In 2024, a Dutch sports field stored rainwater beneath artificial turf, cutting surface temperatures by nearly 50% during summer tests

Anyone who has jogged across a synthetic football pitch on a summer afternoon knows how hot it can feel underfoot. Now there's hard data to back up that discomfort, and a possible fix for it. Researchers report in a study titled 'Climate adaptive solution for artificial turf in cities: integrated rainwater storage and evaporative cooling,' published in Frontiers in Sustainable Cities in 2024, that they built a sports field in Amsterdam with a hidden layer beneath the artificial turf that stores rainwater. That stored water rises and evaporates when the sun heats the surface and takes the heat away. On June 25, 2020, near the middle of a warm spell during the field test, the treated turf reached 37 degrees Celsius while a nearby standard artificial pitch reached 62.5 degrees Celsius, a difference of more than 25 degrees.

A hidden tank under the grass

The study was led by hydrologist Marjolein van Huijgevoort of KWR Water Research Institute, working with Wageningen University. Its principle is simple and borrowed from green roofs: beneath the turf is a shallow water-storage layer, about 8.5 centimeters deep, with small columns filled with absorbent rockwool fibers. Instead of running straight into city drains, this hidden reservoir soaks up the rain. As the turf warms, the columns draw water up by capillary action, like a paper towel drawing up a spill, and allow it to evaporate at the surface. There are no pumps and no electricity. It operates automatically in response to weather conditions.


The numbers behind the cooling

In the summer of 2020, the team tested four plots next to each other in Amsterdam: natural grass, normal artificial turf, and two versions of the self-cooling turf. The results were stark. On June 25, 2020, the regular artificial turf heated up to 62.5 degrees Celsius, while the cooled version only reached 37 degrees Celsius, about 1.7 degrees warmer than the natural grass plot next to it. During the summer's warmer spells, including a stretch in August that the Royal Netherlands Meteorological Institute classified as a heatwave, conventional turf reached surface temperatures as high as 67.7 degrees Celsius. The cooled turf also stayed significantly cooler at night, which was important because the researchers linked steady nighttime warmth from ordinary turf to the larger urban heat island effect, the well-documented phenomenon in which cities trap more heat than the countryside around them, a pattern the Environmental Protection Agency has also documented.

Why turf heat is a real health concern

This is not just a matter of comfort. Sun-baked artificial turf has been linked to burns, rashes, and heat exhaustion, particularly in children and young athletes playing close to the ground. A 2017 study by researcher C.Y. Jim, titled 'Intense summer heat fluxes in artificial turf harm people and environment,' published in Landscape and Urban Planning, found that intense summer heat fluxes from artificial turf can pose real health risks for people playing on it. That risk increases as cities move to durable synthetic pitches instead of grass for heavier use. The Dutch pilot offers a way to keep the benefits of artificial turf, without the punishing heat that normally comes with it.

The catch: It all depends on water

The cooling effect only works because water continues to evaporate from below the surface. During this particular test summer, rainfall was sufficient to keep the underground layer topped up on its own, and the researchers note the system needed no manual refilling for the full three-month period, even through the August heatwave. The cooled plots stored and reused most of the rain that fell on them that summer, 83.8% at one plot, 69.6% at the other. The researchers caution that in drier areas or during longer dry spells than this one, the system would likely need supplemental irrigation to keep working, much like a normal lawn needs water in a drought. Another consideration is that the system costs more to install than traditional turf, which is why the researchers say cities will need a proper cost-benefit study before rolling it out widely. Cooling turf is not a one-time improvement. It is a small piece of water infrastructure that needs a steady water supply to keep working.

What this means for city planners, and for us

The researchers suggest the approach could offer young adults playing weekend five-a-side, or parents sending children to play on a synthetic pitch, a quieter, low-tech kind of climate adaptation. Instead of searching for exotic new materials, the answer might be as old as a rain barrel: catch water where it falls, and let it do the cooling work it always did for natural grass. Researchers now want to see the design tested in more field trials in different climates and where rainfall is less predictable. If those trials hold up, they suggest city parks departments could eventually have a useful tool for keeping outdoor sport cooler as summers get hotter.