Copahue erupted in 2000 in Chile impacting both Chile and Argentina.
Copahue Volcano is a large stratovolcano situated on the border between Argentina and Chile. During eruptions in July 2000, 30-50 milimeters of ash was deposited in and around Lake Caviahue. Water authorities in the area reported changes in water color from normal deep blue to greyish green. In the days/weeks following the eruption the pH of the lake dropped to 2.1. Ashfall reported 60 kilometers from the volcano caused increased turbidity in streams and changes in pH from a typical pH of 7 to 2.5. Preliminary investigations by Argentina's Provincial Water Division revealed increased iron, fluorine and sulphate levels in water supplies. Ashfall related damage resulted in power outages to water treatment plants and cut off potable water supplies (see Global Volcanism Program, Smithsonian Institution).