Every river runs a course from its source to its mouth or mouth. In this way you can catch more water from other sources (dispersing centers) and increase. This area of the route made by several watercourses, coming from different regions, but converging to the same point, is what we call the river basin .
The hydrographic basin, therefore, is the set formed by the main river, its tributaries and the lands bathed by them. It is considered tributary or tributary any water course that flows into another river or a lake, contributing to increase its volume of water.
Normally the spring of the rivers that form the watersheds is in the highest areas and corresponds to the outcropping of the groundwater table. Therefore, the occurrence of rainfall is fundamental to feed these aquifers, thus forming the springs or water eyes.
Under the soil layers, permeable material is a layer of rock which is a material impermeable. It is precisely in this contact that the formation of groundwater sheets occurs. When the accumulation of water reaches the surface the headwaters of the rivers appear.
In Brazil, this is the main source of hydrographic basins. However, in the case of the Amazon basin , there are rivers that receive water in their sources from the melting of snow in the Andes mountain range; the Amazon River is a good example.
Elements of a river basin
The highest areas bordering the basins are the water dividers , that is, the elevations that separate the waters flowing to different river basins, and the slopes where they flow are the slopes.
When a river in a river basin runs through a very rugged relief area and for this reason has many waterfalls, we say that it is a plateau river. The plateau rivers have as their fundamental quality their high hydroelectric potential.
Likewise, when crossing an area with few gradients, usually forming meanders , it is called a plain river. These rivers have as fundamental characteristic their navigability.
Another important element of a river basin is the flow of its waters. It is conditioned by natural factors, such as snowmelt and rainfall. The river that has a strong influence of the melting of snow in the volume of its waters has a regime of the nival type and, when it is the rains that exert such influence, the regime is pluvial.
There may be rivers, such as the Amazon, in South America, where the regime is mixed, that is, the pluvial-nival type, because the Amazon is born in the Andes, receives water from the melting snow near its high course and then travels to the equatorial region, where abundant rains occur and contribute to substantially increase its water volume.
Types of basins
Basically, watersheds can take two distinct paths: one that causes rivers to flow into the ocean, that is, they flow out of the country’s territory and that directs the course to the interior of the country.
The former are called exorreic watersheds , and the latter, called endorheic basins .