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.
Résumé
On pense que, à l’époque préhistorique, la population de Rapa Nui (île de Pâques) se comptait par milliers bien que les sources d’eau de boisson classiques (rivières, sources) aient été à peu près absentes sur l’île. Des témoignages des premiers explorateurs européens, on sait que les habitants de Rapa Nui utilisaient pour boire de l’eau saumâtre. Presque rien d’autre n’est. connu sur les ressources en eau dans la préhistoire. Cet article discute des études de terrain qui suggèrent que les anciens habitants de Rapa Nui ont survécu à des périodes de sècheresse grâce à leur utilisation des eaux souterraines saumâtres qui affleuraient abondamment le long des côtes. Cette eau était interceptée par des tranchées, possiblement recueillie dans des petits bassins ou juste récupérée à partir de la surface de l’eau de mer. Deux enquêtes de terrain ont permis d’identifier de nombreuses localisations d’eau saumâtre mais potable le long de la côte. Ces enquêtes n’ont pas permis d’identifier des sources à l’intérieur des terres qui seraient de possibles sources d’eau résistant à la sécheresse. Même si les sources d’eau souterraine côtière sont de faible qualité, elles ont été un apport apparemment suffisant pour les habitants et leur ont permis de construire les superbes statues (moai) qui ont rendu fameuse l’île de Pâques.
Resumen
Se cree que la población de Rapa Nui (Isla de Pascua) en tiempos prehistóricos se ha contado por miles, aunque las fuentes perennes típicas de agua potable (arroyos, manantiales) están casi ausentes en la isla. Según los relatos de los primeros exploradores europeos, se sabe que la gente de Rapa Nui utilizaba agua potable salobre. Más allá de esto, casi no se sabe nada de los recursos hídricos en la prehistoria. Este artículo informa sobre estudios de campo que sugieren que los antiguos habitantes de Rapa Nui sobrevivieron a períodos de sequía debido a la utilización de descargas de aguas subterráneas salobres que emergen de manera flotante en las costas. Esta agua fue colocada en trincheras de intercepción, posiblemente capturadas en embalses costeros, o simplemente filtrada de la superficie del agua de mar. Dos estudios de campo indican abundantes ubicaciones de agua salobre pero potable a lo largo de la costa. Los relevamientos de campo no identificaron fuentes situadas tierra adentro que probablemente sean fuentes de agua resistentes a la sequía. Aunque las fuentes costeras de agua subterránea son de baja calidad, aparentemente fueron suficientes para mantener a la población y permitirles construir las magníficas estatuas (moai) por las que es famosa la Isla de Pascua.
摘要
史前时期Rapa Nui(复活节岛)的人口数量通常认为达几千人,尽管岛上几乎不存在典型的四季不断的饮用水资源(河流、泉)。从欧洲早期探险者的记录得知,Rapa Nui的居民用微咸水当做饮用水。除此之外,人们几乎对史前的水资源一无所知。本文论述了野外研究成果,研究成果表明Rapa Nui古代居民在干旱期利用从地下排泄出的、漂浮在海岸线的微咸地下水维持生命。这种水在拦截沟壕汇集成池塘,可能是在沿海蓄水中被截留或者从海水面上被撇留。两次野外调查表明,沿海岸线有大量的微咸但可以饮用的水储存地。野外调查未能确定可能是抗旱水源的分散内陆水源。尽管沿海地下水源水质很差,但很明显足够维持这些人口的生命以及使他们能够建造使复活岛名声鹊起的雄伟雕像(摩埃)。
Resumo
Acredita-se que a população de Rapa Nui (Ilha de Páscoa) no tempo pré-histórico era numerosa aos milhares embora fontes perenes típicas de água potável (rios, nascentes) sejam quase ausentes na ilha. Pelas contas dos primeiros exploradores europeus, sabe-se que o povo de Rapa Nui utilizava água salobra para consumo. Além disso, quase nada é conhecido dos recursos hídricos na pré-história. Esse trabalho reporta-se à estudos de campo que sugerem que os antigos habitantes de Rapa Nui sobreviveram a períodos de seca por causa da utilização de descarga de águas subterrâneas salobras que rompe em superfície flutuante nas linhas costeiras. Essa água foi empoçada em trincheiras de interceptação, possivelmente capturada em represamentos costeiros, ou apenas criando uma fina camada na superfície da água salgada. Duas pesquisas de campo indicam locais de água salobra e potável abundante pela linha costeira. As pesquisas de campo falharam em identificar os recursos distribuídos em para dentro da ilha que são as prováveis fontes de água resistentes à seca. Embora as fontes de águas subterrâneas costeiras sejam de baixa qualidade, elas eram aparentemente suficientes para suprir a população e permitir que eles construíssem estátuas magníficas (moai) pelas quais a Ilha da Páscoa é famosa.
Özet
Adada neredeyse hiç tipik uzun ömürlü içme suyu kaynağı (akarsular, membalar) bulunmamasına rağmen, Rapa Nui’nin (Paskalya Adası) tarihöncesi çağlardaki nüfusunun binler düzeyinde olduğu düşünülmektedir. İlk Avrupalı kaşiflerin kayıtlarına göre Rapa Nui halkının tuzlu su tükettiği bilinmektedir. Bunun dışında, tarihöncesi su kaynakları ile ilgili neredeyse hiçbir şey bilinmemektedir. Bu araştırmanın saha çalışmalarına göre Rapa Nui’nin geçmişteki sakinleri, sahil şeridinde su yüzüne çıkan hafif tuzlu yeraltı suyu boşalımından faydalanarak kuraklık dönemleri atlatmıştır. Bu su, hendeklerde depolanmış, muhtemelen kıyısal barajlarda yakalanmış, veya yalnızca deniz suyunun yüzeyinden sıyrılmıştır. İki saha çalışması, sahil şeridi boyunca pek çok noktada tuzlu ancak içilebilir su bulunduğunu ortaya koymuştur. Saha çalışmaları, yayılmış halde bulunan ve kuraklığa direnebilecek karasal su kaynaklarının tespit edilmesinde başarısız olmuştur. Kıyısal yeraltı suyu kaynakları düşük kaliteli olmalarına rağmen, görünüşe göre halkın ihtiyacını gidermeye ve Paskalya Adası’nın meşhur görkemli heykellerini (moai) inşa etmeye yetecek seviyedeydi.
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Acknowledgements
The authors would like to thank Michelle Baroldi and Matthew Cole for their assistance in the field, and Comunidad Indigena Ma‘u Henua, the Consejo de Monumentos Rapa Nui, Consejo de Monumentos Chile, CONAF, COEIPA, and the people of Rapa Nui for allowing us to work on their island. We also thank Hetereki Huke for his guidance and support without which this research would not be possible.
Funding
The fieldwork was supported by NSF Award No. 1005258 “Geospatial Research and Mapping on Easter Island” (Co-PIs: Christopher Lee, California State University Long Beach, Carl Lipo, Binghamton University and Terry Hunt, University of Arizona) and the Bert and Ethel Conrey Endowed Chair in Hydrogeology.
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Brosnan, T., Becker, M.W. & Lipo, C.P. Coastal groundwater discharge and the ancient inhabitants of Rapa Nui (Easter Island), Chile. Hydrogeol J 27, 519–534 (2019). https://doi.org/10.1007/s10040-018-1870-7
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DOI: https://doi.org/10.1007/s10040-018-1870-7