If you look in the Spain-gallery of my website you'll notice a fair number of yellow-reddish photos. These are taken near Rio Tinto, which I have visited on several occasions. The Rio Tinto – in English 'Red River' – is situated in south-west Spain and has its origin in the mining area carrying the same name.
Since Roman ages and probably long before, the area was extensively used for the production of precious metals. Erosion of the ores and the large-scale application of chemicals for the extraction of the metals, has resulted in large quantities of acids and (mostly iron) salts dissolved in the water. This gives the river its typically red colour. The extension of the pollution varies significantly. In dry spells the river is locally dark red. During wet periods and near tributaries carrying clean water, it can be much clearer while sometimes algae are growing in it. Overall, this results in a wide colour palette. From a distance for sure it all looks rather filthy; detailed views nevertheless can be beautiful and fascinating.
Meanwhile the mines have been closed for years and part of the area is even declared a Spanish National Park. The peculiar colours, however, are expected to remain for many years to come, the more so as the pollution probably also has a natural component.

I like working with details. The particular photo shown here was taken last year in the early evening in the beginning of summer. Heavy thunderstorms were hitting the area for a number of days, so there was a lot of water coming from the hills and much dilution. While taking pictures with all this water around you, I found it hard to imagine how much different the end result was as compared to the experience at the time. An exposure time of a few seconds resulted in a very nice, serene atmosphere.

Hasselblad 150mm f/32 + polar, Velvia 50