>>7777467It apparently goes back to the 1950's when the local Nickel & Copper mine was in operation and the waste products were being stored in special areas called impoundments.
Over time the waste minerals (mostly iron) stored in the impoundments oxidised through contact with water and air, hence why the river in the picture is bright red/orange in colour, because amongst other things it's full of iron oxide (i.e. rust).
That photo is part of a series of photos shot in the area in 1996. A search for 'Sudbury Nickel Tailings' should find more of the photos, and more details.
