Hydrographic basin is the drainage area or region of a main river and its tributaries. It is the portion of space in which rain, mountain, underground or other river water flows towards a certain watercourse, supplying it.
It is important, therefore, to be aware that when we are walking on the streets or in a forest, for example, we are walking necessarily over the area of a hydrographic basin, as the waters that eventually drain from these locations tend to direct to a river.
Representative scheme of the area of a hydrographic basin
What separates one watershed from another are the water dividers. They are like a kind of boundary where, on the one hand, the water flows towards a river and, on the other, the water flows towards another river.
Due to the force of gravity, water always runs from the highest point on the surface towards points with lower altitudes. Thus, we can say that the highest locations are the watersheds and the lower points usually shelter the river beds.
Mind Map: What is a watershed?
*To download the mind map in PDF, Click here!
Watersheds can be classified according to their magnitude. This is because every river has its own basin, but some of them flow into other rivers, forming a larger hydrographic basin, that is, the larger basins encompass the areas of other basins minors. See the diagram below, in it we have the situation of a hypothetical hydrographic basin, formed by a main river and its tributaries.
Graphic representation of a hypothetical hydrographic network
We can notice, in the diagram above, that the basin number three – of the third magnitude – is surrounded by the basin of the second magnitude, which, in turn, is part of the larger basin of the first magnitude. Thus, we have the formation of a hydrographic network.
As the hydrographic basin usually collects all surface or underground water from its waters towards the bed of a watercourse, it is not difficult to imagine that the pollution rate of your area will inevitably affect the river in question. Therefore, we can see that the good use and conservation of our water resources are directly related to the conservation of soil and underground areas.
* Mind Map by Rafaela Sousa
Geography teacher
By Me. Rodolfo Alves Pena
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/geografia/o-que-e-bacia-hidrografica.htm