Tocantins River in the context of "Pará River"

The Amazon Delta (Portuguese: delta do Amazonas) is a vast river delta formed by the Amazon River and the Tocantins River (through the Pará River distributary channel) in northern South America. It is located in the Brazilian states of Amapá and Pará and encompasses the Marajó Archipelago, with Marajó Island as its largest island. The main cities located in the vicinity are Belém and Macapá, each with its respective metropolitan area.

The Amazon Delta has a tropical climate with high humidity and high temperatures. It has a wet season with frequent flooding and a dry season where the delta dries out. These seasons shape the environment of the Amazon Delta and the life in it, such as the water buffalo for which Marajó Island is well known, three-toed sloth, capybara, giant anteater, giant otter, jaguar and pink river dolphins.

Tocantins (Brazilian Portuguese: [tokɐ̃ˈtʃĩs] ) is one of the 26 states of Brazil. It is the newest state, formed in 1988 and encompassing what had formerly been the northern two-fifths of the state of Goiás. Tocantins covers 277,620.91 square kilometres (107,190.03 sq mi) and had an estimated population of 1,496,880 in 2014. Construction of its capital, Palmas, began in 1989; most of the other cities in the state date to the Portuguese colonial period. With the exception of Araguaína, there are few other cities with a significant population in the state. The government has invested in a new capital, a major hydropower dam, railroads and related infrastructure to develop this primarily agricultural area. The state has 0.75% of the Brazilian population and is responsible for 0.5% of the Brazilian GDP.

Tocantins has attracted hundreds of thousands of new residents, primarily to Palmas. It is building on its hydropower resources. The Araguaia and Tocantins rivers drain the largest watershed that lies entirely inside Brazilian territory. The Rio Tocantins has been dammed for hydropower, creating a large reservoir that has become a center of recreation. Because it is in the central zone of the country, Tocantins has characteristics of the Amazon Basin, and also semi-open pastures, known as cerrado. The Bananal Island (Ilha do Bananal), in the southwest of the State, is the second largest fluvial island in the world. Tocantins is also home to the Araguaia National Park, the Carajás Indian reservations, and Jalapão State Park, which is about 250 kilometres (160 mi) from Palmas. There, the rivers create oases in the dry landscape, attracting many ecotourists to the region.

Marajó Bay, the Marajoara Gulf or the Amazon Gulf, is a recessed body of water of the Brazilian coast located in the state of Pará. It is roughly 4,500 km (1,700 sq mi) in size, and is a receptacle for the waters of the Pará River distributary channel, the waters of the Tocantins basin and the waters of the Guajará Bay, serving as the eastern aquatic border of both the Marajó Island and the Marajó Archipelago. Marajó Bay is an estuary consisting of both salt and fresh water, resulting in the classification of an estuarine system. Marajó Bay also receives sediments from the Amazon River through the Breves Channel as well as the Pará River, causing the water to be turbid.

The Pará River and a small fraction of the Tocantins River are the main providers of water for Marajó Bay. The river is vital to the surrounding areas and makes different areas and ports very accessible for locals. The river also eventually clashes with salt water from the Atlantic Ocean in the Marajó Bay. A circulation process of salinity, temperature, and tidal range in the two different water types occurs in the bay as they meet. Salt water concentrations are also impacted by low water periods of the Amazon River.