Nhamundá River or Jamundá River ( Yamundá River in Spanish) is a river in northern Brazil , which marks part of the northeastern boundary between states of Amazonas and Pará . The 300 km long Nhamundá River originates in the plateau Serra do Jatapu near the division of the Brazilian States of Roraima , Amazonas and Pará, and from there it flows in a southeastern direction, forming the natural division between Amazonas and Pará. It then crosses the Nhamundá-Mapuera Reserve (EG033) before joining the Trombetas River near the city of Oriximiná . The river, which flows through the Lago Nhamundá , is the last major right-hand affluent of the Trombetas River before the Trombetas joins the Amazon River . The mouth is located about 480 km east (downstream on the Amazon) of Manaus .
8-785: A blackwater river is a river with a deep, slow-moving channel flowing through forested swamps or wetlands. Blackwater River may also refer to: Blackwater river A blackwater river is a type of river with a slow-moving channel flowing through forested swamps or wetlands . Most major blackwater rivers are in the Amazon Basin and the Southern United States . The term is used in fluvial studies, geology , geography , ecology , and biology . Not all dark rivers are blackwater in that technical sense. Some rivers in temperate regions, which drain or flow through areas of dark black loam , are simply black due to
16-570: A low conductivity , similar to that of rainwater. Black and white waters differ in their planktonic fauna and flora. Tables 2 and 3 compare the number of planktonic animals caught in black and white water localities only a few meters apart. The black water was not as extreme an example as the Rio Negro system. However, it can be seen that the black water held greater numbers of rotifers but fewer crustaceans and mites . These crustaceans are important foods for larval fish . The zones where
24-855: Is somewhat acidic (typical pH ~6.5) and very clear with a greenish color. The main Amazonian clearwater rivers have their source in the Brazilian Plateau (such as Tapajós , Tocantins , Xingu and some right tributaries of the Madeira ), but some originate in the Guiana Shield (such as Nhamundá , Paru , and Araguari ). Other rivers in Australia may experience infrequent 'blackwater events' associated with flood waters connecting to forested floodplains and these events may be associated with hypoxic waters [low oxygen]. Examples include
32-575: The Murray River , Edward River , Wakool River and Murrumbidgee River . Nhamund%C3%A1 River The three towns on the river's lower reaches ( Terra Santa , Nhamundá , and Faro ) are accessible only by boat. This article related to a river in the Brazilian state of Amazonas is a stub . You can help Misplaced Pages by expanding it . This article related to a river in Pará , Brazil
40-400: The color of the soil; these rivers are black mud rivers . There are also black mud estuaries . Blackwater rivers are lower in nutrients than whitewater rivers and have ionic concentrations higher than rainwater. The unique conditions lead to flora and fauna that differ from both whitewater and clearwater rivers . The classification of Amazonian rivers into black, clear, and whitewater
48-418: The more neutral white waters. The major difference is the concentrations of sodium , magnesium , calcium , and potassium ; these are very low in black waters. This has ecological implications. Some animals need more calcium than is available in blackwaters, so for example, snails , which need much calcium to build shells, are not abundant in blackwaters. The lack of dissolved ions in black waters results in
56-473: The two waters mix are attractive to ostracods and young fish. These mixing zones tend to have many animals. The abundance is shown in Table 3, which compares animals in 10 litres (2.2 imp gal; 2.6 US gal) of water. Blackwater rivers resemble clearwater rivers in having a low conductivity and relatively low levels of dissolved solids , but clearwater rivers have water that often only
64-620: Was first proposed by Alfred Russel Wallace in 1853 based on water colour, but the types were more clearly defined by chemistry and physics by Harald Sioli [ de ] from the 1950s to the 1980s. Although many Amazonian rivers fall clearly into one of these categories, others show a mix of characteristics and may vary depending on season and flood levels. Black and white waters differ significantly in their ionic composition, as shown in Table 1 . Black waters are more acidic , resulting in an aluminum concentration greater than that of
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