River

Sediment or alluvium carried by rivers shapes the landscape around it, forming deltas and islands where the flow slows down.

Humans have engineered rivers to prevent flooding, irrigate crops, perform work with water wheels, and produce hydroelectricity from dams.

People associate rivers with life and fertility and have strong religious, political, social, and mythological attachments to them.

The construction of dams, canals, levees, and other engineered structures has eliminated habitats, has caused the extinction of some species, and lowered the amount of alluvium flowing through rivers.

Regulation of pollution, dam removal, and sewage treatment have helped to improve water quality and restore river habitats.

[2] The study of the movement of water as it occurs on Earth is called hydrology, and their effect on the landscape is covered by geomorphology.

[3] In summer months, higher temperatures melt snow and ice, causing additional water to flow into rivers.

[7] The sediment yield of a river is the quantity of sand per unit area within a watershed that is removed over a period of time.

[12] The alluvium carried by rivers, laden with minerals, is deposited into the floodplain when the banks spill over, providing new nutrients to the soil, allowing them to support human activity like farming as well as a host of plant and animal life.

[14] These rivers can appear in a variety of climates, and still provide a habitat for aquatic life and perform other ecological functions.

A shady area with deciduous trees might experience frequent deposits of organic matter in the form of leaves.

[19] River ecosystems have also been categorized based on the variety of aquatic life they can sustain, also known as the fish zonation concept.

In this case, it is known as the species-discharge relationship, referring specifically to the discharge of a river, the amount of water passing through it at a particular time.

They can be thought of as dams constructed on the sides of rivers, meant to hold back water from flooding the surrounding area during periods of high rainfall.

[19] The freshwater, fertile soil, and transportation provided by rivers helped create the conditions for complex societies to emerge.

[26] Growing food at scale allowed people to specialize in other roles, form hierarchies, and organize themselves in new ways, leading to the birth of civilization.

[26] Drought years harmed crop yields, and leaders of society were incentivized to ensure regular water and food availability to remain in power.

[19] As fish and water could be brought from elsewhere, and goods and people could be transported via railways, pre-industrial river uses diminished in favor of more complex uses.

For example, swimming was banned in the Seine for over 100 years due to concerns about pollution and the spread of E. coli, until cleanup efforts to allow its use in the 2024 Summer Olympics.

[28] Another example is the restoration of the Isar in Munich from being a fully canalized channel with hard embankments to being wider with naturally sloped banks and vegetation.

[19] Ancient Greeks believed that the souls of those who perished had to be borne across the River Styx on a boat by Charon in exchange for money.

[19] Souls that were judged to be good were admitted to Elysium and permitted to drink water from the River Lethe to forget their previous life.

In Yoruba religion, Yemọja rules over the Ogun River in modern-day Nigeria and is responsible for creating all children and fish.

[34] Rivers that flow freely from headwaters to the sea have better water quality, and also retain their ability to transport nutrient-rich alluvium and other organic material downstream, keeping the ecosystem healthy.

[34] The creation of a lake changes the habitat of that portion of water, and blocks the transportation of sediment, as well as preventing the natural meandering of the river.

[35] Fertilizer from farms can lead to a proliferation of algae on the surface of rivers and oceans, which prevents oxygen and light from dissolving into water, making it impossible for underwater life to survive in these so-called dead zones.

This has resulted in a loss of animal and plant life in urban rivers, as well as the spread of waterborne diseases such as cholera.

[19] In modern times, sewage treatment and controls on pollution from factories have improved the water quality of urban rivers.

[33] This is in part because of a projected loss of snowpack in mountains, meaning that melting snow can't replenish rivers during warm summer months, leading to lower water levels.

Not only do these formations suggest that rivers once existed, but that they flowed for extensive time periods, and were part of a water cycle that involved precipitation.

A boat floats on the Mekong , in Laos
South America's Amazon River (dark blue) and the rivers which flow into it (medium blue). The darker green marks the Amazon's drainage basin or watershed
Flamingos in the delta of the Po river , Italy
The major drainage basins in North America
The end of a glacier, which looks like a wall of ice. Blue water filled with snow and ice is at the bottom of the cliff.
Melting toe of the Perito Moreno Glacier in Los Glaciares National Park , Argentina
The Grand Canyon was carved by the Colorado River .
A photo showing a wide river with a variety of low wetland vegetation on the sides.
The Nile in Egypt is known for its fertile floodplains, which flood annually.
A river of blue water flowing through a brown rock cave with sun peeking through.
The Blue Water Cave in Quezon , Philippines features an underground river.
A satellite photo of a large river delta with many branching paths.
The Lena river delta in Russia is formed from the river's sediment.
A diagram of a possible river with the Strahler number of each tributary labeled.
A few leafy trees around a small stream
The headwaters of the River Wey in England provide organic matter for organisms to process.
A small channel of water in the late fall or winter, surrounded by brown marsh-like vegetation
This marsh is a floodplain of the Narew in Poland .
A road over a raised embankment of earth, a marsh on the left side, and some small farms on the other.
This levee protects the city of Honghu in the Hubei province of China from flooding.
A grey dam in the distance spilling water from its center. Mountains are in the background.
The Na Hang Dam in Vietnam provides hydroelectric power.
The Sumerian civilization was made possible by the floodplains of the Tigris and Euphrates rivers.
A drawing of a man raising water from a river with a bowl mounted on the end of a large rod with a counterweight on the other end
The counterweight system of the shadoof is an early example of the engineering of river water.
A red brick building built over a waterfall. The waterfall is a concrete dam structure.
The Cochecho mill in Dover, New Hampshire , United States was a textile mill powered by the pictured hydroelectric dam.
A small boat pushes a large flat barge down a wide river in the fall
The barge is one of the primary means of shipping goods on the Mississippi and other rivers.
The Tiber river in Rome near the Ponte Sant'Angelo , Italy
A small flat section of canal in the French countryside
The Canal du Midi was one of the first large canal projects in the world.
A medium-sized boat leaving a wake as it travels through murky waters
This U.S. Customs and Border Protection boat is attempting to prevent crossings of the Rio Grande river from Mexico into the U.S.
A slow moving river at sunset reflecting the sky
The Ogun River in Nigeria is sacred to the Yoruba.
A castle built into the side of a river with a series of steps leading down into it.
The ghats along the Ganges river are the steps that allow people to bathe and release the ashes of the dead. [ 31 ]
A satellite image of a river running dry.
The Colorado River now runs dry in the deserts of Mexico, rather than running to the sea, due to diversion of water for agricultural uses. [ 32 ]
Snow-capped mountains above a lake
Retreating snow in the Rocky Mountains is expected to reduce the level of waters in the Western United States .
An orange moonscape, showing the rusty Mars soil. Impressions in the sand show where rivers once flowed, in a fractal-like form.
A dried out network of river valleys on Mars