Rio Tinto's Red Water

May 31, 2015


Photographer: Margaret Watson
Summary Authors: Margaret Watson; Jim Foster

The Rio Tinto (Red River) in southwestern Spain has its source in the Sierra Morena Mountains. From here it flows toward the southwest and empties into the Gulf of Cadiz. Mining for copper, gold and silver, as well as other minerals, has been ongoing in this area for approximately 5,000 years. Eventually, the mines were abandoned but then rediscovered some 500 years ago. 

The Rio Tinto is highly acidic, but the red coloration of the water shown above is primarily due to dissolved iron. Aerobic bacteria living in the river water and feeding on iron and sulfate minerals on the river bottom contribute to the Rio Tinto's extreme acidity. Photos taken on April 28, 2011.

Photo details: Nikon D7000 camera;- Lens 18-105mm lens; F5.6; 1/200 second exposure; ISO 100.