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首页> 外文期刊>Science of the total environment >Groundwater flow in a relatively old oceanic volcanic island: The Betancuria area, Fuerteventura Island, Canary Islands, Spain
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Groundwater flow in a relatively old oceanic volcanic island: The Betancuria area, Fuerteventura Island, Canary Islands, Spain

机译：相对古老的海洋火山岛中的地下水流：西班牙加那利群岛富埃特文图拉岛Betancuria地区

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The island of Fuerteventura is the oldest of the Canary Islands' volcanic archipelago. It is constituted by volcanic submarine and subaerial activity and intrusive Miocene events, with some residual later volcanism and Quaternary volcanic deposits that have favored groundwater recharge. The climate is arid, with an average rainfall that barely attains 60 mm/year in the coast and up to 200 mm/year in the highlands. The aquifer recharge is small but significant; it is brackish due to large airborne atmospheric salinity, between 7 and 15 g m~(-2) year~(-1) of chloride deposition, and high evapo-concentration in the soil. The average recharge is estimated to be less than about 5 mm/year at low altitude and up to 10 mm/year in the highlands, and up to 20 mm/year associated to recent lava fields. Hydrochemical and water isotopic studies, supported by water table data and well and borehole descriptions, contribute a preliminary conceptual model of groundwater flow and water origin in the Betancuria area, the central area of the island. In general, water from springs and shallow wells tends to be naturally brackish and of recent origin. Deep saline groundwater is found and is explained as remnants of very old marine water trapped in isolated features in the very low permeability intrusive rocks. Preliminary radiocarbon dating indicates that this deep groundwater has an apparent age of less than 5000 years BP but it is the result of mixing recent water recharge with very old deep groundwater. Most of the groundwater flow occurs through the old raised volcanic shield of submarine and subaerial formations and later Miocene subaerial basalts. Groundwater transit time through the unsaturated zone is of a few decades, which allows the consideration of long-term quasi-steady state recharge. Transit times are up to a few centuries through the saturated old volcanics and up to several millennia in the intrusive formations, where isolated pockets of very old water may exist.
机译：富埃特文图拉岛是加那利群岛最古老的火山群岛。它由火山的海底和地下活动以及侵入性的中新世事件构成，一些残留的后期火山岩和第四纪火山沉积有利于地下水补给。气候是干旱的，沿海地区的平均降雨量几乎只有60毫米/年，而高地地区则高达200毫米/年。含水层的补给量很小但很大；由于大气中的高盐度，7至15 g m〜（-2）年〜（-1）的氯化物沉积以及土壤中的高蒸发浓度，因此微咸。在低海拔地区，平均补给量估计小于每年约5毫米，在高地地区，平均补给量为每年10毫米，与最近的熔岩田相关的平均补给量为每年20毫米。在地下水位数据以及井眼和井眼描述的支持下进行的水化学和水同位素研究，为该岛中心地区贝坦库里亚地区的地下水流量和水源提供了初步的概念模型。通常，来自泉水和浅井的水往往是天然微咸的，并且是最近才有的。发现了深层盐水，并将其解释为非常老的海水残留在非常低渗透率的侵入性岩石中的孤立特征中。初步放射性碳测年表明，该深层地下水的表观年龄小于5000年BP，但这是最近的补给水与非常老的深层地下水混合的结果。大部分地下水流是通过旧的海底和空中构造的凸起火山护层以及后来的中新世的地下玄武岩产生的。地下水通过非饱和区的时间为几十年，这可以考虑长期准稳态补给。穿越饱和的旧火山的运输时间长达数个世纪，而侵入性地层中可能存在孤立的非常老的水域，其穿越时间长达数千年。

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