the heat absorbed by the circulating cooling water in the condenser tubes must also be removed to maintain the ability of the water to cool as it circulates. this is done by pumping the warm water from the condenser through either natural draft, forced draft or induced draft cooling towers (as seen in the adjacent image) that reduce the temperature of the water by evaporation, by about 11 to 17 °c (20 to 30 °f)—expelling waste heat to the atmosphere. the circulation flow rate of the cooling water in a 500 mw unit is about 14.2 m/s (500 ft/s or 225,000 us gal/min) at full load.