

The flowing water of a river has great power to carve and shape the landscape. Many of the largest rivers empty into the ocean. Here, the river empties into another body of water-a larger river, a lake, or the ocean. A river’s watershed includes the river, all its tributaries, and any groundwater resources in the area. A river system is also called a drainage basin or watershed.

Together, a river and its tributaries make up a river system. For instance, the Amazon River receives water from more than 1,000 tributaries. It is also fed by other streams, called tributaries. Precipitation and groundwater add to the river’s flow. From its source, a river flows downhill as a small stream. The source of the Danube River is a spring in the Black Forest of Germany. A spring bubbling out of the ground can also be the headwaters of a river. state of Minnesota, the source of the Mississippi River. A river’s source could be a lake with an outflowing stream, such as Lake Itasca in the U.S. The source could be melting snow, such as the snows of the Andes, which feed the Amazon River. The source may be a melting glacier, such as the Gangotri Glacier, the source of the Ganges River in Asia. The beginning of a river is called its source or headwaters. Yet all rivers have certain features in common and go through similar stages as they age. Anatomy of a River No two rivers are exactly alike. The water cycle constantly replenishes Earth’s supply of freshwater, which is essential for almost all living things. The movement of water between land, ocean, and air is called the water cycle. This freshwater feeds rivers and smaller streams. Clouds carry moisture over land and release it as precipitation. One of the most important things they do is carry large quantities of water from the land to the ocean. Approximately one-fifth of all the freshwater entering the oceans comes from the Amazon. There is no debate, however, that the Amazon carries m ore water than any other river on Earth. The Nile is estimated to be between 5,499 kilometers (3,437 miles) and 6,690 kilometers (4,180 miles) long. The Amazon is estimated to be between 6,259 kilometers (3,903 miles) and 6,800 kilometers (4,225 miles) long.

Also, the length of rivers can change as they meander, are dammed, or their deltas grow and recede. Measuring a river is difficult because it is hard to pinpoint its exact beginning and end. For centuries, scientists have debated which river is longer. The longest rivers in the world are the Nile in Africa and the Amazon in South America. A river may be only kilometers long, or it may span much of a continent. Others flow seasonally or during wet years. Rivers are found on every continent and on nearly every kind of land. A river is a large, natural stream of flowing water.
