout the world. In the United States in year 2000, irrigation withdrawals were an estimated 137,000 million gallons per day (Mgal/d), or 153,000 thousand acre-feet per year. About 61,900 thousand acres were irrigated in 2000. Of this total acreage, about 28,300 thousand acres with microirrigation systems. The average application rate was 2.48 acre-feet per acre for the United States.
Data table of irrigation water use, by State, in the United States in year 2000.
Irrigation water use | Irrigation techniques | Irrigation methods
Irrigation methods: Spray | Flood | Drip | Low-energy