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