Water use is one of the first objections raised when an AI data centre is announced, although the actual demand varies sharply by cooling design and location. Some facilities use substantial water for cooling, some use comparatively little, and the details of the cooling system and local weather make a major difference. A company saying its servers are liquid-cooled doesn't settle the question. Liquid can circulate in a closed loop inside the building while heat is ultimately rejected using a separate system that may or may not consume water.
Two figures deserve attention. Water withdrawal is the amount taken from a river, aquifer or municipal supply. Water consumption is the amount not returned to that source, often because it evaporates. A site might withdraw a large volume but return most of it, or use a smaller supply with a higher proportion lost. Those are different pressures on local resources. Reclaimed wastewater can reduce demand for drinking water, though it still needs infrastructure and treatment. The consequences also change with the season: peak cooling requirements may arrive exactly when a region is experiencing drought or household demand is high.
We've encountered project statements that describe efficiency without supplying the figures needed to compare facilities. A litres-per-computation claim can be useful for an engineering team but doesn't tell a resident how much water the site needs in a hot month. A large annual estimate with no named source is similarly incomplete. Site-specific answers need expected peak and annual withdrawal, consumption, water source, cooling method and any upgrades to local treatment or distribution systems.
The comparison we want is not which centre uses the smallest number in isolation. It is whether water use is measured, appropriate to local availability and accurately described. A data centre using reclaimed water in a well-supplied region presents a different situation from one drawing drinking water from an already constrained system. We should have enough evidence to see that difference.
These explainers separate announced plans, recorded outcomes and unresolved questions. Find individual facility sources and submit corrections in the Observatory.
General background: IEA, Energy and AI. For site-specific claims, consult each facility's source records.