The Google data center at Council Bluffs, Iowa. Cooling towers line the length of the building; the water they consume evaporates into the air or returns to local waterways warmer than it left. Image via Wikimedia Commons.
The computing boom is drawing heavily on freshwater — and returning much of what it takes warmer, saltier, and chemically altered. The withdrawal story is now widely reported. The discharge story is not.
There are roughly 11,400 data centers operating worldwide, and about 38 percent of them are in the United States. As of May 2026, industry trackers counted 4,286 across the country, concentrated most heavily in Virginia, Texas, California, Illinois, and Georgia — with more under construction in nearly every state. The buildout is being driven by cloud services, streaming, and, increasingly, artificial intelligence.
Servers packed into racks and running continuously generate enormous heat, and preventing that heat from destroying the equipment is the central engineering problem of a data center. Most large facilities solve it with water. Globally, somewhere between 75 and 90 percent of data centers use water-based cooling, and the majority of large ones use open-loop evaporative systems, in which water is deliberately evaporated to carry heat away. That method is chosen because it saves electricity — which points to the central tradeoff in this industry. Cutting water use generally means burning more power, and cutting power use generally means consuming more water.
Individual facilities vary enormously depending on size, cooling technology, and climate. A medium-sized data center can consume up to 300,000 gallons a day, about what a thousand households use. The largest can draw up to 5 million gallons a day — roughly 1.8 billion gallons a year, comparable to a town of 10,000 to 50,000 people. Loudoun County, Virginia, the densest data center cluster on Earth, used around a billion gallons in 2023, most of it drinking-quality water.
Nationally, the aggregate looked modest as recently as 2021: about 449 million gallons a day, or 0.14 percent of total U.S. water consumption. But that number conceals the problem rather than describing it. Data center water use is spatially concentrated, and the burden falls on specific watersheds and specific aquifers, often in places already under stress.
The source matters as much as the volume. An estimated 57 percent of data centers draw cooling water from potable supplies — treated municipal water or groundwater. Between 80 and 90 percent of that water is taken from lakes, rivers, and aquifers that also serve public drinking water systems. When a facility on the municipal main runs through a drought alongside the town that hosts it, the competition is direct.
Indirect consumption compounds this. Generating the electricity a data center runs on takes water too — thermoelectric power plants use it for their own cooling. Research has found that nearly half of U.S. data center servers are powered at least partly by plants located in water-stressed regions. Even an air-cooled facility that consumes almost no water on site can be drawing heavily on a river a hundred miles away.
Water supply has become the dominant frame for this story. Utilities, county boards, national newspapers, and the companies themselves now argue over gallons withdrawn and gallons consumed. What has attracted far less scrutiny is what happens to the water that comes back out.
Almost all of the public debate treats data centers as a water quantity problem. The water quality problem — thermal discharge, biocides, corrosion inhibitors, PFAS — has barely been reported at all.
Cooling systems do not circulate clean water. They require chemical additives to stop corrosion, prevent mineral scaling, and kill the algae and bacteria that would otherwise colonize the pipes. Those additives typically include biocides, chlorine compounds, glycols, and anti-scaling agents. Some liquid coolants and air-cooling systems rely on refrigerants and fluorinated gases, a class that includes PFAS — the "forever chemicals" that are difficult and expensive to remove from drinking water once present.
Cooling towers also have to be periodically purged. This blowdown water, discharged to prevent minerals from accumulating in the system, can carry concentrated salts and minerals, corrosion and scaling inhibitors, biocides, heavy metals leached from piping, refrigerants, and PFAS. Under the Clean Water Act, facilities discharging directly to waterways may require permits through the National Pollutant Discharge Elimination System — but permitting regimes were not designed with this industry's scale or chemistry in mind, and enforcement capacity varies sharply between states.
Then there is heat. Water returned to a river after passing through a cooling system comes back warmer than it went in. Thermal discharge lowers dissolved oxygen, stresses fish and invertebrates already near their thermal limits, and can trigger algal blooms. For a river running low and warm in late summer — precisely when cooling demand peaks — a thermal load is added at the moment the system can least absorb it.
Groundwater carries its own version of the problem. Heavy pumping lowers water tables, shrinks the baseflow that keeps streams running between rains, and can leave private wells dry. Where leaks, spills, or improper disposal occur, cooling chemicals can enter soil and groundwater directly.
Facility-level water data is often treated as proprietary, and in many jurisdictions it is actively shielded by nondisclosure agreements between operators and local governments. Aggregate national figures exist, and some companies publish voluntary sustainability reporting, but the granular question a river advocate needs answered — how much is this facility taking from this watershed, and what is it putting back — is frequently unanswerable.
That opacity is beginning to be challenged. In Georgia, where 213 data centers now operate and more are being built, bipartisan legislation introduced in January 2026 would bar local governments and authorities from using nondisclosure agreements to conceal the water and electricity consumption of private facilities. Similar transparency questions are surfacing in Virginia, Arizona, and across the Southeast.
The major operators have responded to growing scrutiny with public commitments and data of their own. Google publishes facility-level water use figures and has pledged to replenish more freshwater than it consumes; its Council Bluffs and The Dalles campuses are frequently cited as models of climate-conscious cooling design. Closed-loop systems, which recirculate water in sealed pipes rather than evaporating it, can cut consumption by up to 70 percent. Direct liquid cooling and immersion, in which coolant is piped to the chip or servers are submerged entirely, reduce it further still.
These technologies work, and they are spreading. But they cost more, they are more complex, and they shift consumption toward electricity — which has its own water footprint upstream. Meanwhile the industry's expansion is outpacing its efficiency gains. Best practices for minimizing harm are still being worked out through research, and the environmental, public health, and social consequences of the buildout have not been comprehensively assessed anywhere.
For the rivers themselves, the questions that matter are local and specific: which watershed, how much, when, and what comes back. Those are exactly the questions the current disclosure regime is least equipped to answer.