What is irrigation?
Irrigation is a method of supplying water to crops artificially. It was used in ancient Egypt, and possibly even earlier. Water is pumped out of rivers or wells and fed into channels or canals that carry it for long distances. Modern irrigation systems are usually very extensive.
Elaborate irrigation was used centuries ago in some parts of the world. Native Americans cut long canals along the foot of the Andes to irrigate their crops, which they grew on artificial terraces. Even today, many Asian hillsides are covered with flooded terraces where rice is grown. The terraces are irrigated by complicated canal systems.
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How do dams affect the environment?
Most dams are built to meet people’s growing demand for water, but sometimes dams cause unforeseen environmental damage. Dams are usually built across valley entrances, creating enormous reservoirs of water. Some are built to provide water for hydroelectric power stations while others control the flow of rivers that are liable to flood. Unfortunately, the best places to build dams are usually in the most picturesque parts of the countryside.
The Aswan High Dam was built to control the flow of the River Nile. However it has prevented the river’s annual flooding, which covered agricultural land with silt.
Picture credit: google