Rivers that have deep brown or black-coloured water are called Blackwater Rivers. Here again, the name could be pretty much misleading. If you thought that these waters are polluted and undrinkable, you are wrong!
In fact, rainforest Blackwater Rivers are considered the clearest and cleanest of all natural river bodies. They are so clear that you can actually see the bottom of the river bed! Then why are they black?
Certain living plants produce certain toxins in their body to protect themselves from leaf-eating insects and other predators. When these plants decay or leaves fall, the toxin-rich plant debris is carried along with the river current. This decaying plant matter deposited beneath the water gives it a dirty black appearance.
Blackwaters are relatively softer in terms of water hardness but are more acidic than white-water rivers. This explains why the two tributaries of the Amazon River, the blackwaters of the Rio Negro River and the white waters of the Solimones River, do not mix when the two water channels combine. They flow next to each other, dark on one side and light on the other!
This high acidity level also makes it impossible for microbes and parasites to survive. Hence, the water is sterile and as good as distilled water. Hence, only a few plant and tree species thrive in these unfavourable forest conditions and this considerably lowers insect varieties and animal species too.
Picture Credit : Google
