[no_wizard]

what if you just pooled the water until it cooled down naturally under shade before discharging back into the Danube?

[hansthehorse]

Turkey Point plant in SE Florida uses miles and miles of man made switchback canals to cool the discharge before it returns to the plant.

[freeone3000]

The water, coming from uphill, is already cooler than it would be if it sat still at the current altitude. Streams and springs average the temperature out over months, not simply a few hours.