Data centre water: what gets measured An animated diagram in seven steps showing on-site, off-site and supply-chain water for a data centre, the difference between water withdrawn and water consumed, and what the WUE metric counts. river or lake 3Supply-chainwater chips and servers 2Off-site water electricity withdrawn returned consumed Data centre heat 1On-site water town supply cool warm evaporates discharged withdrawn consumed WUE only counts this

Every online service runs on servers that get hot

Cooling them takes water, and that water gets counted in three different places.

On-site water cools the servers

Scope 1: the water a data centre uses directly, at its own site.

Off-site water makes the electricity

Scope 2: used at the power station, on the data centre's behalf.

Supply-chain water makes the hardware

Scope 3: used in manufacturing, before a server is ever switched on.

Withdrawn is not the same as consumed

Two ways to count the same water, with very different totals.

The usual metric counts only one of the three

Water Usage Effectiveness (WUE) stops at the data centre fence. A variant, WUE source, adds off-site water.

Ask what a water number counts

The same data centre can report very different figures, all of them true.
Chat, streaming and office apps all live in data centres, where servers turn electricity into heat.
Water carries the heat away. Where sites cool by evaporation, some of it leaves as vapour.
Many power stations need cooling water too. How much depends on how the electricity is made.
Making chips and servers takes water too, including the ultra-pure water used in chip fabrication.
Withdrawal is everything taken from a source. Consumption is the part not discharged back.
WUE = annual on-site water (litres) รท IT equipment energy (kWh). Scope 2 and 3 sit outside it.
Which of the three does it count? And is it withdrawal or consumption?

Definitions: Li, Yang, Islam and Ren, "Making AI Less Thirsty" (Communications of the ACM, 2025); The Green Grid, Water Usage Effectiveness (2011).