Dark red pools of meltwater from acid rock drainage on Pastoruri peak in the Cordillera Blanca, a Peruvian mountain range containing the world’s largest concentration of tropical glaciers.

Throughout the Arkansas River Valley sagging mine shafts offer a glimpse into a bygone era of mining, but these sites are far ...

Percolation - The downward movement of water from the soil into the rock beneath. Drainage basin - the area of land drained by a river. Channel - the bed and banks that form the route of the river.