The waters of the Rio Negro, the largest left tributary of the Amazon River, live up to their name and, therefore, are certainly murky
The Rio Negro, 1,700 kilometres in length, is the longest blackwater river in the world and the second largest in terms of volume, losing only to the Amazon River itself. But what are these black waters exactly?
The Rio Negro’s water has a dark colouration, perhaps similar to that of brewed tea, due to the decomposition of organic sediments along the river. That is, leaves and other vegetation decompose and release certain tannins that give the water a notably darker hue.
One of the main tourist attractions in the region is where the dark waters of the Rio Negro meet with the muddier waters of the Solimões River. They flow, side by side, in completely separate channels for about six miles. This phenomenon is only possible due to the differences in temperature and density of the two rivers.