Water securityGlobal freshwater loss due to dams, irrigation much larger than previously thought
Dams and irrigation, by increasing evapotranspiration, raise the global human consumption of freshwater to a much higher level than previously thought. This effect increases the loss of freshwater to the atmosphere and thereby reduces the water available for humans, societies and ecosystems on land.
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Dams and irrigation raise the global human consumption of freshwater to a much higher level than previously thought, according to research from Stockholm University. The results are published in the scientific journal Science.
The new study shows that dams and irrigation considerably raise the global human consumption of freshwater by increasing evapotranspiration. This effect increases the loss of freshwater to the atmosphere and thereby reduces the water available for humans, societies and ecosystems on land.
“Small things that we do on the surface of the Earth can have large global effects. Previously, the global effects of local human activities such as dams had been underestimated. This study shows that, so far, the effects are even greater than those from atmospheric climate change”, says Fernando Jaramillo, postdoc at the Department of Physical Geography at Stockholm University.
Hundred years of data
Stockholm U reports that the researchers have compiled and analyzed data from 1901 to 2008 for climate, hydrology, and water use in one hundred large hydrological basins spread over the world. Their results raise the previous estimate of the global human freshwater footprint by almost 20 percent. The increase in total freshwater loss from the landscape to the atmosphere is calculated to be 4,370 km3 per year. This corresponds to two thirds of the annual flow of the Amazon River, the world’s largest river by discharge.
“The human-caused increase in this loss is like a huge river of freshwater from the landscape to the atmosphere. We have changed so much of the freshwater system without knowing it. Our study shows that we have already passed a proposed planetary boundary for freshwater consumption. This is serious, regardless of whether we have crossed a real boundary or if the boundary has been underestimated”, says Gia Destouni, Professor at Stockholm University.
— Read more in F.Jaramillo and G. Destouni, “Local flow regulation and irrigation raise global human water consumption and footprint,” Science 350 no. 6265 (4 December 2015): 1248-51 (DOI:10.1126/science.aad1010)
