Rivers (along with streams, reservoirs and wetlands), host less than 1% of the total volume of fresh water on Earth. Therefore, they are a key piece for people’s water supply and consumption. However, its quality and conservation is threatened by human activities. It is possible that ignorance has led us to this situation, because: what exactly do we know about them? Have you ever wondered what the course of a river is like or what is called the amount of water that a river carries? What types of rivers are there? How important are rivers?
What is a river
Rivers are defined as masses of surface fresh water that move or flow through physical channels, called channels , from higher elevations to lower elevations by gravity itself. In addition, it should also be noted that the route of the water of the rivers is called the course of the river . These fresh water currents mainly originate in high mountain areas due to the accumulation of rainwater, water from springs, melting and melting snow.
Although, as in theory, in our mind, we relate rivers to bodies of surface water, it is true that there are underground river systems , whose origin takes place in karst processes on the ground.
Finally, in relation to the characteristics of rivers , it is worth highlighting their capacity to modify and model the landscape through the processes of erosion, transport of materials and sedimentation (deposition).
Parts of rivers
Having clarified what a river is, we now answer the main question about what are the parts of a river , as well as what are the characteristics of the parts of a river. Along the longitudinal profile of a river, 3 parts or sections can be distinguished :
Upper course of the river
Close to the source of the river in the mountain areas with high slopes. In this course the river waters have a low flow and circulate at high speed, simulating a torrent, so there is a high capacity for erosion and sediment transport .
Middle course of the river
In this part of the basin, with less slope, the transport and accumulation of sediments predominate. In this section the river has a greater amount of flow and its waters are slowing down, this being less than in the previous section, the upper course.
Lower course of the river
In the vicinity of the mouth, the waters of the river circulate at low speed. Sedimentation predominates and, when the rivers flow, they can form estuaries, deltas or estuaries .
In addition, other elements of a river are: its source, its channel and the banks, among others.
According to their period of activity and, therefore, the dynamics and origin of the flow (which refers to the amount of transported water) rivers can be classified into:
- Perennial rivers: located in areas of abundant rainfall or with good groundwater supply (from groundwater ).
- Seasonal rivers: typical of high mountain areas, they are typical of the Mediterranean, where the seasons are very different and wet and dry periods predominate. That is why they have strong ups and downs in the flow.
- Transitory rivers: located in areas with a humid or desert climate, they present an irregular flow due to the scarce annual rainfall, which means that they can remain without water for long periods and also suffer violent floods caused by storm discharges and torrential rains.
- Allochthonous rivers: they cross arid areas, but their water comes from rainier and more humid areas. Examples: River Nile and River Okavango (both African).
Alluding to the “braiding method” created by Rust (1978), according to its geomorphology, taking into account the sinuosity and the number of internal bars or sandy deposits that they have (multiplicity), the following are distinguished:
- Straight rivers: with a single channel and channel, they are infrequent and unstable. They stand out for their low sinuosity and their high slopes, which favor the dragging and transporting processes of materials.
- Anastomosed rivers: with high sinuosity, they are subdivided into several channels, similarly to braided rivers, forming semi-permanent stable fluvial islands. They are usually located in areas of low slope, thus predominating sedimentation processes.
- Braided or braided rivers: they have branches or arms that join and separate their course, drawing a braid. They have surplus solid cargo (gravel, sand, and block) and are common in areas with extreme weather conditions.
- Meandriform rivers : they are stable rivers that curve into meanders , in whose banks erosive and sedimentary processes predominate. They present alluvial plains that favor flooding processes.
On the one hand, based on the distance between the source and the mouth of a river, the longest rivers in the world include:
- Yellow River
On the other hand, the largest rivers in the world are:
To finish, these are some of the rivers in Spain :
- There are 8 main rivers: Mino, Ebro, Duero, Tajo, Jucar, Guadiana, Segura and Guadalquivir.
- The longest rivers are: Ebro, Guadiana, Guadalquivir, Jucar and Genil.