Map App Could Aid Global Surface Water Management

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By Stephen Gardner

Dec. 12 — Surface waters roughly equivalent to the area of Lake Superior have disappeared in the last three decades because of human intervention and environmental change, with the loss concentrated in the Middle East and Central Asia, according to an online global mapping application launched Dec. 12.

But overall, river damming and—to a lesser degree—climate change have led to a net increase in surface water across the globe, according to the Global Surface Water Explorer, which the European Union and Google Earth Engine have developed.

The online application is built on 32 years’ worth of satellite data. Users can click at any part of the world map to obtain a record of whether surface water coverage at that point has increased, decreased or stayed the same.

The European Commission, the EU’s executive, said 90,000 square kilometers worldwide that were previously covered by lakes, wetlands and rivers are now dry, and an additional 72,000 square kilometers of previously permanent surface water is now present only seasonally. These losses must be compared against gains of about 213,000 square kilometers, meaning a net gain of about 52,000 square kilometers.

Hard-Hit Areas

The commission said surface water losses could be attributed to factors such as climate change, drought and unregulated water use, and are heavily concentrated in Afghanistan, Iraq, Iran, Kazakhstan and Uzbekistan, where 70 percent of the losses have occurred.

In the U.S., the commission said, “A combination of drought and sustained demands for water have led to a loss of 33 percent of surface water in Arizona, California, Idaho, Nevada, Oregon and Utah.”

Gains in surface water area are more evenly distributed than losses and are primarily a consequence of river damming, though “accelerated snow and glacier melt caused by higher temperatures and increased rainfall” also have played a part, according to the commission.

The Global Surface Water Explorer is free to access and could help policy makers “better design and monitor measures to prevent and mitigate the amount of flooding, water scarcity and droughts,” the commission said.

To contact the reporter on this story: Stephen Gardner in Brussels at

To contact the editor responsible for this story: Greg Henderson at

For More Information

The Global Surface Water Explorer is available at

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