Hydrogeological settings of a volcanic island (San Cristóbal, Galapagos) from joint interpretation of airborne electromagnetics and geomorphological observations

Pryet, Alexandre; d’Ozouville, Noemí; Violette, Sophie; Deffontaines, Benoı̂t; Auken, Esben

doi:10.5194/hess-16-4571-2012

Cited by 26 publications

(13 citation statements)

References 50 publications

(54 reference statements)

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“…Owing to the thickness of the vadose zone, these circulations as well as inland aquifer geometries remain unclear, thereby increasing the complexity of groundwater access inland. Groundwater extraction is concentrated on the coastal edge (82% in Reunion Island; Join et al., 2005), where aquifers are vulnerable to saltwater intrusion (Oki et al., 1998; Pryet et al., 2012). In order to improve regional groundwater management, it is mandatory to improve the characterization of inland aquifers and include their possible impact on the recharge rates of basal aquifers.…”

Section: Introductionmentioning

confidence: 99%

“…Previous studies imaged different types of formation, saturation, or alteration degrees with the same range of resistivity. As an example, while d 'Ozouville et al (2008) interpreted 50-200 Ω•m as saturated basaltic flows in Santa Cruz Island (Galapagos), Pryet et al (2012), in San Cristobal Island, separated this threshold into two categories with either saturated (30-100 Ω•m) or weathered formations (100-400 Ω•m). These results show the need for a combined interpretation of resistivity data with geological, geophysical, and/ or groundwater measurements or observations.…”

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confidence: 99%

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Hydrogeophysical Characterization in a Volcanic Context From Local to Regional Scales Combining Airborne Electromagnetism and Magnetism

Dumont

Reninger

Aunay³

et al. 2021

Geophysical Research Letters

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In volcanic islands, a crucial step in managing watershed water resources is the characterization of groundwater aquifers from local to regional scales. Airborne geophysical data provide high‐resolution images down to hundreds of meters below the surface, over large areas. Yet, the production of an accurate interpretation of regional geophysical imagery may be time consuming or limited by the low density of geological and hydrological field observations. Here, we propose an approach combining airborne electromagnetic and magnetic data in order to reduce geophysical ambiguities and provide a multiscale hydrogeophysical characterization of Piton des Neiges volcano (Réunion Island). With limited calibration data, this methodology produces a geological model more accurate than using airborne electromagnetic data alone. Through the continuous coverage of both methods, we demonstrate the influence of volcanic unit geometries on groundwater flows within the critical zone and we highlight major structures impacting groundwater flows at both local and regional scales.

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Hydrogeophysical Characterization in a Volcanic Context From Local to Regional Scales Combining Airborne Electromagnetism and Magnetism

Dumont

Reninger

Aunay³

et al. 2021

Geophysical Research Letters

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“…Large spatial coverage can be obtained using airborne electromagnetic (AEM) methods. The SkyTEM system (Sørensen and Auken, 2004) is one of the available AEM methods that have been used extensively for groundwater mapping (Møller et al, 2009b;Pryet et al, 2012;Korus et al, 2017;Knight et al, 2018). By inverting the EM dataset a model of the electrical resistivity of the subsurface can be produced.…”

Section: Introductionmentioning

confidence: 99%

Combining Clustering Methods With MPS to Estimate Structural Uncertainty for Hydrological Models

et al. 2019

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“…Fig. 8A, springs resistivity analysis: 150-500 ohm m) and in comparison with other volcanic islands (d'Ozouville et al, 2008;Pryet et al, 2012;Vittecoq et al, 2014), it is assumed that these andesitic domes ( 9 αbi D ) are highly fissured and fractured, conferring a great hydraulic conductivity to this aquifer. Given the rooting of endogenous domes within the volcano, and as shown thanks to the water balance calculation (Fig.…”

Section: 1mentioning

confidence: 88%

Hydrogeological conceptual model of andesitic watersheds revealed by high-resolution geophysics

Vittecoq¹,

Reninger²,

Lacquement³

et al. 2019

Preprint

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We conducted a multidisciplinary study at the watershed scale of an andesitic-type volcanic island in order to better 10 characterize the hydrogeological functioning of aquifers and to better evaluate groundwater resource. A helicopter-borne TDEM survey was conducted in 2013 over Martinique Island in order to investigate underground volcanic structures and lithology, characterized by high lateral and vertical variability, and resulting in a very high heterogeneity of their hydrogeological characteristics. Correlations were made on three adjacent watersheds between resistivity data along flight lines and geological and hydrogeological data from 51 boreholes and 24 springs, showing that the younger the formations, the 15 higher their resistivity. Correlation between resistivity, geology and transmissivity data of three aquifers is attested: the older the formation, the lower its resistivity, and the higher its transmissivity. Moreover, we demonstrate that the main geological structures lead to preferential flow circulations and that hydrogeological watershed can differ from topographical watershed.The consequence is that even if the topographical watershed is small, underground flow circulations can add significant amount of water to river watershed's water balance. This effect is amplified when lava domes and their roots are situated upstream, as 20 they present very high hydraulic conductivity leading to deep preferential groundwater flow circulations. We also reveal, unlike basaltic-type volcanic islands, that hydraulic conductivity increases with age in this andesitic-type volcanic island. This trend is interpreted as the consequence of tectonic fracturing associated to earthquakes in subduction zones associated to andesitic volcanic islands. Finally, our approach allows characterizing in detail the hydrogeological functioning and identifying the properties of the main aquifer and aquitard units, leading to the proposition of a hydrogeological conceptual model at the 25 watershed scale. This working scale seems particularly suitable due to the complexity of edifices, with heterogeneous geological formations presenting high lateral and vertical variability. Moreover, our study offers new guidelines for accurate correlations between resistivity, geology and hydraulic conductivity for volcanic islands. Finally, our results will also help stakeholders toward a better management of water resource.Hydrol. Earth Syst. Sci. Discuss., https://doi.

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Hydrogeological settings of a volcanic island (San Cristóbal, Galapagos) from joint interpretation of airborne electromagnetics and geomorphological observations

Cited by 26 publications

References 50 publications

Hydrogeophysical Characterization in a Volcanic Context From Local to Regional Scales Combining Airborne Electromagnetism and Magnetism

Hydrogeophysical Characterization in a Volcanic Context From Local to Regional Scales Combining Airborne Electromagnetism and Magnetism

Combining Clustering Methods With MPS to Estimate Structural Uncertainty for Hydrological Models

Hydrogeological conceptual model of andesitic watersheds revealed by high-resolution geophysics

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