With 3.9 million km 2 , the Amazon is the largest river basin in the world. It bathes almost half of the Brazilian territory. The main river in this basin, the Amazonas, is the most extensive and the largest volume of water in the entire globe.
We know that the Amazon River is not entirely Brazilian, as it rises in Peru, at 5,500 meters of altitude, in the heart of the Andes. In Peruvian territory, before entering our territory, this famous river is called Apurimac and Ucayali, into which the affluent Marahon flows.
When entering the Brazilian territory, in the State of Amazonas, the Ucayali river receives the name of Solimões and is so called until it receives the waters of the Negro river, next to the city of Manaus. After the confluence with the Negro River, it receives the name of Amazonas, and with that name it remains until its mouth, in the State of Pará, next to the island of Marajó.
In basins located in the Amazon , the most diffuse and most penetrable channels are traditionally used as waterways. The fact that the great Amazonas-Solimões artery has a vast network of tributaries and crosses the region in an east-west direction, linking the Brazilian Amazon to other countries – mainly Peru and Bolivia – greatly contributed to the dominance of these roads.
Among the numerous river ports in the Ama Basin zones, the main ones are:
- Belém, on the Amazon River, in the State of Pará;
- Manaus, on the Negro River, in the State of Amazonas;
- Santarém, on the Amazon River, in the State of Pará.
The Amazon Basin, on the other hand, has the lowest percentage of plants in operation and / or construction – 0.46% of the potential – quantity below regional needs. Due to the geographic dispersion characteristics of urban centers, the main nuclei of demand, the construction of a larger number of generating units is necessary. However, the dominant flat topography in the region, which leads to the flooding of huge areas for the construction of reservoirs, comes in opposition to the ideas of preserving the current vegetation cover in the Amazon.
The importance and richness of a river are incalculable. It supplies riverside populations with water, food such as aracus, pacus, peacock bass from the Amazon; it serves as a route of circulation and fertilizes the marginal region – lowland – with sediments rich in nutrients for agricultural practice. But are men aware of this importance and of the need to keep rivers clean and alive so that water resources are conserved?
In the Amazon, many rivers have been contaminated by mercury, a metal used by garimpeiros to facilitate the exploitation of gold. This concerns environmentalists and health professionals. as some local populations who drink the river water without treatment have already shown symptoms of cumulative contamination, which affects the central nervous system.
São Francisco River Basin
According to Proexchangerates.com, the São Francisco River Basin is the most important Brazilian river basin, as it is entirely within our territory. It extends to the states of Minas Gerais, Goiás, Bahia, Pernambuco, Alagoas and Sergipe, and also to the Federal District. Its area is 631,133 km 2 (more than 7% of the Brazilian territory).
The São Francisco River rises in the Serra da Canastra, in Minas Gerais and flows in a north-northeast direction, crossing the entire state of Bahia. It is the natural border between Bahia and Pernambuco, Bahia and Alagoas and Alagoas and Sergipe. It flows into the Atlantic, with a length of 3,161 km.
Being a typical plateau river, the São Francisco has dams and waterfalls that are well used in the production of electricity. The Paulo Afonso and Sobradinho plants in Bahia, Três Marias plants in Minas Gerais, Xingó plants on the Alagoas and Sergipe border, Itaparica plants in Pernambuco and Moxotó plants in Alagoas are its main hydroelectric plants .
Even characterizing the Bahian hinterland, the São Francisco Basin has a tropical regime, that is, it has an annual flood. This tropical regime is mainly due to the rains that occur in the southern part of the basin, in the State of Minas Gerais.
Despite being a plateau river, the São Francisco is navigated in a good part of its course. It is the stretch that extends from Pirapora (MG), until the urban binomial of Juazeiro (BA) -Petrolina (PE).
The “Velho Chico” bathes a large part of the State of Minas Gerais, which is experiencing a moment of exceptional industrial expansion. Along with all the benefits that the river provides with hydroelectric potential, navigation and irrigation there is an environmental risk.
Industry, mining and agriculture are the main emitters of toxic pollutants in the waters. Polluting substances include minerals; oil products, mercury, lead – discharged by mining industries and activities -; fertilizers, pesticides and herbicides – used by agriculture and dragged by the rains to the rivers.
There are already laws in Brazil that oblige companies to make environmental impact reports, presenting plans for the recovery of degraded areas.
As for sewage treatment, this is an issue that depends on public resources and political will. To get an idea of the size of the problem, just remember that in 1997 the IBGE calculated that in 27.5% of Brazilian homes there are only septic tanks or waste is thrown directly into ditches, rivers, lakes or into the sea.
Together with the Amazon Basin, the Tocantins-Araguaia system has been studied , which, according to the IBGE Foundation, is a separate river basin, with 803,250 km 2 .
The Tocantins River , with its tributaries, bathes most of the States of Goiás, Tocantins and small parts of the States of Pará, Maranhão, Mato Grosso, Mato Grosso do Sul and the Federal District. It flows into the right bank of the Amazon River, next to the island of Marajó.
The Araguaia River , which separates the State of Goiás from the States of Mato Grosso and Pará, has in its course the famous Bananal Island (the largest river island in the world) and is the main tributary of the Tocantins River.
The Tocantins River is navigable for about 1,900 km, from the city of Belém (Pará) to Peixe (Goiás), on the Goiás plateau. However, due to the dangerous obstacles caused by rapids and sandbanks during droughts, it can only be considered usable throughout the year from Miracema do Norte (Tocantins) downstream.
The Araguaia River is navigable for about 1,162 km between São João do Araguaia and Beleza, without any major urban center on its route.
Despite being, for most of its course, a lowland river, presenting no difficulty in navigation, it is not fully used.
The Tocantins-Araguaia basin has 67.29% of its inventoried energy potential, with only 22.64% in operation or under construction. Its main hydroelectric plant is Tucuruí, in Pará.