Blackwater river

This article is unconnected to the various rivers named Blackwater: see Blackwater River (note capitalization)

Blackwater rivers are rivers with waters colored like clear tea to coffee. Most major blackwater rivers are in the Amazon River system and the American South.

Missing image
Amazon_blackwater.JPG
Amazon River tributary classified as blackwater
Missing image
Manaus-Amazon-NASA.jpg
Manaus, the largest city on the Amazon River, as seen from a NASA satellite image, surrounded by the muddy Amazon River and the blackwater Negro River.

A blackwater river is one with a deep, slow-moving channel that flows through forested swamps and wetlands. The term blackwater describes the appearance of the water of such rivers, which is a dark coffee color. This color results from the leaching of tannins from the decaying leaves of adjoining vegetation.

Blackwater rivers are also characterized by striking water clarity; so clear that visibility regularly exceeds 30 feet (9 meters). However, after rainstorms blackwater rivers can lose their typical clarity and color while sediment runs off from the surrounding forest. Within a few hours to a few days, the normal conditions return.

Chemically, blackwater rivers are very low in dissolved minerals and often have no measurable water hardness. The very acidic, almost sterile water, with a pH of 3.5-6, keeps parasite and bacterial populations to a minimum. For this reason, blackwater rivers are considered some of the cleanest natural waters in the world, most often compared to "slightly contaminated distilled water." The water chemistry of blackwater also inhibits the proliferation of insect larvae, so the forests around blackwater rivers tend to have less floor-dwelling mosquitoes. This chemistry also makes blackwater rivers unsuitable for public water supplies.

Contents

Blackwater rivers of the world:

Amazonia

American South

American North

See also

Resources

See also: Blackwater river, Acid, Albemarle Sound, Amazon River, Atlantic Ocean, Bacterium, Black River (South Carolina), Blackwater River, Cape Fear River, Coffee