When the early farmers moved down from the hills into the valleys of the Nile, Tigris, and Euphrates Rivers, they had to develop the technology of irrigation. The freshwater rivers passed through lands essentially barren due to the lack of rainfall. Through irrigation, water could be removed from the rivers and spread on the nearby land, making it bloom. Ever since these early days, irrigation has been an important tool of farmers, making other deserts bloom as well. Modern examples are the very productive deserts of California.
