The United States has more than  2.9 1000000 miles of rivers.

They range from small streams and wetlands to large waterways.  No two of these rivers are the aforementioned. Each river is unique to its mural, winding through low foothills and valleys, rushing clear and cold from mountain forests, or sweeping warm and muddy downwards desert canyons.

Anatomy of A River

No affair how different our rivers are, all rivers share some basic anatomy features.

American Rivers
What parts make up a river?

Tributaries

A tributary is a river that feeds into another river, rather than ending in a lake, pond, or ocean.

If a river is large, in that location'due south a skilful run a risk that much of its water comes from tributaries. How do geographers decide which river is the "main" river and which is the "tributary" when they're naming rivers?  Usually the bigger river gets to be the "main" river, simply sometimes history or other factors come up into play.

Upwards and down, right and left

Downstream e'er points to the end of a river, or its "oral cavity." "Upstream" always points to the river's source, or "headwaters." As you lot wait downstream, your right hand corresponds to "River Right." Your left hand corresponds to "River Left." As in, "Hey, river cleanup volunteers – hither'due south a nasty tire downstream on River Left! Allow's go get information technology!"

Headwaters

The outset of a river is called its headwaters. Even if a river becomes big and powerful, its headwaters often don't start out that way. Some headwaters are springs that come from nether the basis. Others are marshy areas fed by mount snow. A river's headwaters can exist huge, with thousands of small streams that menses together, or but a trickle from a lake or swimming. What happens in the headwaters is very important to the health of the whole river, because anything that happens upstream affects everything downstream.

Channel

The shape of a river aqueduct depends on how much water has been flowing in it for how long, over what kinds of soil or rock, and through what vegetation. There are many different kinds of river channels – some are wide and constantly irresolute, some crisscross similar a complect, and others stay in one chief channel between steep banks. The bends in a river called "meanders" are acquired past the water taking away soil on the outside of a river bend and laying information technology down the inside of a river bend over time.  Each kind of river channel has unique benefits to the environment.

Riverbank

The land next to the river is called the riverbank, and the streamside trees and other vegetation is sometimes called the "riparian zone."  This is an of import, food-rich area for wild fauna, replenished by the river when it floods. In the West, these riverside areas provide habitat for more bird species than all other vegetation combined. These areas as well provide valuable services like protection from erosion during floods, and filtering polluted run-off from cities and farms.

Floodplains

Floodplains are low, flat areas next to rivers, lakes and coastal waters that periodically flood when the water is high. The animals and plants that live in a floodplain oft need floods to survive and reproduce. Salubrious floodplains benefit communities past absorbing floodwaters that would otherwise rush downstream, threatening people and property. Information technology has been estimated that restoring the 100-twelvemonth alluvion zone of the v-state Upper Mississippi River Basin could store 39 million acre-feet of floodwaters — the aforementioned book that caused the Great Flood of 1993 — and relieve over $16 billion in alluvion damage costs.

Mouth/Delta

The end of a river is its mouth, or delta. At a river'southward delta, the land flattens out and the water loses speed, spreading into a fan shape. Usually this happens when the river meets an ocean, lake, or wetland. Every bit the river slows and spreads out, it tin can no longer transport all of the sand and sediment it has picked up forth its journey from the headwaters. Because these materials and nutrients help build fertile farmland, deltas have been called "cradles" of homo civilization. Deltas are "cradles" for other animals likewise, providing breeding and nesting grounds for hundreds of species of fish and birds.

Wetlands

Wetlands are lands that are soaked with water from nearby lakes, rivers, oceans, or clandestine springs. Some wetlands stay soggy all year, while others dry out. Although wetlands are best known for providing habitat to a broad multifariousness of plants and animals, they also aid protect our communities past interim every bit natural sponges, storing and slowly releasing floodwaters. A single acre of wetland, saturated to a depth of one foot, will retain 330,000 gallons of water – enough to flood thirteen average-sized homes thigh-deep.  Wetlands also assistance provide clean water by naturally filtering out pollution.

Flow

"Flow" refers to the water running in a river or stream. There are two important aspects to a river's natural flow. Kickoff, there is the amount of h2o that flows in the river. Some rivers get enough water from their headwaters, tributaries, and rain to flow all year round. Others become from cold, raging rivers to minor, warm streams as the snowpack runs out, or fifty-fifty finish flowing completely. A river'due south natural ups and downs are called "pulses." Like a human beingness's pulse, a river's natural flow of h2o is life support for animals, plants, and fish, delivering what they need to survive at the right times. When nosotros divert water away from a river, we change the river's natural catamenia.

The 2d component of natural flow is how water moves through a river's aqueduct. In a natural, wild river, the h2o runs freely. But in more developed or degraded rivers, dams and other structures can slow or stop a river'south flow.  When a river's flow is blocked, migratory fish similar salmon can suffer, unable to motion up or downstream.