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Araguaya River

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Along its course, the river forms the border between the states of Goiás, Mato Grosso, Tocantins and Pará. Roughly in the middle of its course the Araguaia splits into two forks (with the western one retaining the name Araguaia and the eastern one being called the Javaés River). These later reunite, forming the Ilha do Bananal, the world's largest river island.[3] The vein of the Javaés forms a broad inland where it pours back into the main Araguaia, a 100,000 hectare expanse of igapós or flooded forest, blackwater river channels, and oxbow lakes called Cantão, protected by the Cantão State Park. It is one of the biologically richest areas of the eastern Amazon, with over 700 species of birds, nearly 300 species of fish, large populations of species such as the giant otter, the black caiman, the pirarucú, one of the world's largest freshwater fish, and the Araguaian river dolphin (or Araguaian boto), all occurring within a large area.

Several parts of the river's course are protected by national parks and other reserves like the Emas National Park and the Araguaia National Park. The Araguaia has "beaches" - bright sandy banks that seam the stream from May to October.

Deforestation and expansion of cattle ranching and agriculture in the Araguaia basin has been extreme during the last four decades.[7][non-primary source needed] As a consequence, strong linear erosion has produced thousand of gullies just in the upper Araguaia basin, and the river mainstem suffered strong sedimentation and fluvial metamorphism (changes in its channel pattern).[8][non-primary source needed]

The Tocantins-Araguaia Basin is one of the largest river systems in South America, located entirely within Brazilian territory. In the last decades, capital-concentrating activities such as agribusiness, mining, and hydropower promoted extensive changes in land cover, hydrology, and environmental conditions. These changes are jeopardizing the basin's biodiversity and ecosystem services. Threats are escalating as poor environmental policies continue to be formulated, such as environmentally unsustainable hydropower plants, large-scale agriculture for commodity production, and aquaculture with non-native fish. If the current model persists, it will deepen the environmental crisis in the basin, compromising broad conservation goals and social development in the long term. Better policies will require thought and planning to minimize growing threats and ensure the basin's sustainability for future generations.

The Araguaia River floodplain is a large wetland in the tropical savanna belt (cerrado) in the southern Amazon basin. Studies using multitemporal satellite Landsat 5 TM images with a spatial resolution of 30 m indicate a surface area at maximum flood level of 88,119 km2. During the low-water period, only 3.3 % of the area is covered by water. Flooding is the result of the annual rise in the water level of the Araguaia River and of local rainfall and insufficient drainage during the rainy season. Sedimentology studies have distinguished between an active recent and sub-recent floodplain, which covers 20 % of the area, and a paleo-floodplain probably several hundreds of thousand years in age. Paleo-floodplain sediments are strongly weathered and marked by the clay mineral association of kaolinite, gibbsite, goethite, and Al-chlorite, predominantly formed from feldspars and micas. The active paleo-floodplain participates in the hydrological cycle but does not receive recent sediments from the river. Higher-lying, not flooded areas (inactive paleo-floodplain) are probably the remnants of paleo-levees, now in an advanced stage of erosion. A hypothesis to explain the genesis of the floodplain is proposed herein.

This study examined the hydrological behavior of the Araguaia River through reference flow, analyzing the capacity of granting the river segments in three different fluviometric stations. The study exposed the comparison of monthly and annual referenc


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