Agriculture dwarfs every other sector when it comes to water use, accounting for roughly 92% of humanity’s total freshwater footprint.1Water Resources and Industry. The water footprint of poultry, pork and beef: A comparative study in different countries and production systems The energy sector, manufacturing, and household taps all contribute, but they are fighting over the remaining sliver. What makes global water accounting tricky, and more interesting than a single statistic can convey, is the distinction between water that is withdrawn from a river or aquifer and water that is consumed and never returned.
Why Agriculture Dominates
Growing food is fundamentally an act of converting water into calories. Plants pull water from soil, use it for photosynthesis and nutrient transport, and release most of it into the atmosphere through their leaves. This process, transpiration, is not a design flaw; it is how plants function. On top of that, water evaporates from exposed soil and from irrigation infrastructure like canals and reservoirs. The combined effect is enormous. One global estimate put the consumptive water use for major crops at about 3,800 cubic kilometers per year, and more than 80% of that came from rainwater absorbed directly by soil rather than from rivers, lakes, or wells.2Water Resources Research. Global consumptive water use for crop production: The importance of green water and virtual water
That distinction between rainwater and irrigation water matters. Rainwater that soaks into a field and feeds a wheat crop would have evaporated or been transpired by whatever vegetation grew there anyway. Irrigation water, on the other hand, is actively diverted from rivers and pumped from aquifers, and its use directly competes with cities, ecosystems, and industry. Globally, irrigation is estimated to account for about 70% of all groundwater withdrawals.3Nature. Rapid groundwater decline and some cases of recovery in aquifers globally When people say agriculture “uses the most water,” they are correct whether you count only the blue water pumped from underground or include the green water falling as rain. Agriculture wins both categories by a wide margin.
The Water Cost of Meat and Dairy
Within agriculture, not all food is created equal. Raising animals for meat, eggs, and milk multiplies the water cost because animals eat crops (which already consumed water to grow), drink water themselves, and require water for processing. The average water footprint per calorie for beef is about 20 times larger than for cereals and starchy roots.4Ecosystems. A Global Assessment of the Water Footprint of Farm Animal Products Even when you compare by protein content rather than calories, milk, eggs, and chicken meat still use roughly one and a half times as much water per gram of protein as pulses like lentils and chickpeas.4Ecosystems. A Global Assessment of the Water Footprint of Farm Animal Products
Almost a third of humanity’s entire freshwater footprint is tied to animal products.1Water Resources and Industry. The water footprint of poultry, pork and beef: A comparative study in different countries and production systems That figure puts livestock in the same league as many countries’ total water withdrawal. The implication is straightforward: shifting even a fraction of global diets away from beef and toward plant-based protein would free up water on a scale that efficiency improvements in irrigation alone cannot match. This is not a fringe argument; it is a direct consequence of the arithmetic.
Energy Production and Industrial Cooling
After agriculture, the energy sector is the next big player, though its water story is more nuanced. Thermal power plants, whether fueled by coal, natural gas, or nuclear fission, generate electricity by boiling water into steam and then need to cool the leftover heat. In 2015, global water withdrawal for thermal electricity generation was estimated at about 500 cubic kilometers, of which roughly 290 cubic kilometers was freshwater.5Nature Energy. Global scenarios for significant water use reduction in thermal power plants based on cooling water demand estimation using satellite imagery But only around 25 cubic kilometers was actually consumed; the rest was returned to rivers and oceans, albeit warmer than when it was taken.5Nature Energy. Global scenarios for significant water use reduction in thermal power plants based on cooling water demand estimation using satellite imagery
The type of cooling system a power plant uses often matters more than whether it burns coal or gas. Once-through cooling systems, which pull in river or ocean water, run it past hot pipes, and dump it back, withdraw 10 to 100 times more water per unit of electricity than cooling towers do. But cooling towers, which recirculate water and lose it mainly through evaporation, can consume about twice as much as once-through systems.6Environmental Research Letters. Operational water consumption and withdrawal factors for electricity generating technologies: a review of existing literature Dry cooling, which uses air instead of water, cuts consumption dramatically but is less efficient at generating power and more expensive to build. This tradeoff explains why many power plants in water-stressed regions still rely on evaporative cooling: it is simply cheaper to use water than to lose efficiency.
Hydropower, often labeled “clean,” has its own water problem. Reservoirs behind dams expose vast surface areas to evaporation, especially in hot climates. Those evaporative losses are real water consumption, even though no pump is involved. Globally, evaporation from hydropower reservoirs is estimated at a production-weighted average of about 65 cubic meters per gigajoule of electricity generated.7ScienceDirect (Elsevier / Renewable Energy). Global water footprint assessment of hydropower In arid regions with large, shallow reservoirs, that figure can be much higher, making hydropower surprisingly water-intensive per unit of energy.
What Happens Underground
Much of the world’s irrigation depends on groundwater, and the pace of pumping in key agricultural regions has outstripped natural recharge for decades. Across nearly 1,700 aquifer systems studied worldwide, the speed of groundwater decline correlates strongly with how much of the overlying land is farmed. The fastest drops are concentrated in cultivated drylands, places where rain is scarce and farmers have no choice but to pump.3Nature. Rapid groundwater decline and some cases of recovery in aquifers globally
One way to visualize the problem is through the concept of a groundwater “footprint,” meaning the area of land surface that would be needed to sustain current pumping rates if recharge were the only source. Globally, that footprint is about 3.5 times the actual area of the world’s aquifers.8Nature. Water balance of global aquifers revealed by groundwater footprint The encouraging nuance is that 80% of individual aquifers still have a footprint smaller than their physical area, meaning they are not being overdrawn. The alarming part is that a handful of heavily overexploited aquifers, concentrated in South Asia, the Middle East, and parts of North America, drive the entire global deficit.8Nature. Water balance of global aquifers revealed by groundwater footprint An estimated 1.7 billion people live in areas where groundwater resources or the ecosystems that depend on them are under threat.8Nature. Water balance of global aquifers revealed by groundwater footprint
Since the 1990s, global groundwater use has been increasing faster than surface water use, reflecting both growing demand and the fact that aquifers are the “lender of last resort” when rivers and reservoirs run low.9Earth System Dynamics. Global modeling of withdrawal, allocation and consumptive use of surface water and groundwater resources Building more dams helped mask this trend for most of the twentieth century. Reservoir-supplied irrigation water grew from about 18 cubic kilometers per year at the start of the 1900s to around 460 cubic kilometers per year by century’s end, adding nearly 40% to available surface water supply.10Water Resources Research. Impact of reservoirs on river discharge and irrigation water supply during the 20th century But the era of large dam construction has largely wound down in most countries, and the remaining demand growth is being filled by wells drilled deeper and deeper into finite aquifers.
Virtual Water and the Global Food Trade
When a country exports grain, it is effectively exporting the water that grew that grain. Researchers call this “virtual water,” and it turns international trade into a massive, invisible plumbing network. The volume of water embedded in global food trade more than doubled over a roughly two-decade span, and the trade appears to generate net water savings because food tends to flow from regions where growing it is water-efficient to regions where it would require more water to produce locally.11PubMed Central. Evolution of the global virtual water trade network
That efficiency story is incomplete, though. About 39% of virtual water exchanged for primary crops flows from countries that are more water-scarce than the importing country, creating what researchers have described as an “unfair exchange.”12Scientific Reports. Trade of economically and physically scarce virtual water in the global food network A water-stressed country exporting crops to a water-rich one is essentially sending away a resource it can ill afford to lose. Roughly 11% of the world’s non-renewable groundwater use for irrigation is embedded in internationally traded food, and two-thirds of that exported depletion comes from just three countries: Pakistan, the United States, and India.13Nature. Groundwater depletion embedded in international food trade In other words, aquifer depletion is not only a local farming issue; it is entangled with global supply chains and consumer demand thousands of miles away.
Domestic Water Use and the Leaks You Cannot See
Household and municipal water use looks small next to agriculture, typically around 10% of total withdrawals in most countries. But it is the water use people interact with every day, so it gets outsized attention. Within the home, the single biggest discretionary use is often surprising: lawn and garden irrigation. In the arid western United States, watering the lawn can exceed 50% of total domestic water use.14ScienceDirect (Elsevier). The effectiveness of water irrigation policies for residential turfgrass A similar pattern holds in Australian cities, where lawn irrigation accounts for at least half of all water consumed by the domestic sector.14ScienceDirect (Elsevier). The effectiveness of water irrigation policies for residential turfgrass Showers, toilets, and dishwashers get the scrutiny, but the sprinkler system quietly running at dawn often consumes more than everything inside the house combined.
Even before water reaches your tap, a significant portion disappears. Non-revenue water, meaning water that enters the distribution system but never reaches a paying customer, accounts for staggering losses in many cities. Leaking pipes, unauthorized connections, and metering errors can push losses past 50% in some systems around the globe.15Wiley Online Library. Urban Water Pipe Networks Management Towards Non‐Revenue Water Reduction: Two Case Studies from Greece and Turkey Physical leaks are the dominant component of those losses. In cities with aging infrastructure, reducing pipe leakage is often the single most cost-effective way to “create” new water supply without touching a river or drilling a well.
Emerging Water Demands from Technology
Three technology sectors are drawing increasing attention for their water consumption, even though their current share of global use is small.
Artificial intelligence is the most discussed. AI data centers consume freshwater through evaporative cooling systems, through the electricity they draw from thermal power plants, and through the semiconductor manufacturing that builds their chips. Projections suggest that AI’s global water footprint could reach 4.2 to 6.6 billion cubic meters per year by 2027.16Water Research. The water footprint of artificial intelligence: Emerging solutions and governance imperatives To put that in perspective, agriculture consumes thousands of cubic kilometers annually; a few billion cubic meters is a fraction of a percent of global use. But data centers tend to cluster in specific regions, and their local water demand can strain municipal supplies in places that are already water-stressed.
Semiconductor manufacturing, which underpins AI and the broader electronics industry, is also highly water-intensive. Fabrication plants use ultrapure water in enormous quantities for rinsing silicon wafers, and that water requires extensive treatment before and after use.17PubMed Central. Semiconductor manufacturing wastewater challenges and the potential solutions via printed electronics A single large fab can consume millions of gallons per day, which again is modest at the global scale but can be a major draw in the specific watershed where the facility sits.
Green hydrogen, produced by splitting water with renewable electricity, adds another emerging demand. Electrolysis itself requires roughly 10 liters of water per kilogram of hydrogen, with an additional 10 to 20 liters needed for process cooling.18Energy Conversion and Management. Water-conscious green hydrogen production and conversion for harnessing long-term storage in remote renewable microgrids Current estimates for PEM electrolysis, one of the leading technologies, put total water consumption at about 17.5 liters per kilogram of hydrogen, split almost evenly between the reaction itself and cooling.19WIREs Energy and Environment. Water Consumption in Hydrogen Production Through Electrolysis: Overview, State‐of‐the‐Art, and Future Trends If hydrogen production scales up as many climate roadmaps envision, water sourcing will become a meaningful planning constraint, particularly in arid regions that also happen to have abundant solar and wind resources.
How Climate Change Shifts the Balance
Warmer air can hold more moisture, which generally increases the rate at which water evaporates from soil and transpires from plants. This has led to concern that climate change will ratchet up irrigation demand in agricultural regions that are already water-stressed. The evidence, though, is more mixed than the simple physics might suggest.
One study of irrigated land in California found that warming had only a modest effect on evapotranspiration rates, about 1% per degree Celsius, because plants partially compensate by closing the pores on their leaves when conditions get hot and dry.20Earth’s Future. Will Anthropogenic Warming Increase Evapotranspiration? Examining Irrigation Water Demand Implications of Climate Change in California That stomatal regulation nearly offsets the atmospheric push toward higher evaporation. On the other hand, a broader analysis across North America found that human-caused warming drove a 64-millimeter increase in annual reference evapotranspiration from 1980 to 2022, and that in California’s Central Valley alone, climate change added cumulative irrigation demand equivalent to about 11% of the region’s total groundwater loss over that period.21Earth’s Future. Climate Change Increases Evaporative and Crop Irrigation Demand in North America
The tension between these findings is partly about scale and partly about crops. Reference evapotranspiration, which is a theoretical estimate of how much water the atmosphere “wants” to pull from the surface, has clearly gone up across much of North America. But actual plant water use depends on species, management, and how stressed the plants are. In semi-arid regions that already irrigate heavily, even small percentage increases in demand translate into large absolute volumes because the baseline is so high. And in many parts of Asia and Africa where irrigation is expanding rapidly, rising temperatures are projected to push water requirements higher at the same time that population growth is pushing food demand higher.22Hydrological Processes. Regional impacts of climate change on irrigation water demands
Desalination and the Energy-Water Tradeoff
With freshwater supplies under pressure, desalination often comes up as the ultimate backstop: the oceans hold more water than humanity could ever use, so why not just remove the salt? The answer is energy. The absolute minimum energy needed to desalinate a cubic meter of seawater at room temperature, dictated by thermodynamics rather than by any particular technology, is about 0.79 kilowatt-hours.23Desalination. Sustainable RO desalination – Energy demand and environmental impact Real-world reverse osmosis plants typically use three to four times that much. At industrial scale, that energy bill is substantial, and in many countries it is still generated by burning fossil fuels, which in turn requires cooling water of its own.
Desalination has grown rapidly in the Middle East, North Africa, and parts of Australia and California, and the cost per cubic meter has been falling for decades. But it remains far too expensive to use for irrigation of commodity crops like wheat or rice. It is viable for urban drinking water and for high-value greenhouse agriculture. The fundamental constraint is that agriculture is both the largest water user and the least able to pay for expensive water, which means desalination cannot solve the core problem on its own.
How Dams Reshaped Water Supply
For most of the twentieth century, the answer to rising water demand was straightforward: build a dam. The United States led this approach, constructing thousands of large dams to store water for irrigation, hydropower, and urban supply. Reservoir capacity grew faster than the human population, enabling urban, industrial, and agricultural expansions that would not have been possible otherwise.24PubMed Central. The legacy of large dams in the United States This created a supply-demand cycle: more stored water encouraged more water-intensive activity, which created demand for still more storage.
The legacy of that era is visible in global numbers. Irrigation water supply from reservoirs grew from roughly 18 cubic kilometers per year at the start of the twentieth century to around 460 cubic kilometers per year by its end, adding nearly 40% to the surface water available for farming.10Water Resources Research. Impact of reservoirs on river discharge and irrigation water supply during the 20th century But the best dam sites have largely been built out in most industrialized countries, environmental opposition has grown, and the social costs of displacing communities and flooding ecosystems are now weighed more seriously. In much of the developing world, new dams are still being built, but they face growing scrutiny. The result is that the world can no longer rely on expanding surface storage to keep pace with demand, which returns us to the uncomfortable reality of finite aquifers bearing an increasing share of the load.