The process of artificially watering crops is called irrigation. In some areas of the world, agriculture can rely on rainfall for all its water needs. In drier areas (usually those receiving less than 20 inches [51 centimeters] of rainfall per year), irrigation is required. Water is pumped from aquifers or delivered via an aqueduct to the fields where it flows through small channels between plants, or is sprayed through sprinklers. In very water-conservative regions such as Israel, water is scientifically dripped onto plants, thereby providing the exact amount of water necessary.