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Here's why water cycle illustrations need humans in the picture

Remember those water cycle diagrams you studied in geography class? Among the green trees and blue seas, it turns out they’re missing an important factor: people.

Human water use, climate change and land conversion all have an impact on the water cycle but are rarely seen in the diagrams used in education and research throughout the world.

While critiquing these drawings might sound pedantic, a team of hydrology experts says the inaccuracies downplay the global water crisis and provide a false sense of security about how much water is available for us to use.

In an analysis of more than 460 water cycle diagrams found in textbooks, scientific literature and online, researchers found only 15% showed any human interaction with the water cycle. Just 2% made an attempt to connect the cycle with climate change or water pollution.

And nearly all the examples depicted green landscapes with mild climates and abundant freshwater, usually only with a single river basin.

The study, published in Nature Geoscience, was carried out by researchers from Brigham Young University and Michigan State University in the US and the University of Birmingham in the UK, along with partners in France, Canada, Switzerland and Sweden.

University of Birmingham UNESCO Chair in Water Sciences Professor David Hannah said the diagrams urgently need to be updated as they contribute to misunderstandings about global hydrology from policy makers, researchers and the public.

An updated diagram showing the human impact on the water cycle.

“The water cycle diagram is a central icon of hydro science, but misrepresenting the ways in which humans have influenced this cycle diminishes our awareness of the looming global water crisis,” Hannah said.

“By leaving out climate change, human consumption and changes in land use, we are in effect creating large gaps in understanding and perception among the public and also among some scientists.”

The researchers have drawn up a new diagram they say better reflects how the modern water cycle works. It paints a more complex picture that includes meltwater from glaciers, pollution, sea level rises, and flood damage caused by land-use changes.

While every scientific diagram involves compromises, Brigham Young Professor and study lead Ben Abbott said it is impossible to understand water in the 21st century without including human interference.

“Other scientific disciplines have done a good job depicting how humans now dominate many aspects of the Earth system,” Abbott said.

“It’s hard to find a diagram of the carbon cycle or the nitrogen cycle that doesn’t show factories and fertilisers. However, our drawings are stuck in the 17th century.

“Better drawings of the water cycle won’t solve the global water crisis on their own, but they could improve awareness of how local water use and climate change have global consequences.”