He negro river is the largest blackwater river in the world. “blackwater” refers to the fact that it is a deep river that flows slowly through forested swamps and wetlands, with dark-colored waters as a result of tannins that are leached out of decaying vegetation. what country does this blackwater river flow through?

colombia
venezuela
peru
brazil
ecuador

Brazil is the country where the black water river flows through.

Explanation:

The Negro River rises in the southern highlands of Brazil   and it is east of Bagé .

The Negro river flows into Uruguay in the south west direction, and it is dammed near Paso de los Toros in order to create the Rincon Del Bonete Reservoir and this is also named as the Gabriel Terra Reservoir or the Rio Negro Reservoir. This river is one among the largest artificial lakes in South America  

not completely sure but i think it’s many moons, smaller in size and a ring system.