Near Gladstone in Queensland, Australia is a gigantic, bright-orange lake known as Red Mud Dam. Although the explanations I found were a little confusing, it seems that the colouring is due to residue formed through the process of extracting aluminium from bauxite. I think. You can see that the colour only seems to be affecting about 2 thirds of the lake, as I believe the mud is processed to remove the residue. However, I’m sure someone out there will correct me, even if I’m right 😉 Thanks to Stuart Moffatt and Stephen Hope.