Water has become a flashpoint in debates over data centers. Reports of massive water use have fueled community protests from Arizona to the Netherlands over fears that data centers are draining local water supplies. These concerns are understandable: one large facility can use as much water as a small city. However, the full story of data center water usage is more nuanced.
In this article, we’ll break down myths vs. reality around data centers and water. We’ll clarify what “water usage” really means in this context, the types of cooling systems (from evaporative cooling towers to closed-loop recycled water systems), how much water is actually consumed vs. returned, and whether data center water use truly deprives communities of drinking water. We’ll also highlight new trends (like using recycled wastewater for cooling ) and explain why water quality (not just quantity) is the often-overlooked piece of the puzzle.
The goal is an accurate, empathetic look at data center water use: cutting through hype, sharing facts, and identifying sustainable solutions. Let’s start by understanding how and why data centers use water at all.
How Data Centers Use Water: Cooling is Key
Unlike most industries, data centers don’t use water as a raw material. They use it to keep servers cool. Thousands of servers packed in racks generate enormous heat, and cooling is critical to prevent overheating or even equipment failure. There are several cooling methods in use:
- Air cooling (water-free): Many smaller or older data centers rely on air conditioning and chilled air circulation to remove heat. These use mechanical chillers or heat exchangers and do not consume water for cooling (aside from minimal water for humidification). Air cooling is common in cooler climates or where water is scarce, but it can require more electricity to run compressors or fans.
- Evaporative cooling (open-loop): A majority of large, modern data centers use water-based cooling for better energy efficiency. This often involves cooling towers or evaporative chillers: warm water absorbs heat from servers and is then cooled by evaporation in a tower. As water evaporates into the air, it carries away heat – dramatically cutting the electrical power needed for cooling. The trade-off is high water consumption. Most big data centers today use some form of evaporative cooling because it’s energy-efficient, especially in hot climates, but it directly uses water (often drawn from municipal supply).
- Closed-loop water cooling: In closed-loop systems, water circulates in sealed pipes or coils that cool the servers without directly exposing water to air. Because the water isn’t evaporated to the environment, losses are minimal – it’s mostly the same water recirculating (with some makeup water added occasionally). These systems can include water-cooled heat exchangers or liquid-to-liquid cooling loops. Closed-loop cooling can reduce freshwater use by up to 70% compared to traditional open evaporative methods. The downside is higher cost and complexity, but they are far more water-efficient since water isn’t “burned off” into the air.
- Direct liquid cooling & immersion: An emerging category is liquid cooling at the server or chip level. Direct-to-chip cooling uses cold liquid (water or special coolant) piped directly to server CPUs/GPUs, and immersion cooling submerges whole servers in a bath of non-conductive fluid. These methods transfer heat very efficiently and can significantly reduce water usage. Typically, they still need a heat exchange system to reject heat (often a dry cooler or a closed-loop water circuit), but because they target heat more directly, they require less bulk air conditioning. Immersion and direct liquid cooling are gaining traction for high-density AI and HPC (high-performance computing) data centers, especially in water-limited areas. In areas with scarce water, liquid cooling is ideal as it uses minimal water, whereas in areas with strained power grids, evaporative cooling is favored for using less electricity. This highlights a key point: there’s a water–energy tradeoff. Saving water often means using more electricity for cooling, and vice versa.
- Free cooling: In cold climates, some data centers simply use the outside air or cold water sources for cooling. For example, drawing chilly air into the facility or using adjacent river/sea water in a heat exchanger (sometimes called water-side economization) can eliminate a lot of active cooling. Free cooling is highly efficient and water-free, but it only works in certain climates or seasons. (Not many data centers are in the Arctic. Most are near population centers where free cooling is a limited but valuable technique.)
Each cooling approach has a different profile of water usage. So when we talk about a data center’s “water use,” it could range from virtually zero (an air-cooled facility on a cool day) to millions of gallons (a large evaporatively-cooled campus on a hot day). Next, let’s look at how prevalent each type is and what “water use” really entails in each case.
Water Usage by the Numbers: Who Uses What (and How)
Most data centers do use water in some form, but not all. Industry estimates show that roughly 75–90% of data centers worldwide rely on water-based cooling as their primary method. In other words, only about 10–25% are completely water-free (using only air or refrigerants for cooling). Among the water-cooled facilities, the vast majority of large-scale data centers use open-loop evaporative cooling meaning they evaporate water as part of the cooling process. This has been the standard because it’s effective and energy-saving, but it does consume water.
What about using non-drinking water? Unfortunately, most of that cooling water has historically come from potable (drinking-quality) sources like municipal water or groundwater. One analysis estimated that around 57% of data centers’ direct water use is from potable water supplies. Another industry assessment was even starker: 80–90% of water used by data centers is drawn from “blue” water sources such as lakes, rivers, or aquifers – often the same sources providing community drinking water[15]. In practice, many data centers simply hook up to the local water mains. For example, Loudoun County, Virginia – the world’s largest data center hub – supplied around +/-1 billion gallons of water to data centers in 2023, mostly relying on treated potable water because reclaimed water capacity was insufficient. This is why local residents get concerned: if a data center is using city water, that could be water that otherwise serves homes, especially in a drought.
However, a growing number of data centers are now shifting to recycled water. Tech giants have begun partnering with utilities to use treated wastewater (effluent) for cooling instead of fresh drinking water. For instance, Google uses reclaimed or non-potable water at over 25% of its data center campuses (one notable example is its Douglas County, Georgia data center, which runs on recycled municipal wastewater). Amazon Web Services (AWS) announced in 2023 that 20 of its data centers are cooling with purified wastewater instead of potable water. After cycling through the cooling system, this water is sent back to the treatment plant to be cleaned and reused again. These initiatives leave more drinking-quality water for the community and exemplify the industry’s trend toward “strategic water sourcing.” Still, as of today, reclaimed water use is the exception. Most data centers worldwide are still using fresh water for cooling, although this is slowly changing with new projects and local regulations.
So how much water are we talking about? Water use varies widely by the data center’s size, design, and location:
- A medium-sized data center might consume on the order of +/-100 million gallons per year for cooling. (If the average American household uses 300 gallons/day, a mid-size data center would require the equivalent of ~1,000 U.S. households annually).
- Large hyperscale facilities (think of the huge cloud data centers) can use 1 to 5 million gallons of water per day under peak conditions. At the upper end (5 million gal/day), that is as much water in a day as a town of 30,000–50,000 people would use. That startling stat often grabs headlines. However, it’s worth noting this would be a very large data center on a hot day; typical usage might be lower most of the year.
- Nationally, the aggregate impact is significant but not enormous compared to other sectors. All U.S. data centers combined were estimated to consume about 449 million gallons of water per day (1.7 billion liters) as of 2021. That’s roughly 0.3–0.4% of total U.S. daily water withdrawals – a small slice compared to agriculture or power generation. But importantly, data center water use tends to be concentrated in specific regions (often arid or suburban areas), so the local impacts are outsized even if the national percentage is small. About 40% of U.S. data centers are located in areas of high or extreme water stress, meaning those communities really feel each gallon.
Water consumption vs. water withdrawal: It’s crucial to distinguish these terms. When a data center “withdraws” water, that’s the amount taken from the source (e.g. pumping from the city water line). “Consumption” means water that’s actually used up (not returned) – primarily through evaporation. The difference (withdrawal minus consumption) is the water returned, usually as wastewater (warm water or “blowdown” drained from cooling systems). In a data center cooling context, most of the water that is withdrawn ends up consumed. Typically, 70–80% of the water in evaporative cooling is lost as evaporation into the air. The remaining 20–30% is discharged as liquid wastewater (which goes to a sewer or treatment plant). For example, if a site draws 1000 gallons, roughly 700–800 gallons might evaporate through the cooling towers (this portion is gone from the local water system until it falls again as rain), while 200–300 gallons exit as effluent that can potentially be treated and reused downstream. This means not every gallon taken is a gallon gone – but a large fraction is effectively consumed.
Closed-loop systems change this equation: because they don’t intentionally evaporate water, their consumption is far lower. A closed-loop cooled data center might only consume on the order of 5–10% of its water withdrawal (losing small amounts to leaks or incidental evaporation), returning ~90–95% as wastewater available for treatment. And an air-cooled data center consumes virtually zero water on-site (aside from perhaps some landscaping or restroom use by staff). So, water consumption ranges from nearly 0% to nearly 80% of water withdrawn, depending on the cooling design. The industry-average Water Usage Effectiveness (WUE) has been reported around 1.8 liters per kWh (i.e. 1.8 L of water evaporated per kWh of IT energy), though top designs aim much lower. In practical terms, data centers can evaporate 1–9 liters of water per kWh of energy used; the low end (~1 L/kWh) is achievable with efficient cooling and climate, whereas the high end applies to less efficient sites in hot climates.
To sum up: most data centers today do use water, mostly from fresh supplies, and much of it is consumed via evaporation. But not all water use is equal – some facilities use recycled water, some return a lot of water, and some use hardly any water at all. With this understanding, let’s tackle some of the biggest myths vs. realities swirling around this topic.
Myth vs. Reality: Data Center Water Edition
To separate fact from misconception, here’s a breakdown of common myths about data centers’ water use and the realities:
Myth
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Reality
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“Data centers are water guzzlers draining our towns dry.”Data centers are often accused of destroying local water supplies.
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Context matters:Yes, data centersuse a lot of water, but they are not all alike.Alarge facility can withdraw millions of gallons a day, yet others use hardly any. Nationally, all U.S.data centers use <1% of waterwithdrawals. However,local impacts can be seriousin water-scarce areas – e.g. one Oregon town found Google’s data centers tookover 25% of the city’s water supplyin 2021. So, data centerscanstress local water, but itdepends on the location, cooling method, and water sourcing. Many modern data centers are mitigating this by using alternative water sources and more efficient cooling.
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“Every gallon a data center uses is a gallon less for the community.”People often assume water used by a data center is permanently lost to locals.
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Not exactly – not all water withdrawn is consumed.On average,20–30% of the waterdata centers use for cooling isreturned as wastewater(not immediately drinkable, but still in the water cycle). Only the portion that evaporates (often ~70+%) is truly “consumed” and removed from local supply. Moreover, some data centers usenon-potable sources–reclaimed wastewater or seawater– so they’re not taking from the community’s drinking water reserve.Reality:A data center’s impact on community water supply can range from significant (if it’s drawing potable water and evaporating most of it) to minimal (if it’s using recycled water or returning most water after cooling).
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“Data center water use is basically one-way – all that water just vanishes.”
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In cooling, much water does evaporate, butsome returnsand can be reused. For example, in aclosed-loop cooling system, water is recirculated multiple times,significantly reducing net usage. Even in evaporative systems, theblowdown water(leftover after evaporation) is sent to wastewater treatment and can re-enter circulation (after treatment) for other uses. Think of it this way: if a data center withdraws 100 million gallons in a year and 30% is discharged, that’s 30 million gallons going back to be cleaned –not truly gone(though not immediately drinkable either). So it’s not pure “water vapor into thin air” for all of it.
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“If a data center uses water, local residents will have less to drink.”
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Not a foregone conclusion – source and management are key.Many data centers, especially new ones, strive toavoid using municipal drinking water for cooling. They tap intoalternative water sources: for instance, using treatedeffluent (sewage water)thatisn’t fit for drinking, orbrackish groundwaterthat isn’t used for homes. This means the data center’s thirst doesn’t directly compete with the public’s. Even when potable water is used, it’s often in places where the supply is ample – and increasingly, communitiesrequire data centers to offset or replenish water. (BothGoogleandMicrosofthave pledged toreplenish more water than they consume, effectively aiming to give back water to local environments.) So,data centers don’t inherently mean less drinking water– it comes down to how responsibly the facility is designed and integrated into local water plans.
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“Data centers waste water in inefficient systems – it’s all old-school cooling towers.”
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This used to be mostly true, but is changing fast.It’s correct that most large data centers today useevaporative cooling, a decades-old method. But thetrend is toward water-efficient tech. Examples:closed-loop coolingthat cuts water loss by ~70%;direct liquid coolingat the server level which drastically lowers the need for evaporation;free-air coolingin cooler climates; andusing recycled waterinstead of fresh. Big cloud operators are innovating:Microsoftis raising server room temperatures so it can usezero-water coolingin many regions;Googlealready uses non-potable water at a quarter of its sites and plans toreplenish 120% of the water it uses;Amazonis retrofitting dozens of data centers to usereclaimed waterby 2030. In short, the industry knows water is a critical issue and israpidly deploying newer cooling designsto use less water per unit of computing. The days of wanton water use are numbered, driven by both environmental and business pressures.
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“Water usage is the only water issue with data centers.”The public debate focuses on how much water is used.
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Reality: waterqualityand wastewater are the “elephant in the room.”While everyone talks abouthow many gallons, fewer talk aboutwhat’s in the waterand where it goes. Data centers that use water for cooling producesubstantial wastewater– which can contain treatment chemicals (biocides, anti-corrosion agents), concentrated minerals (scale), and even heavy metals picked up from the system. If thisdischarged waterisn’t managed properly, it canpollute local waterways or overburden sewage treatment plants. In some cases, spikes in discharge from a data center have strained municipal water treatment capacity, raising concerns about water quality for the community downstream. This is why some municipalities now require data centers topre-treat their wastewater on-site– essentiallyinstalling mini water treatment facilities– before releasing it.Monitoring water qualityin real-time is emerging as a priority so that anycontaminants or parameter spikes are caught earlyIn short, focusing only on how much water is used misses half the story:making sure the water that’s returned is clean and safely managed can be even more critical for protecting community water resources.
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As we see, there are kernels of truth in the “myths” but also important realities that paint a more balanced picture. Yes, data centers consume water and can impact local supplies – but many are working to minimize that by using recycled water and efficient cooling. And no, data center water use isn’t purely zero-sum against residents if managed wisely. Perhaps most importantly, the quality of water leaving the data center deserves just as much attention as the quantity coming in.
New Trends: Toward Water-Smart Data Centers
The good news is that the industry is pivoting to reduce water footprints – both to be a good neighbor and because water costs/constraints are becoming a business risk. Here are some notable trends and solutions gaining momentum:
- Use of Recycled Water: As mentioned, companies are forging partnerships to use reclaimed wastewater or “grey water” for cooling. This means tapping city sewage outflow, treating it to an appropriate level, and using that instead of fresh potable water. Example: AWS in Virginia now cools many data centers with treated wastewater, and after use, the water goes back for re-treatment and reuse. This circular approach greatly lessens demand on the freshwater system. Many cities welcome this, as it creates a use for effluent and often comes with infrastructure investments paid by the tech firms. Google, Microsoft, Amazon, Meta, and others have all announced recycled-water projects at various data center locations. These projects are expanding – Amazon plans to use recycled water in over 120 data centers by 2030, saving an estimated 530 million gallons of fresh water per year.
- Closed-Loop and “Waterless” Cooling Designs: Engineers are finding ways to avoid evaporation altogether. Microsoft recently unveiled data center designs optimized for AI hardware that use zero water for cooling – even in desert climates. They achieve this by combining liquid cooling on chips with air cooling for heat rejection, and by allowing higher operating temperatures. In general, raising the temperature set-point means chillers or wet coolers are needed far less, as Microsoft demonstrated – they expect to eliminate water use for cooling in several major regions (like Northern Virginia and Ireland) and cut water use in Phoenix-area (desert) data centers by up to 60% just by these design tweaks. Other companies are exploring adsorption chillers, geothermal cooling, and other novel tech to ditch the cooling tower paradigm entirely.
- Efficient Water Management: When water is used, new techniques aim to use each drop more productively. For example, data center operators now often increase the “cycles of concentration” in cooling towers – using chemical or physical water treatment so that the same water can be recirculated more times before it must be bled off. This can cut total water consumption significantly. Digital Realty, a data center provider, used an electrolytic process in one Singapore site that let them reuse water 3× more before discharge. Others have added filtration systems to remove minerals and allow continual reuse. These measures reduce the need for fresh makeup water.
- Alternative Cooling Methods: Immersion cooling and direct-to-chip liquid cooling (using dielectric fluids or water in closed loops) are gaining adoption for high-density racks. They can drastically reduce the reliance on large-scale chilled water or HVAC systems. Immersion cooling in particular, because it captures heat in a controlled fluid system, may only require a dry cooler (no water) to dump heat externally – making it a water-sparing solution for the future of supercomputing. It’s still early days, but as AI computing grows, these techniques are expected to become more common.
- Renewable Energy = Indirect Water Savings: Interestingly, using renewable energy for data centers also saves water. How? Traditional power plants (coal, gas, nuclear) use vast amounts of water for cooling and steam – in fact, cooling power plants is a larger water use than the data center’s direct cooling in many cases. If a data center runs on solar or wind power, virtually no water is used to produce that electricity (unlike a coal plant which might use 20,000 gallons per MWh generated). So as data centers shift to renewables for energy (a trend well underway), they indirectly eliminate a huge hidden water usage from the grid. One study estimated that in 2023, U.S. data centers’ indirect water footprint via power plants was about 211 billion gallons – far exceeding the on-site water use. By decarbonizing, data centers help slash that indirect water drain, which benefits overall water availability.
- Monitoring and Accountability: Only about half of data center operators tracked their water use as of 2021, but this is changing. Investors, regulators, and communities are demanding transparency. New reporting standards (like a recent EU mandate for data center resource reporting) and industry metrics (like WUE) are pushing operators to measure and publicly share water usage data. This transparency drives competition to improve and also reassures stakeholders that water is being managed. Real-time monitoring of water flows and quality is becoming part of best practices – for example, installing sensors to continuously check for any leak, abnormal usage spike, or water chemistry issue. This not only helps optimize efficiency but also prevents environmental incidents (like discharging poor-quality water by accident).
- Community Water Projects: To maintain a good relationship (and social license to operate), the big tech companies are also investing in local water conservation projects. “Water positive by 2030” doesn’t only mean reducing their own use – it also means funding replenishment of aquifers, habitat restoration, stormwater capture, and community water programs to add back water. For instance, Google has funded projects to restore wetlands and improve groundwater recharge in regions where it operates, aiming to replenish 120% of the water it consumes. These efforts help offset the impact of their water withdrawals and improve overall water resilience for the community.
In combination, these trends indicate a future where data centers can grow without proportionally increasing their water draw. A next-gen data center might use minimal freshwater, rely on circular water systems, continuously monitor its water quality, and even contribute net positive water to its region. We’re not completely there yet industry-wide, but the movement is clearly in that direction.
The Overlooked Priority: Water Quality and Real-Time Monitoring
It bears repeating: while reducing water usage is important, protecting water quality may yield even greater bang for the buck in many communities. A data center can be designed to use 50% less water, but if it inadvertently pollutes a river or overloads a sewage plant, the harm to the community can be far worse than the volume of water consumed.
Consider that cooling tower blowdown (the water bled off from cooling systems) tends to have high mineral content (TDS), traces of chemicals like chlorine or biocides, and altered pH. If dozens of data centers in one area are all discharging such water, the local wastewater treatment facility faces a huge load. In Northern Virginia’s data center alley, for example, the volume of wastewater from data centers is so large that utilities are closely watching capacity. Overtaxed treatment plants could lead to insufficiently treated water reaching streams, which threatens aquatic life and public health. Moreover, thermal pollution is a factor: data centers sometimes release water that’s significantly warmer, which can upset the ecology of rivers or lakes if not cooled.
This is why real-time water quality monitoring is emerging as a critical tool. By continuously tracking parameters like pH, conductivity, chlorine levels, metals, etc., data center operators (and utilities) can ensure that any discharge stays within safe limits. If a reading spikes – say, higher temperature or a chemical imbalance – they can take immediate action (e.g., divert to an on-site treatment system, or adjust chemical dosing). Such proactive monitoring gives an extra layer of protection to the community’s water. It’s essentially applying the same diligence to water as data centers already do to energy and uptime monitoring.
Some data centers are going a step further and implementing on-site wastewater treatment or recycling. For instance, Google’s Georgia data center not only uses reclaimed water for cooling but also treats its own wastewater on-site to a level that it doesn’t need to send it to the municipal sewer at all. By treating and then reusing or safely releasing water themselves, data centers can greatly reduce the burden on public infrastructure. This kind of innovation may become standard in water-stressed regions: the data center of the future might have a built-in water recycling plant, ensuring almost no drop of water leaves it without being cleaned and reused.
From a community perspective, focusing on water quality can yield quick wins. Improving wastewater treatment and monitoring can often be done faster and cheaper than, say, sourcing a whole new water supply. It’s about risk prevention: avoiding contamination events maintains public trust and safety. In contrast, reducing water quantity usage is a more gradual process of efficiency gains. Both are important, but water quality is sometimes underemphasized in public debates. For community advocates concerned about a new data center, it might provide more immediate benefit to ask “How will you monitor and treat the water you use?” in addition to “How much water will you use?”
Conclusion: Finding a Balance Between Bytes and Drops
Data centers are here to stay – they are the backbone of our digital life, from streaming movies to powering AI applications. But they also represent a new type of industrial water user popping up in our communities. The challenge, and opportunity, is to manage this with clear eyes and smart strategies.
Myth-busting the water usage issue shows that while data centers do use significant water, the worst fears can be mitigated with technology and good policy:
- Most of a data center’s water use is for cooling, and much of that can be recirculated or replaced with non-potable sources given the right investments.
- Water consumed is not the same as water withdrawn – efficient systems can return a large share of water for reuse, and innovation is driving that share higher.
- Data centers don’t have to compete with communities for fresh water: with planning, they can tap alternate sources or even augment local water supply (via replenishment projects and avoiding potable water use).
- The industry is already moving toward lower water footprints due to cost, climate, and corporate responsibility goals – witness the big players aiming for “water positive” operations and cutting cooling water by huge percentages.
- And critically, focusing on water quality safeguards ensures that even if a data center uses a lot of water, it won’t harm the environment or public health with its output. This is where real-time monitoring and collaboration with water authorities make a difference.
In crafting a sustainable path forward, facts and transparency are our allies. It’s encouraging that more data is being shared, like how many gallons data centers use and where it comes from, and that stakeholders are engaging in informed discussions rather than knee-jerk reactions. Communities have valid concerns, and data center operators are increasingly acknowledging those and working on solutions (e.g. municipal agreements to use reclaimed water, pledges to restore water, noise and traffic mitigation, etc.).
In the end, it’s not Data Centers vs. Local Water in a zero-sum game. It’s about smart water management. With the right cooling designs, sourcing choices, and quality controls, data centers can exist as responsible water stewards rather than water hogs. They might even become hubs for water recycling innovation that benefits their towns.
For those of us in the tech and sustainability space, this is a chance to spread awareness and champion best practices. Yes, call out the myths that lead to misunderstanding – but also push the industry on the realities that need improvement. The next time you hear someone say “those servers are drinking our water,” you can reply: “They do use water, but here’s how we can make sure it doesn’t hurt our community – and even improve our water situation.” Grounded in facts and proactive in approach, we can ensure that our digital thirst doesn’t exacerbate our water scarcity challenges.
The reality is that data centers and communities can thrive together – but it will take innovation, transparency, and diligent water management to get it right. Let’s keep the conversation factual and solution-oriented, because both our bytes and our drops are precious.