- water
- cooling
- data-center
Closed-loop cooling recirculates its cooling water rather than returning it to the source. The system loses water two ways — evaporation from the cooling tower, and periodic blowdown to purge concentrated minerals — and makes up the difference with fresh withdrawal. The result inverts the once-through profile: a modest withdrawal but a high consumptive fraction.
For a hyperscale data center this is the design that matters to the river, because most of what it withdraws is lost to evaporation and never returns downstream — the consumptive cooling that is subtracted from live flow in the dilution and assimilative capacity screen. It also concentrates whatever is in the make-up water, so blowdown itself can become a permitted discharge. A recirculating design cuts the withdrawal an once-through cooling plant would need while raising the share that leaves the watershed for good.