Blackwater river

[3][4] 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.

The major difference is the concentrations of sodium, magnesium, calcium, and potassium; these are very low in black waters.

The lack of dissolved ions in black waters results in a low conductivity, similar to that of rainwater.

Tables 2 and 3 compare the number of planktonic animals caught in black and white water localities only a few meters apart.

[8] 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).

A swamp-fed stream in northern Florida , showing tannin-stained undisturbed blackwater
The Lumber River as seen from the boat launch at Princess Ann near Orrum, North Carolina
Chocolate-colored Tahquamenon Falls