New diagrams explain how humans affect water cycle

Representations of the Earth's water cycle used in textbooks throughout the world need to be updated, say scientists who have drawn up a new set of diagrams to include effects of human interference. Leaving humans out of the picture contributes to a basic lack of awareness of how humans relate to water on Earth -- and a false sense of security about future availability of this essential and scarce resource, according to the study published in the journal Nature Geoscience.

The team from the University of Birmingham in the UK, Brigham Young University and Michigan State University in the US has drawn up a new set of diagrams to promote a better understanding of how our water cycle works in the 21st century. These new diagrams show human interference in nearly all parts of the cycle.

In a sample of more than 450 water cycle diagrams in textbooks, scientific literature and online, 85 per cent showed no human interaction at all with the water cycle, and only two per cent of the images made any attempt to connect the cycle with climate change or water pollution. In addition, nearly all the examples studied depicted verdant landscapes, with mild climates and abundant freshwater -- usually with only a single river basin.

The researchers argue there is an urgent need to challenge this misrepresentation and promote a more accurate and sophisticated understanding of the cycle and how it works in the 21st century. This is crucial if society is to be able to achieve global solutions to the world's water crisis.

"The water cycle diagram is a central icon of hydroscience, but misrepresenting the ways in which humans have influenced this cycle diminishes our awareness of the looming global water crisis," said David Hannah, UNESCO Chair in Water Sciences at the University of Birmingham. "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," said Hannah.

The new diagrams drawn up by the team show a more complex picture that includes elements such as meltwater from glaciers, flood damage caused by land use changes, pollution and sea level rises. "Every scientific diagram involves compromises and distortions, but what we found with the water cycle was the widespread exclusion of a central concept. You can't understand water in the 21st century without including humans," said Ben Abbott, from Brigham Young University.

"Other scientific disciplines have done a good job depicting how humans now dominate many aspects of the Earth system. It's hard to find a diagram of the carbon or nitrogen cycle that doesn't show factories and fertilisers," said Abbott. "However, our drawings of the water cycle are stuck in the 17th century," he said.

"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," he added.

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