# Water · Data Center Evidence

> Cooling design and water reuse give communities practical ways to accommodate new computing. Follow the heat, the water source and the local supply to understand a project's demand.

By Nate Morton · 2026-10-08 · [Data Center Evidence](https://lfkai.town/evidence/)

Web version: https://lfkai.town/evidence/water/

In Loudoun County, Virginia, treated wastewater supplies industrial cooling and irrigation. [Loudoun Water built its first reclaimed-water pipelines in 2010](https://www.loudounwater.org/commercial-customers/reclaimed-water-program) to serve those uses, including the growing data-center industry. For 2025, the utility reports delivering more than 750 million gallons of reclaimed water to its customers, saving an equal amount of potable drinking water.

Reclaimed water supplies cooling without drawing on the drinking-water system. Cooling equipment offers other choices: engineers can move heat with evaporating water, recirculating liquid or systems that release heat to the air.

A data center's water demand follows those choices, along with its size, workload and climate.

## What “using” water means

Most headlines about data-center water lump three different things together.

**Withdrawn** water is taken from a river, well or city system. Most of it goes back: the U.S. Geological Survey calls the returned part *return flow*, water that reaches a river or aquifer again and becomes available for reuse ([USGS](https://mn.water.usgs.gov/infodata/wateruseconcepts.html)). A shower works this way, and so do most factories and power plants.

**Consumed** water is the part that leaves the local system, mostly by evaporating. It rises as vapor and returns as rain.

**Recirculated** water stays in a closed loop. It is filled once and goes around and around, like the coolant in a car.

Data centers that cool by evaporation consume the water that evaporates. Virginia's auditors found they “typically discharge only a small portion” of the rest, and that discharge goes to permitted wastewater treatment before returning to a river ([JLARC](https://jlarc.virginia.gov/pdfs/reports/Rpt598.pdf)). Closed-loop and air-cooled designs consume very little cooling water.

## Water in scale

All of Virginia's data centers together used about 2.1 billion gallons of water in 2023, just over a third of it reclaimed wastewater rather than drinking water. That is less than half a percent of the state's withdrawals. For comparison, the state's single largest industrial water user drew about 36.5 billion gallons that year ([JLARC](https://jlarc.virginia.gov/pdfs/reports/Rpt598.pdf)).

Nationally, farm irrigation consumes about 73 billion gallons a day and power plants about 4.3 billion ([USGS](https://pubs.usgs.gov/publication/cir1441)). LBNL estimates that U.S. data centers directly consumed 66 billion liters of water in 2023, about 17.4 billion US gallons—about what irrigation consumes in six hours. It separately estimates nearly 800 billion liters, about 211.3 billion gallons, consumed at the power plants that made those facilities' electricity ([LBNL](https://eta-publications.lbl.gov/sites/default/files/2024-12/lbnl-2024-united-states-data-center-energy-usage-report.pdf)). Every electricity customer—homes, hospitals, factories—carries that kind of power-plant water; data centers used about 4.4% of U.S. electricity in 2023. Together, the two estimates come to roughly 228.8 billion gallons for the year: about three days of U.S. farm irrigation.

Food isn't the only comparison. Americans use nearly 8 billion gallons a day watering lawns and landscapes ([EPA](https://www.epa.gov/watersense/outdoors)), household leaks waste nearly 1 trillion gallons a year ([EPA](https://www.epa.gov/watersense/fix-leak-week)), and leaking city water mains lose about 6 billion gallons of treated water a day ([ASCE](https://infrastructurereportcard.org/imagine-a-day-without-water-our-most-valuable-resource/)). Golf courses applied about 1.63 million acre-feet of water in 2024 ([HortTechnology](https://doi.org/10.21273/HORTTECH05716-25)).

```bars
title: Yearly U.S. water totals, billion gallons
Farm irrigation (consumed) | 26,700
Industry (withdrawn) | 5,400
Lawns and landscaping | 2,920
City water mains, leaks (treated water lost) | 2,190
Power plants (consumed) | 1,570
Mining (withdrawn) | 1,460
Household leaks | 1,000
Golf courses (applied) | 531
Data centers, including water for their electricity | 229 | highlight
Data centers, direct use | 17 | highlight
note: Irrigation, industry, mining and power plants: USGS, 2015. Lawns and household leaks: EPA WaterSense. Water mains: ASCE, 2021. Golf: HortTechnology, 2024. Data centers: LBNL, 2023. Consumed water evaporates or leaves the local system; withdrawn and applied totals include water that returns.
```

Cooling efficiency and the electricity supply both shape computing's water footprint.

For a single building: most Virginia data centers used about as much as a large office building, 6.7 million gallons a year, or less. The largest used more than 50 million gallons. U.S. farms apply an average of 1.5 acre-feet of water per irrigated acre ([USDA](https://cropwatch.unl.edu/2024/2023-irrigation-and-water-management-data-now-available)), so 50 million gallons is about a year's irrigation for 100 acres. In Lawrence, which averaged 10.5 million gallons a day from 2015 to 2024 ([Lawrence Journal-World](https://www2.ljworld.com/news/city-government/2026/apr/04/some-leaders-are-now-stating-a-new-reason-for-why-lawrences-utility-rates-are-soaring-the-city-didnt-grow-enough/)), a typical 6.7-million-gallon building would equal about 0.2% of the city's yearly water.

## How cooling uses water

Servers turn electricity into heat. Cooling systems carry that heat away from the equipment and release it outside.

In an evaporative system, water absorbs heat and some of it evaporates. The facility needs replacement water to keep the process going. Other designs circulate liquid through a closed loop and reject heat through equipment that releases it to the air, sometimes with water-assisted cooling in hot weather. Some combine methods and change how they operate with the weather.

[Lawrence Berkeley National Laboratory's report](https://eta-publications.lbl.gov/sites/default/files/2024-12/lbnl-2024-united-states-data-center-energy-usage-report.pdf) explains these configurations. Dry coolers release heat to outdoor air; some add water-assisted cooling during hotter conditions. Airside economizers use outdoor air when the weather allows, reducing the need for mechanical refrigeration.

The full heat-removal path matters. Liquid flowing past a chip tells you how heat leaves the server. The equipment that releases that heat outdoors tells you whether the facility evaporates water. A description such as “liquid-cooled” does not specify both parts.

## What operating records show

[Virginia's Joint Legislative Audit and Review Commission](https://jlarc.virginia.gov/pdfs/reports/Rpt598.pdf), or JLARC, examined 2023 records from utilities serving the large majority of the state's data centers. Most buildings used about as much water as an average large office building or less, and some used less than a typical household. Eleven buildings each used more than 50 million gallons, including one at 243 million—about a year's irrigation for 500 acres of farmland.

Those are individual buildings, not whole campuses. Their variation reflects why the cooling plan, building size and computing density are useful information for a local proposal.

Across the six utilities JLARC reviewed, data centers accounted for between 0.2% and 21% of water use after excluding reclaimed water. The industry's share of a particular utility's demand tells a different story from a statewide total. It connects the facilities to the system actually serving them.

## Reuse changes the source of supply

Reclaimed water is treated wastewater reused for purposes such as industrial cooling. It can replace drinking water in a cooling system and reduce the need for additional withdrawals from rivers or groundwater.

Loudoun Water's program shows that this is operating infrastructure, not just a design proposal. Its reclaimed-water network has grown to 20 miles of pipeline. The utility's reported 2025 deliveries cover its customers collectively, including uses beyond data-center cooling.

In Quincy, Washington, Microsoft paid the full $31 million for a city utility that treats and recirculates its data-center cooling water, saving an estimated 138 million gallons of drinking-quality groundwater a year since 2021 ([EPA](https://www.epa.gov/waterreuse/water-reuse-case-study-quincy-washington)).

A reuse system needs suitable treatment, pipes and enough wastewater to supply its customers. JLARC describes the capital costs and the difficulties smaller utilities may face in providing enough reclaimed water. Loudoun Water also makes new connections subject to supply availability and the system's ability to deliver it.

For a community with a suitable wastewater supply, a large cooling customer can provide a reason to explore reuse infrastructure. The utility and developer can work through the capacity, treatment requirements and funding together.

## Designs that avoid evaporation

In its [December 2024 cooling announcement](https://www.microsoft.com/en-us/microsoft-cloud/blog/2024/12/09/sustainable-by-design-next-generation-datacenters-consume-zero-water-for-cooling), Microsoft described a design that circulates water between servers and chillers without evaporating it for cooling. The company scheduled pilots in Phoenix, Arizona, and Mt. Pleasant, Wisconsin, for 2026, with new sites using the design beginning to come online in late 2027.

Microsoft's announcement says its existing fleet would continue using a mix of cooling systems. The new design still uses water for kitchens and restrooms; its cooling loop is filled during construction.

The company also describes an energy tradeoff: replacing evaporative cooling with mechanical cooling increases electricity use. Warmer cooling-water temperatures and efficient chillers help limit that increase. Cooling choices affect both electricity and water use.

## Connect demand to the local water system

Using the terms above, a facility's demand estimate can identify what it measures and separate drinking water, reclaimed water and any direct withdrawals.

Annual volume describes use over a year. Maximum-day demand describes the capacity needed on the busiest day. Weather-sensitive cooling can use water differently across seasons, so dividing an annual total by 365 does not establish the maximum demand.

JLARC explains how Virginia's withdrawal permits use water-source modeling and can require limits during drought. Most of the state's data centers receive water from utilities, which hold the withdrawal permits. Utilities also plan the treatment and delivery infrastructure needed to serve their customers.

These are related responsibilities. The permitted withdrawal, the pipes and treatment capacity, and the demand from homes and other businesses all belong in the supply plan. JLARC reports that utility staff said data centers paid their fair share of the additional infrastructure they required. A local service agreement can show how a particular project funds its connection and any expansion.

## Understanding a local proposal

Start with the cooling specifications, a phased water-demand estimate and the utility's capacity study. The water utility can explain supply and delivery; the withdrawal-permit authority can explain source limits and drought conditions. Planning staff and local commissioners can connect those documents to the development decision and service agreements.

Five questions bring the pieces together:

- How does the complete cooling system release heat, and when does it need replacement water?
- How much drinking water, reclaimed water or directly withdrawn water is needed annually and on maximum-demand days, at each construction phase?
- How does the utility's supply plan accommodate the project alongside other customers, including during drought?
- Who funds connections, treatment or delivery upgrades, and what agreements govern them?
- Where will metered use be reported so residents can compare operation with the estimate?

Cooling design, water source and infrastructure plans determine how a project connects to the local water system. Following them through to the supply plan and metered use shows how the plan performs once the facility opens.

## Sources

- [Reclaimed Water Program](https://www.loudounwater.org/commercial-customers/reclaimed-water-program) — Loudoun Water, 2025 delivery figures; accessed October 5, 2026 (Utility program and reported deliveries)
- [Data Centers in Virginia — Report 598](https://jlarc.virginia.gov/pdfs/reports/Rpt598.pdf) — Joint Legislative Audit and Review Commission, December 9, 2024 (Legislative research and utility records)
- [2024 United States Data Center Energy Usage Report](https://eta-publications.lbl.gov/sites/default/files/2024-12/lbnl-2024-united-states-data-center-energy-usage-report.pdf) — Lawrence Berkeley National Laboratory, December 2024 (National energy and water modeling)
- [Sustainable by design: Next-generation datacenters consume zero water for cooling](https://www.microsoft.com/en-us/microsoft-cloud/blog/2024/12/09/sustainable-by-design-next-generation-datacenters-consume-zero-water-for-cooling) — Microsoft, December 9, 2024 (Cooling-design disclosure and implementation plan)
- [Water-Use Concepts](https://mn.water.usgs.gov/infodata/wateruseconcepts.html) — U.S. Geological Survey, Accessed October 8, 2026 (Federal water-use definitions)
- [Estimated use of water in the United States in 2015 (Circular 1441)](https://pubs.usgs.gov/publication/cir1441) — U.S. Geological Survey, 2018 (2015 data) (National water-use estimates)
- [2023 Irrigation and Water Management Data Now Available](https://cropwatch.unl.edu/2024/2023-irrigation-and-water-management-data-now-available) — University of Nebraska–Lincoln CropWatch, summarizing USDA NASS, 2024 (2023 survey) (National irrigation survey summary)
- [Some leaders are now stating a new reason for why Lawrence’s utility rates are soaring: The city didn’t grow enough](https://www2.ljworld.com/news/city-government/2026/apr/04/some-leaders-are-now-stating-a-new-reason-for-why-lawrences-utility-rates-are-soaring-the-city-didnt-grow-enough/) — Lawrence Journal-World, April 4, 2026 (Local news report on city water use)
- [Water Reuse Case Study: Quincy, Washington](https://www.epa.gov/waterreuse/water-reuse-case-study-quincy-washington) — U.S. Environmental Protection Agency, Accessed October 8, 2026 (Federal case study of an operating reuse utility)
- [Outdoor Water Use](https://www.epa.gov/watersense/outdoors) — U.S. EPA WaterSense, Accessed October 8, 2026 (National residential outdoor water use)
- [Fix a Leak Week](https://www.epa.gov/watersense/fix-leak-week) — U.S. EPA WaterSense, Accessed October 8, 2026 (National household leak estimate)
- [Imagine a Day Without Water](https://infrastructurereportcard.org/imagine-a-day-without-water-our-most-valuable-resource/) — American Society of Civil Engineers, Report Card for America’s Infrastructure, 2021 Report Card estimate (National treated-water loss estimate)
- [Survey of Water Use and Management Practices on US Golf Courses from 2005 to 2024](https://doi.org/10.21273/HORTTECH05716-25) — HortTechnology (Shaddox et al.), 2025 (Peer-reviewed national survey)