Rivers and river valleys have been very important in the development of civilization.  A river is a moving body of water that usually has its source in an area of high ground.  An example would be the Ganges River flowing out of the Himalaya Mountains in India.  Rivers often flow to a larger body of water such as a lake, ocean, or sea.  The Nile River in Egypt flows into the Mediterranean Sea.  The end of a river is called its mouth, and with some rivers, such as the Nile, deposits of silt build up creating what is called a Delta.  A river's delta area is very important to humans as the deposits of rich silt provide very fertile farmland.

Over time, many rivers have carved out river valleys as they flow.  Early civilizations formed in these river valleys because they provided a water source, good farmland, and a source of trade.  Civilizations such as Egypt on the Nile, Mesopotamian cultures on the Tigris and Euphrates, Early China on the Huang/Yellow and the Yangtze Rivers, and Early Indian civilization on the Indus all benefited from the river's resources. Many early civilizations developed irrigation systems to further take advantage of the river.  This adaptation allowed these civilizations to grow and flourish. 

In modern times, other technologies have been developed to also make use of the river.  The Aswan High Dam on the Nile provides Egypt with a hydroelectric power source that is beneficial to the country. It also has allowed the Egyptians to reclaim many acres of land lost to desertification.  Careful management of this resources has created more arable farmland, and provided a source of life to the people in the region.  In China, the Three Gorges Dam on the Yangtze River, currently under construction, will be the largest dam ever constructed, and will provide China with power for years to come. However, opposition to the dam and the rising problems with its construction may keep this project from ever being completed.  Many environmental groups worry over the damage done to the Yangtze River Valley.