Farmers obtain most of the water for their crops from rain. Rain water that is not absorbed by the soil and plant roots runs into streams and rivers. ... Farmers in areas where there is not enough rain for their crops to grow must irrigate their fields.
Most likely, the first irrigation methods consisted of bringing buckets of water from wells or rivers and pouring it on their crops. Irrigation systems of the modern era supply crops with water from reservoirs, tanks, and wells.
