Aerial photo of a golf course in a hilly desert
Human activity, including the introduction of nonnative vegetation like this grassy golf course outside Las Vegas, Nev., influences the water cycle in ways not depicted in most water cycle diagrams, new research suggests. Credit: Pete McBride/National Geographic Image Collection/Getty Images

Quick—name a scientific diagram you studied as a grade-schooler.

A depiction of the water cycle probably tops that list. But now researchers have shown that the majority of familiar water cycle diagrams are flawed in fundamental ways. That’s bad news because students, educators, and policy makers alike often accept water cycle diagrams as accurately representing the movement of our planet’s most basic resource.

Where Are the People?

This investigation of water cycle diagrams started as an academic question over lunch one day, said Benjamin Abbott, an ecosystem ecologist at Brigham Young University in Provo, Utah. How are people thinking about the Earth’s big cycles like the water cycle, he and other researchers wondered? When Abbott and his colleagues started looking at a few water cycle diagrams, they realized something.

“It kind of dawned on us,” said Abbott. “People are missing from almost all of these.”

Abbott and his collaborators began systematically collecting water cycle diagrams. They did Internet image searches for terms such as “water cycle” and “hydro cycle,” among others, and pulled up 350 diagrams from 12 countries. The researchers also mined textbooks, scientific literature, and government-published documents, and recovered 114 English language diagrams of the water cycle.

In total, they amassed over 450 unique diagrams published as early as the 1940s.

The researchers then analyzed these depictions of water cycling through, on, and above the terrestrial Earth. They found that the vast majority of the diagrams—85%—failed to show any effect of humans on the water cycle.

That’s unfortunate and inaccurate, said Abbott, because people have had a pronounced impact on the water cycle. Humans have changed the distribution of vegetation, for example, he said. “That’s actually affecting the land-to-atmosphere flux of water and also what happens to precipitation after it falls.”

Visual Bias

Researchers found that many of the diagrams were biased because of how they visually presented water resources, said Abbott. For instance, groundwater was often shown as extending down to the bottom of the page.

“That’s kind of implying there’s unlimited groundwater,” Abbott said.

Over 95% of the water cycle diagrams showed temperate, forested regions despite most of the world’s population living in drier areas.

Finally, climate change and water pollution, both major contributors to water crises, were noted in only 2% of the diagrams.

“You’re missing all of these realities,” said Abbott. These results were published in Nature Geoscience.

A Few Suggestions

Water cycle diagrams can be improved in three ways: by portraying different types of biomes, by conveying temporal changes in water cycling in different seasons, and by showing humans interacting with water.

The scientists suggest that water cycle diagrams can be improved in three ways: by portraying different types of biomes, by conveying temporal changes in water cycling in different seasons, and by showing humans interacting with water.

“There’s no reason why we can’t integrate that into our water cycle diagrams, especially when we’re using animated or interactive diagrams,” said Abbott.

This is a unique study that melds human and physical aspects, said Paul Durack, an oceanographer at Lawrence Livermore National Laboratory in Livermore, Calif., not involved in the research. “How we communicate human influence and interference into the water cycle is something we could do a far better job of.”

Abbott and his colleagues are currently applying for funding to put together an open-source suite of static and interactive water cycle diagrams. They plan to work with teachers and hydrologists to produce diagrams that are accurate, visually appealing, and useful to audiences ranging from students to policy makers.

“We want to effectively communicate what’s going on with water and what we could be doing better to solve the global water crisis,” said Abbott.

—Katherine Kornei (@katherinekornei), Freelance Science Journalist


Kornei, K. (2019), Many water cycle diagrams promote misconceptions, Eos, 100, Published on 13 June 2019.

Text © 2019. The authors. CC BY-NC-ND 3.0
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