Rivers

We explain what rivers are and what their sectors and dynamics are. Also, its general characteristics, its flora, its fauna and more.

What is a river?

The rivers are streams of fresh water that flow from higher areas of a region to lower areas. As the water descends, rivers take on different shapes and characteristics: sometimes they are wider and other times narrower; At times the water flows faster and at times slower; In some sections they have a greater slope and in others the slope is less.

Thus, The rivers flow towards the lowest areas until they reach sea levelor until it flows into the union with another river of greater flow, a lake or a lagoon.

Rivers are supplied by two sources of water: rain and snowmelt.. In places where it rains a lot during a time of year, rivers increase their flow and transport more water. For their part, rivers that are close to mountainous areas see their flow increase in the summer months, when high temperatures melt the ice on the mountain tops.

Parts of rivers

Rivers can be divided, for study, into three parts:

• Higher course. It is the part where the river originates, generally at altitude, in mountain ranges or mountains. In this course, the relief is usually very steep, so the water circulates at high speed and has a high erosion power.
• medium course. It is the part where the slope and speed of the water decrease, and the course of the river tends to widen.
• Lower course. It is the part closest to the mouth. In this course, the relief usually has very little slope, so the water circulates more slowly. In addition, rivers sometimes become meandering and form sharp curves, called meanders.

The flow of the rivers

Flow is the amount of water that circulates through a river and is measured in cubic meters per second (m³/s). This flow varies according to the river's fluvial regime, which can be pluvial, snowy or mixed.

• The pluvial rivers They increase their flow when rainfall increases in the place where they circulate.
• The snowy rivers They increase their flow in the hot months, when the ice found on the tops of the mountains where they are born melts.
• The mixed regime rivers They increase their flow due to a combination of rain and snowmelt.

Flora and fauna of the rivers

The banks of the rivers are characterized by presenting a varied range of flora adapted to humid conditions. Among the most common plant species are poplars, willows and alders.whose roots also contribute to the stabilization of the soil and prevent erosion.

It is also the presence of floating flora, such as water lilies and water hyacinths, is common. These plants have adaptations that give them buoyancy and allow them to develop in that aquatic environment.

As for fauna, the rivers are home to a diversity of species adapted to aquatic life. There are river fish, such as catfish and trout; aquatic invertebrates, such as crayfish; aquatic insects, and also large animals, such as manatees, crocodiles and hippos. Water birds, such as herons, also make up these ecosystems and find an abundant source of food in rivers.

The glaciers

A glacier is a mass of ice that originates on the earth's surface due to the accumulation and compaction of snow. Since they are almost always found in mountainous areas, the force of gravity slowly moves them downwards. For this reason, they are considered “rivers of ice”, although the water does not flow in a liquid state, as in most cases.

There are thousands of glaciers in the coldest areas of the planet and in the highest sectors of the mountain ranges. From the heights, glaciers descend at a speed of only two or three centimeters per day. Like traditional rivers, they also suffer variations due to different temperatures and seasons of the year: in winter, glaciers increase in size due to freezing, while in the hot months their volume decreases as a result of melting.

River pollution

River pollution is a very serious environmental problem worldwide. Especially in those rivers that cross large urban areas, the contamination of their waters is a problem that is very difficult for government authorities to address and solve. Furthermore, in these spaces, the consumption of unsafe water and exposure to contaminants causes serious illnesses in the population.

The main sources of river pollution are:

• Industrial discharges. The release of industrial chemical waste and toxic products poses a threat to water quality, aquatic life and human health.
• agricultural waste. Chemical products used in agriculture, such as herbicides or pesticides, often end up in rivers and contaminate their waters.
• Wastewater and sewage. Large cities use rivers to discharge household wastewater and sewage. These wastewaters, when untreated, deposit highly polluting chemical waste and pathogens.
• Plastic waste. The plastics and microplastics that are thrown into river waters take thousands of years to degrade and affect aquatic life.

The longest rivers in the world

Although it is sometimes difficult to establish the extent of rivers exactly, the longest rivers in the world are considered to be:

• Amazon River, with 7062 kilometers.
• Nile River, with 6853 kilometers.
• Yangtze River, with 6300 kilometers.
• Mississippi River with 6275 kilometers.
• Yenisei River, with 5539 kilometers.
• Yellow River, with 5464 kilometers.
• Obi River, with 5410 kilometers.
• Paraná River, with 4880 kilometers.
• Mekong River, with 4880 kilometers.
• Congo River, with 4700 kilometers.

Rivers in the development of human civilization

Rivers have played an essential role in the evolution of human civilizations. Its presence has been decisive in the social, economic and cultural development of various societies throughout history.

The Nile River has been the epicenter of Egyptian civilization for millennia.. It provided fertility to the surrounding lands through seasonal flooding, and allowed the practice of agriculture and the establishment of agricultural communities.

In the context of ancient Mesopotamia, the Tigris and Euphrates rivers were the pillars of the Sumerian, Akkadian and Babylonian civilizations. These rivers not only provided essential resources for the survival of these cultures, but also served as trade routes that connected these ancient societies to the rest of the known world.

In addition, The Ganges River has been a source of spiritual inspiration for India for millennia. Considered sacred by millions of Hindus, the Ganges is a pilgrimage destination and multiple religious rituals are performed in its waters.

References

• Anta Sánchez, A. (2019). Pollution of lakes and rivers: causes, consequences and how to avoid it. EcologyGreen. https://www.ecologiaverde.com/
• Tarbuck, E. and Lutgens, F. (2005). Earth Sciences. An introduction to physical geology. Pearson Education.
• Valdivieso, A. (sf). Fluvial regime of a river. iWater. https://www.iagua.es/