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Scientists have created high resolution maps of points around the world where the water table meets the oceans – the first of this type of analysis of this type likely to contribute to the protection of drinking water and the seas .
In a study published in the journal Letters of geophysical research, Researchers at Ohio State University in the United States have shown that nearly half of the fresh groundwater flows into the ocean near the tropics.
They also found that areas near active fault lines send larger volumes of groundwater into the ocean than tectonically stable regions.
They found that dry, arid regions caused very little groundwater discharge, opening up the limited groundwater reserves in these parts of the world to saltwater intrusion.
The team worked with researchers at NASA's Jet Propulsion Laboratory and the University of Saskatchewan to combine topographic data from satellites and climate models to show the flow of groundwater along the world's coasts. .
Manage freshwater
The results could help coastal communities better protect and manage their drinking water.
"Freshwater and groundwater discharges constitute a natural line of defense against saltwater intrusion," said Audrey Sawyer, assistant professor at the Ohio State.
"It's a problem that the drylands produce so little groundwater, because these are also the places where people will tend to look for groundwater to meet their freshwater needs," the report said. Dr. Sawyer.
The research, the first near-global, high-resolution, spatially distributed map of soft groundwater flow towards the coast, could provide scientists with better clues about groundwater discharge control points.
When researchers look at the quality of coastal water and how it affects the biochemical composition of the world's lakes and oceans, they usually think of rivers and streams for good reason . Most of the water that goes to lakes and oceans comes from surface water sources. However, groundwater also plays an important role in transporting minerals and, in some cases, pollutants to surface water bodies.
"If you've ever swam in a lake or in the ocean in the summer and you're going through an area of cold, it's probably a place where groundwater escapes," said Dr. Sawyer.
"And this is only one of the ways in which groundwater affects surface water: in this case, it affects the temperature but also the chemistry of the water. These effects can be difficult to measure on a large scale, "he said.
The team started to build these images. The research group focused on groundwater and realized that there was little information indicating where groundwater was most likely to dump into the oceans .
The study found that in some parts of the world, groundwater could pollute oceans and lakes with nutrients and other chemicals.
Groundwater, for example, may contain higher concentrations of nitrates – a determining factor in the types of harmful algal blooms – as well as high concentrations of mercury.
Understanding how and where groundwater reaches surface water could help decision makers develop better plans to improve these water bodies.
The study also revealed that climate has a strong influence on groundwater flow and that cities located in dry areas are particularly vulnerable to contamination of aquifers by salt water.
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