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from the whatever-you-do,do-NOT-ask-for-help-from-Montezuma dept.
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?
(Score: 5, Informative) by JoeMerchant on Friday October 12 2018, @04:12PM
Like the Anasazi who preferred round bowls over square ones - you notice that more people die after eating from square bowls (because the crevices harbor bacteria, but they didn't need to know that part.) As for salt in the water - once you know, that's something you should be able to tell by taste, most of the time.
Florida used to work this way, too... rainwater on the peninsula and islands would create a freshwater "lens" that actually extended out into the sea some distance. When my dad was a kid (early 50s), you could dig a shallow hole (less than 3' deep) almost anywhere and get fresh, drinkable water.
Power pumping of groundwater meant that by the 1980s, shallow wells had to go down 15' or more, well below the "hardpan" layer that used to mark the seasonal high groundwater mark, hardpan is iron oxide - rust and it accumulated in a layer an inch or so thick, usually just a foot or two below the surface, throughout much of central Florida.
Today, due to continued groundwater pumping, salt water from the coasts has intruded miles inland in places, sickening deep rooted trees that aren't salt resistant - and didn't need to be because the land they were growing on had been salt free for thousands to millions of years. Shallow wells are too salty to water most grass with along much of the coast now.
Of course, that's better than the Houston area where groundwater pumping has led to a phenomenon called subsidence: the land literally sinks into Galveston bay when the water is removed from underneath it. Our house there started at 30' above sea level in the 1960s and was down to 19' before they got the pumping under control in that area. Some neighborhoods have been completely condemned because they've sunk so low that they flood on an ordinary high tide.
As for Rapa Nui - it's still pretty sparse, populationwise, they should be in good shape for natural rainwater collection more than meeting their fresh drinking water needs. Of course, today they can sink wells - if they're smart they won't put the well casings down below sea level so that they suck air before they start saltwater intruding their natural source of drinking water.
Україна досі не є частиною Росії Слава Україні🌻 https://www.pravda.com.ua/eng/news/2023/06/24/7408365/