Satellite Images Reveal How The Earth's Surface Water Has Changed

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Satellite Images Reveal How The Earth's Surface Water Has Changed

Using more than three million satellite images, researchers have mapped surface water around the world in stunning detail.

The high-resolution maps reveal how both natural processes and human activity have dramatically altered the global water distribution in just 32 years.

Since 1984, Earth’s surface has lost almost 90,000 square kilometers of water – an area roughly equivalent to that of Lake Superior – but it has also gained permanent water in almost all continental regions.

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Using more than three million satellite images, researchers have mapped surface water around the world in stunning detail. This map shows the River Ob in western Siberia, Russia. Dark blue colours are areas of permanent water, while and lighter blue colours indicates seasonal water. Green represents new areas of seasonal water, pink shows areas of lost seasonal water

These changes are primarily driven by drought, reservoir creation, and water extraction, the researchers explain in the study, published to the journal Nature.

In the exhaustive new effort, led by Jean-François Pekel of the European Commission, Joint Research Centre and colleagues, the team analyzed more than three million Landsat images taken between 1984 and 2015.

While scientists have previously attempted to map the global distribution of surface waters, they’ve struggled to measure the long-term changes at high-resolution.

But, the team was able to quantify month-to-month changes in surface water with staggering precision, at a resolution of 30 meters, using an algorithm to classify each 30m x 30m square as either land or open water.

This included both fresh and saltwater, while oceans were excluded.

According to the researchers, they noted the months and years when water was present, along with the seasonal and persistent changes.

The analysis revealed new insight on the effects of human activity on the planet.

When it comes to surface water losses, the researchers found that affected areas were more geographically concentrated than those that experienced gains.

Of the 90,000 square kilometers that have disappeared from the global surface, more than 70 percent of occurred in the Middle East and Central Asia.

The researchers have linked this to drought and human activity, including river diversion or damming, and unregulated withdrawal.

Long-term droughts also played a role in the losses seen in Australia and the US, they explain.

At the same time, new permanent bodies of surface water covering 184,000 square kilometers formed between 1984 and 2015.

The team noted that all continental regions experienced a net increase in permanent water, with the exception of Oceania, which had a net loss of one percent.

This, they say, is largely the result of reservoir filling, though ‘climate change is also implicated.’

The study now stands as the first global and methodologically consistent qualification of long-term surface water changes, and can help scientists to better understand the processes that effect it.

‘This globally consistent, validated data set shows that impacts of climate change and climate oscillations on surface water occurrence can be measured,’ the authors wrote, ‘and that evidence can be gathered to show how surface water is altered by human activities.’

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The Paraná River in North-Eastern Argentina is pictured, revealing how rivers meander and move, floodplains flood intermittently and new areas of permanent and seasonal water are being created and lost through time

See more photos: Daily Mail

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