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martyb writes:

Easter Island Inhabitants Collected Freshwater from the Ocean's Edge in Order to Survive:

Ancient inhabitants of Rapa Nui (Easter Island) maintained a society of thousands by utilizing coastal groundwater discharge as their main source of "freshwater," according to new research from a team of archaeologists including faculty at Binghamton University, State University at New York.

The team, which included Binghamton University Professor of Anthropology Carl Lipo, measured the salinity of coastal water around the island of Rapa Nui, in order to determine whether or not the water close to the shores had a salt concentration low enough for humans to safely drink.

The process of coastal groundwater discharge makes it possible for humans to collect drinkable freshwater directly where it emerges at the coast of the island.

By measuring the percentage of salt in the coastal waters, and finding it safe for human consumption, and by eliminating other options as primary sources of drinking water, the researchers concluded that groundwater discharge was a critical factor in the sustenance of the large population the island is thought to have harbored.

"The porous volcanic soils quickly absorb rain, resulting in a lack of streams and rivers," Lipo said. "Fortunately, water beneath the ground flows downhill and ultimately exits the ground directly at the point at which the porous subterranean rock meets the ocean. When tides are low, this results in the flow of freshwater directly into the sea. Humans can thus take advantage of these sources of freshwater by capturing the water at these points."

Lipo said the freshwater mixes with the saltwater slightly, creating what's called brackish water, but not enough for the water to contain harmful levels of salt to human consumers. It does, however, mean that the islanders rarely used salt on their foods, because the water they drank contributed so drastically to their daily salt intake.

I wonder how the inhabitants found out where and when it was safe to drink the water?

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