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The ancient inhabitants of Rapa Nui (Easter Island) have maintained a society of several thousand people using the coastal groundwater discharge as the main source of fresh water, according to a new study by a team of # 39; archaeologists including professors from the University of Binghamton and the State University of New York.
The team, which included Carl Lipo, Professor of Anthropology at Binghamton University, measured the salinity of coastal waters around Rapa Nui Island to determine if the salt concentration in the water near ribs was low enough for the man to drink safely. .
The process of evacuating coastal groundwater allows humans to collect fresh drinking water directly to the place where it emerges on the coast of the island.
By measuring the percentage of salt in coastal waters, finding it safe for human consumption and eliminating other options as primary sources of drinking water, the researchers concluded that groundwater discharge was an essential factor in the livelihood of the island's large population is believed to have housed.
"Porous volcanic soils quickly absorb rain, resulting in a lack of streams and rivers," said Lipo. "Fortunately, groundwater flows downhill and eventually comes out of the ground directly to the point where porous underground rock meets the ocean. When the tides are low, it causes a flow of fresh water directly into the sea. Humans can thus take advantage of these freshwater sources by capturing water at these points. "
Lipo explained that freshwater mixed slightly with salt water, creating so-called brackish water, but not enough for the water to contain harmful levels of salt for consumers. This means, however, that islanders rarely used salt for their food because the water they drank contributed so much to their daily salt intake.
Lipo's team said the researchers had often wondered why the island's famous statues were found only in certain places around the island, with a high concentration of them near the coast.
"Now that we know more about the location of fresh water, however, the location of these monuments and other elements makes sense: they are placed where the Fresh water is immediately available, "said Lipo.
He said that there were very few freshwater sources on the island, including two extremely difficult lakes, no creeks and a source often reduced to a wet peat bog. . Much of the opposition to the Lipo team's research is the presence of taheta on the island, which are small cut cisterns used for collecting precipitation. To refute this argument, the Lipo team explained that if collecting rainwater was essential for the survival of the islands, the cisterns would be much larger, instead of being able to contain only two to four liters of water each.
The team's research shows that the little precipitation received by Rapa Nui (1240 mm / year), associated with the basic evaporation rate of water in a climate such as that of the 39, island, means that on average, taheta can not be used as a viable source of drinking water 317 days of the year.
This led the researchers to conclude that there must be a different source of drinking water for a population of several thousand individuals to be able to support themselves. European accounts of early encounters with the island in the 18th century include passages where the natives seem to simply drink seawater. Since the human body can not handle the high salt concentration of the sea sea water, this supports the team's theory of groundwater discharge.
Lipo said the next project of the group was to try to understand how the availability of freshwater in some places was closely related to the methods and means used to build the large statues of the island. He hopes this research will benefit both science and the modern world.
"This information has finally shed light on the conditions that have governed and allowed these communities to work together to achieve their engineering achievements," said Lipo. "By gaining knowledge about community-wide behaviors, we can better understand the general conditions for group-level cooperation, whether in the past or in contemporary society."
The article entitled "Coastal Groundwater Discharge and the Former inhabitants of Rapa Nui, Chile (Easter Island)" was published in Journal of Hydrogeology.
More information:
Tanya Brosnan et al, Coastal Groundwater Discharge and the ancient inhabitants of Rapa Nui (Easter Island), Chile, Journal of Hydrogeology (2018). DOI: 10.1007 / s10040-018-1870-7
The ancient inhabitants of Rapa Nui (Easter Island) have maintained a society of several thousand people using the coastal groundwater discharge as the main source of fresh water, according to a new study by a team of # 39; archaeologists including professors from the University of Binghamton and the State University of New York.
The team, which included Carl Lipo, Professor of Anthropology at Binghamton University, measured the salinity of coastal waters around Rapa Nui Island to determine if the salt concentration in the water near ribs was low enough for the man to drink safely. .
The process of evacuating coastal groundwater allows humans to collect fresh drinking water directly to the place where it emerges on the coast of the island.
By measuring the percentage of salt in coastal waters, finding it safe for human consumption and eliminating other options as primary sources of drinking water, the researchers concluded that groundwater discharge was an essential factor in the livelihood of the island's large population is believed to have housed.
"Porous volcanic soils quickly absorb rain, resulting in a lack of streams and rivers," said Lipo. "Fortunately, groundwater flows downhill and eventually comes out of the ground directly to the point where porous underground rock meets the ocean. When the tides are low, it causes a flow of fresh water directly into the sea. Humans can thus take advantage of these freshwater sources by capturing water at these points. "
Lipo explained that freshwater mixed slightly with salt water, creating so-called brackish water, but not enough for the water to contain harmful levels of salt for consumers. This means, however, that islanders rarely used salt for their food because the water they drank contributed so much to their daily salt intake.
Lipo's team said the researchers had often wondered why the island's famous statues were found only in certain places around the island, with a high concentration of them near the coast.
"Now that we know more about the location of fresh water, however, the location of these monuments and other elements makes sense: they are placed where the Fresh water is immediately available, "said Lipo.
He said that there were very few freshwater sources on the island, including two extremely difficult lakes, no creeks and a source often reduced to a wet peat bog. . Much of the opposition to the Lipo team's research is the presence of taheta on the island, which are small carved cisterns used for collecting precipitation. To refute this argument, the Lipo team explained that if collecting rainwater was essential for the survival of the islands, the cisterns would be much larger, instead of being able to contain only two to four liters of water each.
The team's research shows that the little precipitation received by Rapa Nui (1240 mm / year), associated with the basic evaporation rate of water in a climate such as that of the 39, island, means that on average, taheta can not be used as a viable source of drinking water 317 days of the year.
This led the researchers to conclude that there must be a different source of drinking water for a population of several thousand individuals to be able to support themselves. European accounts of early encounters with the island in the 18th century include passages where the natives seem to simply drink seawater. Since the human body can not handle the high salt concentration of the sea sea water, this supports the team's theory of groundwater discharge.
Lipo said the next project of the group was to try to understand how the availability of freshwater in some places was closely related to the methods and means used to build the large statues of the island. He hopes this research will benefit both science and the modern world.
"This information has finally shed light on the conditions that have governed and allowed these communities to work together to achieve their engineering achievements," said Lipo. "By gaining knowledge about community-wide behaviors, we can better understand the general conditions for group-level cooperation, whether in the past or in contemporary society."
The article entitled "Coastal Groundwater Discharge and the Former inhabitants of Rapa Nui, Chile (Easter Island)" was published in Journal of Hydrogeology.
More information:
Tanya Brosnan et al, Coastal Groundwater Discharge and the ancient inhabitants of Rapa Nui (Easter Island), Chile, Journal of Hydrogeology (2018). DOI: 10.1007 / s10040-018-1870-7
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