Reviewed by Yoan Guyon, Managing Director at gbc engineers
As AI training capacity grows, it is putting more pressure on local water supplies, and that surprises people outside the industry. A data center is a computing facility, not a utility.
Most traditional data centers draw directly on municipal drinking water for cooling, and the volumes are large enough that water now matters as much as power in site selection and design.
Yet in many regions it now competes with hospitals, farms and households for the same water source. At gbc engineers, we see the same pattern often. A cooling strategy decided in the first weeks of design sets a facility's water footprint for the next 20 years.
Why data center water use is under pressure now
2 things changed at once. First, servers packed-in so tightly that standard fans and air conditioning could not keep up, pushing operators toward water-based cooling. Second, the public started paying closer attention to how much water and energy data centers use.
Regulators are asking the same question in writing. The EU Energy Efficiency Directive and Commission Delegated Regulation (EU) 2024/1364 requires operators above set thresholds to report Water Usage Effectiveness (WUE) alongside Power Usage Effectiveness (PUE).
Water stress geography makes it worse. Much of the current hyperscale buildout is landing in regions where water was already tight, from the US Southwest to parts of Southeast Asia. Singapore ran into this same problem, and it is worth its own read.
Read more: Air Cooling vs Liquid Cooling for Data Centers
How cooling design shapes a data center's water footprint
Water Usage Effectiveness (WUE) works like a fuel-efficiency rating, but for water instead of gas: the lower the number, the less water it takes to cool the same amount of computing. The cooling technology is what sets that number:
- Evaporative cooling uses the most water. It cools by evaporating water straight from the municipal supply, and a mid-size facility can use up to 400,000 m³ a year (roughly the water use of 1,000 average US households).
- Closed-loop liquid cooling uses less than half as much water. It reuses the same water instead of evaporating it, though it costs more to build and needs extra equipment (CDUs, which move the coolant around).
- Reclaimed or gray water avoids drinking water entirely by using treated wastewater instead. This only works where the local utility already treats wastewater to that standard.
The gap between these comes almost entirely from the cooling technology itself, not from how well a facility is run.
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Highest (approx. 1-2 L/kWh)
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Low-density, cost-sensitive builds
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Closed-loop liquid cooling
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Recirculated, minimal top-up
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High-density AI/HPC racks
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Moderate, varies by supply
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Mature markets with reclamation infrastructure
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It depends more on what already exists on site than on which technology is theoretically best. A new build can target a WUE goal from day one.
A retrofit inherits whatever piping and plant room space the original facility was given. That often decides what is realistically achievable.
Server density is the other deciding factor. Standard racks under about 8 kW rarely need to abandon air or evaporative cooling. AI and HPC racks are a different story: they commonly exceed 30 kW, well beyond what evaporative cooling was designed to handle.
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Favors closed-loop / reclaimed
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Higher upfront, lower opex water risk
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Minimal structural change
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May need floor/plant room upgrade
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Public sustainability commitment
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The structural side of water-based cooling
Reclaimed and closed-loop systems both bring pipe runs and CDUs that need routing and support. The original building was not always designed to provide it.
Retrofitting reclaimed water usually means new penetrations through an occupied slab. Skip the structural coordination step, and a routine upgrade turns into an unplanned review mid-project.
Evaporative cooling towers add their own structural footprint, typically on the roof. That weight has to be accounted for at concept stage, not discovered once the tower vendor sends a spec sheet.
Read more: The Complete Guide to Data Center Cooling
Water risks operators discover too late
- Underestimating permitting timelines. Some jurisdictions treat data center water use as an industrial withdrawal requiring its own permit, and that process can outrun the construction schedule.
- Treating WUE reporting as a formality. Once the EU EED reporting obligation applies, a poor WUE figure is a public number, not an internal one.
- Drought-driven restrictions on withdrawal. Municipal restrictions during drought can apply to data centers with little warning. Facilities without a reclaimed or closed-loop fallback have limited options.
- Underestimating water treatment costs. Closed-loop systems still need treatment to control scaling and corrosion, an easy cost to leave out of an early business case.
What to check before committing to a cooling strategy
- Commission a water availability assessment before finalizing site selection. Local water rights and drought history should shape the shortlist, not just power and land cost.
- Model WUE and PUE together, not in isolation. A strategy that improves one at the cost of the other is not solving the sustainability problem. It is moving it.
- Engage the local water utility early if reclaimed water is on the table. Treatment capacity and pipe access vary by market and cannot be finalized late.
- Review floor loading for cooling towers or CDUs at concept stage, so the structural team is not solving a weight problem after equipment has been ordered.
Conclusion
Water used to be the invisible utility behind a data center's cooling system. AI-driven density growth and public scrutiny have changed that.
The facilities that handle this well treat water, power and structure as one connected design decision from the start. gbc engineers works with data center teams at exactly that stage.
Frequently asked questions
Is water used in the data center industry for cooling?
Yes. Most data centers built with evaporative cooling towers draw directly on municipal water to reject heat, and this remains the most common approach globally.
Do data center cooling systems recycle water?
Many do, though it varies by system. Closed-loop liquid cooling recirculates the same water with only occasional top-up. Evaporative cooling towers, by contrast, consume water rather than recycling it.
Is liquid cooling environmentally friendly?
Generally yes, in terms of water use, since closed-loop cooling posts far lower WUE figures than evaporative systems. It needs more manufacturing and materials upfront, though.
Can data centers be cooled without water?
Yes, through air-cooled systems using refrigerant-based chillers instead of evaporative towers. This avoids water use entirely but is generally less energy-efficient at high densities.
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About us
gbc engineers
is an international engineering consultancy with offices in Germany, Poland, and Vietnam, having delivered 10,000+ projects worldwide. We provide services in structural engineering, data center design, infrastructure and bridge engineering, BIM & Scan-to-BIM, and construction management. Combining German engineering quality with international expertise, we achieve sustainable, safe, and efficient solutions for our clients.
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