Another scan; this photo was taken north of Lake Callabonna, South Australia, in 1984. It's not a natural lake but a clay pan between sand dunes fed by a never ending flowing bore. At the time I estimated it was easy big enough for three ski boats to use at the same time, as a size comparison. It was one of those South Australian government bores that flowed unrestricted for many, many years before they finally started to close them down. I don't think there's any left flowing like that now.
The bore was sunk on the side of a sand dune and the flow had cut a deep ravine in the dune that was deep enough to die from the fall. If that didn't kill you, the boiling water would. You had to go 500 metres downstream before the water was cool enough to have a hot spa bath; I'd estimate it flowed about a kilometre all up from the bore to the lake. Judging by irrigation bores I've seen, I guessed the flow at between 20,000 to 30,000 gallons per hour, flowing year after year. Evaporation over the large lake area would have accounted for a fair portion of the water loss.