Coastal groundwater discharge and the ancient inhabitants of Rapa Nui (Easter Island), Chile

Abstract

The population of Rapa Nui (Easter Island) in pre-historic time is believed to have numbered in the thousands although typical perennial sources of drinking water (streams, springs) are nearly absent from the island. From the accounts of early European explorers, it is known that the people of Rapa Nui utilized brackish drinking water. Beyond this, almost nothing is known of the water resources in prehistory. The authors report here on field studies that suggest the ancient inhabitants of Rapa Nui survived periods of drought due to their utilization of brackish groundwater discharge that surfaces buoyantly at coastlines. This water was ponded in interception trenches, possibly captured in coastal impoundments, or just skimmed from the surface of seawater. Two field surveys indicate abundant locations of brackish but potable water along the coastline. The field surveys failed to identify distributed inland sources that are likely drought-resistant sources of water. Although coastal groundwater sources of are of poor quality, they were apparently sufficient to support the population and allow them to build the magnificent statues (moai) for which Easter Island is famous.