Peer-Reviewed Research on Why Hydroponics Uses 90%+ Less Water

By Grow Space Vertical Farms  •  Kenosha, Wisconsin

The Claim

You've probably heard that hydroponic systems use 90-95% less water than conventional farming. It's a bold claim that deserves scrutiny. So let's break down what the peer-reviewed research actually says.

The Quick Numbers

Here's the range of water usage per head of lettuce:

Growing Method	Water Per Head of Lettuce
Conventional (field-grown)	3 – 13 gallons
Hydroponic	0.3 – 0.5 gallons

At the low end, that's a 10x difference. At the high end — in hot, arid climates like Arizona where much of America's lettuce is grown — it's a 26x difference.

What the Peer-Reviewed Research Says

The most comprehensive study comparing hydroponic and conventional lettuce production comes from Arizona State University, published in the International Journal of Environmental Research and Public Health (2015). The researchers compared lettuce production in Yuma, Arizona — one of the largest lettuce-producing regions in the United States.

The Key Findings

Metric	Hydroponic	Conventional
Water Usage	20 L/kg/year	250 L/kg/year
Water Savings	92% reduction	Baseline
Yield per m²	41 kg/m²/year	3.9 kg/m²/year

Source: Barbosa et al., Arizona State University, International Journal of Environmental Research and Public Health, 2015

That's a 12.5x reduction in water usage per kilogram of lettuce produced. The 90%+ water savings claim isn't marketing it's peer-reviewed science.

Why Does Conventional Farming Use So Much Water?

Understanding where water goes in conventional farming helps explain the massive difference:

•      Evaporation: Open fields lose significant water to the atmosphere, especially in hot climates like Arizona.

•      Runoff: Water that doesn't absorb into the soil runs off and is lost.

•      Soil absorption: Much of the water soaks deep into the ground, past the root zone.

•      Inefficient irrigation: Flood and sprinkler irrigation systems are far less efficient than drip or recirculating systems.

In hydroponic systems, water recirculates through a closed loop. Roots take what they need, and the rest goes back to the reservoir. Very little is lost to evaporation because the system is enclosed.

Common Questions About Hydroponic Water Usage

"Doesn't evaporation still happen in hydroponic systems?"

Yes, but it's minimal compared to open-field farming. Here's why:

•      Enclosed environment: Most hydroponic systems operate indoors or in greenhouses, dramatically reducing exposure to sun and wind.

•      Covered reservoirs: Nutrient solution tanks are typically covered, limiting surface evaporation.

•      Climate control: Indoor farms regulate temperature and humidity, which further reduces water loss.

•      No soil surface area: In conventional farming, water evaporates from the entire field surface. Hydroponic systems have no exposed wet soil.

Some water is still lost through plant transpiration (water released through leaves), but this is inherent to plant growth regardless of method. The key difference is eliminating the massive losses from open-air evaporation and soil exposure.

"What about system flushing? Doesn't that waste water?"

Hydroponic systems do require periodic flushing to manage mineral and salt buildup from nutrient solutions. This is standard maintenance. Here's why it doesn't change the math:

1.    Flushing frequency is low. Most hydroponic systems flush monthly or between crop cycles not daily or weekly.

2.    Flush water is a small fraction of total usage. Even aggressive flushing schedules add only 5-10% to total water consumption.

3.    Flush water can be reused. Many growers use flush water for outdoor gardens, compost, or other non-hydroponic applications. It's nutrient-rich, not toxic waste.

4.    The peer-reviewed studies account for real-world operations. The Arizona State study modeled actual hydroponic greenhouse operations including maintenance water.

5.    The gap is too large to close. Even if flushing doubled hydroponic water usage (it doesn't), you'd still see 80%+ water savings over conventional farming.

"Do these numbers apply everywhere, or just in hot climates?"

Fair question. The Arizona State study was conducted in Yuma one of the hottest, driest agricultural regions in the U.S. Conventional farming there uses more water than it would in cooler, wetter climates.

Here's how climate affects the comparison:

•      Hot, arid climates (Arizona, California Central Valley): Conventional farming uses the most water — 10-13+ gallons per head. Hydroponic advantage is largest here (up to 26x savings).

•      Temperate climates (Midwest, Northeast): Conventional farming uses less water — closer to 3-6 gallons per head. Hydroponic advantage is still significant (10-15x savings).

•      Hydroponic usage stays consistent: Because hydroponic systems are climate-controlled, water usage (0.3-0.5 gallons per head) remains relatively stable regardless of location.

The bottom line: even in the most favorable conventional farming climates, hydroponics still uses dramatically less water. The advantage just gets bigger in water-stressed regions.

It's also worth noting that a significant portion of U.S. lettuce production does come from hot, arid regions like Yuma and the Salinas Valley alone produce the majority of America's leafy greens. So those high water usage numbers aren't edge cases; they're industry norms.

Supporting Research

The Arizona State study isn't an outlier. Multiple peer-reviewed sources confirm similar water savings:

•      PMC Hydroponics Review (2023): "Hydroponic farming techniques have been found to reduce water usage by up to 90% compared to conventional soil-based farming."

•      ScienceDirect (2022): "Through hydroponic farming system we can assure minimum water savings of up to 70-80% compared to soil-based farming system."

•      ResearchGate Comparative Study: Found hydroponic spinach cultivation used 97.42% less water than conventional methods over 21 days.

The Bottom Line

The 90%+ water savings is documented across multiple peer-reviewed studies from respected institutions including Arizona State University, MIT Terrascope, and international agricultural research journals.

Yes, hydroponic systems require maintenance like flushing. Yes, some evaporation still occurs. No, these factors don't meaningfully change the water efficiency advantage. The math isn't even close.

At Grow Space, we're proud to grow chemical-free lettuce and microgreens right here in Kenosha using a fraction of the water that conventional farming requires. 

Sources

6.    Barbosa, G.L. et al. (2015). "Comparison of Land, Water, and Energy Requirements of Lettuce Grown Using Hydroponic vs. Conventional Agricultural Methods." International Journal of Environmental Research and Public Health, 12(6), 6879-6891. https://pmc.ncbi.nlm.nih.gov/articles/PMC4483736/

7.    "Hydroponics: Current Trends in Sustainable Crop Production." (2023). PMC / National Institutes of Health. https://pmc.ncbi.nlm.nih.gov/articles/PMC10625363/

8.    "Hydroponic Farming – A State of Art for the Future Agriculture." (2022). ScienceDirect / Materials Today: Proceedings. https://www.sciencedirect.com/science/article/abs/pii/S2214785322056048

9.    Pomoni, D.I. et al. (2023). "A Review of Hydroponics and Conventional Agriculture Based on Energy and Water Consumption, Environmental Impact, and Land Use." Energies, 16(4). https://www.mdpi.com/1996-1073/16/4/1690

10. MIT Terrascope (2024). "Environmental Impact of Hydroponic Systems." https://terrascope2024.mit.edu/?page_id=315

—

Grow Space Vertical Farms