The digital thirst: How AI and data centers are draining global water supplies

Only 3% of the world’s water is freshwater, and just 0.5% of that is accessible and safe for human use. Freshwater is essential for life, and on average, a person can survive only three days without it. Droughts and water shortages are making water even less available. At the same time, data center operators are increasingly tapping surface and underground water sources to cool their facilities.

Water use in data centers is closely linked to energy consumption and carbon emissions. As data centers use more energy, they also need more water to cool processors and prevent overheating, which can damage equipment. At the same time, higher energy use leads to higher carbon emissions.

A medium-sized data center can use up to 110 million gallons of water per year for cooling, roughly equal to the annual water use of about 1,000 homes. Larger data centers can use up to 5 million gallons per day, or 1.8 billion gallons per year—enough for a town of 10,000–50,000 people. In the U.S., all 5,426 data centers together use billions of gallons of water annually. A 2021 report estimated U.S. data centers consume 449 million gallons daily and 163.7 billion gallons yearly. A 2016 study found that fewer than a third of data centers track their water use. As data centers grow in number, size, and complexity, water use is expected to keep rising.

According to researchers at the University of California, Riverside, each 100-word AI prompt uses roughly one bottle of water (519 milliliters). While that may seem small, billions of AI users worldwide are entering prompts every minute into systems like ChatGPT. Large language models require energy-intensive calculations, which in turn need liquid cooling systems.

The water cycle of data centers

A data center’s water footprint comes from three main sources: on-site water use, water used at the power plants that supply electricity to the data center, and water used in manufacturing processor chips. Water comes from surface and underground sources (blue water), municipal supplies, and reclaimed or treated water (gray water). In dry areas, using recycled or non-potable water helps conserve limited freshwater supplies.

“Water use” in data centers typically means the water withdrawn from blue or gray sources minus the water returned (mostly warm water from cooling IT racks). Most of this consumed water either evaporates or is no longer directly available for human use. Drawing freshwater from local streams or aquifers, especially in water-stressed areas, can lead to depletion.

The nonprofit industry group The Green Grid created the Water Usage Effectiveness (WUE) metric to track water efficiency in data centers. Similar to the Power Usage Effectiveness (PUE) metric for energy efficiency, WUE measures liters of water used per kilowatt-hour (kWh) of energy consumed. A WUE of 0 is ideal but can only be achieved in fully air-cooled centers. The average WUE is 1.9 liters/kWh.

Data center water use depends on location, climate, water availability, size, and chip density. In hotter regions, like the U.S. Southwest, more water is needed to cool the facility. Higher chip density raises room temperatures, requiring additional water cooling. Most centers use chillers and on-site cooling towers to prevent overheating.

At the server level, water cooling keeps temperatures optimal and protects chips. Cooling can be done through air evaporation (open-loop, water-intensive) or server liquid cooling. Liquid cooling is more expensive but delivers coolant directly to CPUs and GPUs. Two main technologies—direct-to-chip liquid cooling and immersion cooling—significantly reduce water use. In immersion cooling, chips are bathed in water or synthetic fluid that absorbs heat, similar to the difference between drip irrigation and flooding in agriculture.

In water-limited areas, immersion or direct liquid cooling is the best choice. In regions with limited power, evaporative air cooling towers may be more suitable.

All cooling methods require heat exchangers to capture heat from hot water or air. About 80% of water used evaporates, while the rest is discharged to municipal wastewater, which can strain local systems.

A large portion of water use also comes indirectly from energy generation. In the U.S., 56% of data center electricity comes from fossil fuels. Coal plants use about 19,185 gallons per MWh, and natural gas plants about 2,800 gallons per MWh. In 2022, coal and gas plants accounted for 40% of U.S. water withdrawals, roughly 48.5 trillion gallons, of which 962 billion gallons were consumed and unavailable for downstream use. Solar panels and wind turbines, in contrast, require no water for cooling.

Chip and server manufacturing also consume significant water. Each server contains multiple CPUs, GPUs, and memory chips. Producing ultrapure water for chip manufacturing is highly water-intensive: roughly 1,500 gallons of water are needed to make 1,000 gallons of ultrapure water. An average chip factory uses about 10 million gallons per day. By the time a chip reaches a data center, thousands of gallons of water have already been used.

Impacts on local communities

The 5,426 U.S. data centers already affect nearby communities. Northern Virginia, considered the global data center capital, has over 300 data centers across Fairfax, Loudoun, Prince William, and Fauquier counties. In 2023, these centers used nearly 2 billion gallons of water—a 63% increase since 2019. Loudoun County alone, with 200 centers, used around 900 million gallons, forcing the local water authority to rely more on potable water instead of reclaimed sources.

Making data centers more water-efficient

Most data centers rely on blue water and water-intensive air cooling. But there are more sustainable options: closed-loop cooling, immersion cooling, air cooling, and using non-potable water like recycled wastewater. Closed-loop systems reuse water and can reduce freshwater use by up to 70%.

“Free cooling” brings in cold outside air, which works best in cooler climates. Air cooling vents heat away from chips, using minimal water and energy. Immersion cooling submerges servers and chips in dielectric fluids. While upfront costs are higher, it saves water and energy and optimizes space.

Using renewable energy like solar or wind significantly reduces water use compared to fossil fuels. If the U.S. shifted to 100% renewable energy and retired coal and gas plants, billions of gallons of freshwater could be saved for both people and ecosystems.

Source: Environmental and Energy Study Institute