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Hydrogeology Journal

, Volume 16, Issue 2, pp 363–372 | Cite as

Gradient profiling for the investigation of groundwater saturated fractures in hard rocks of Uttar Pradesh, India

  • G. S. Yadav
  • Shashi Kant Singh
Report

Abstract

Gradient profiling (GP) has been successfully utilized as a preliminary tool to identify fractured zones saturated with groundwater in hard-rock areas of Robertsganj, Sonebhadra district, Uttar Pradesh, India. Conducting geoelectrical sounding at randomly selected places may not provide fruitful results since fractures are sparsely distributed in hard rocks. In gradient profiling, current electrodes with large separation remain fixed while the potential dipole is moved between the current electrodes in the central one-third portion of the profile at a small station interval. A GP survey was conducted along seven profiles having different lengths in two small sectors of the study area. Low resistive zones have been identified which correspond to the fractured zones. A few geoelectrical soundings were carried out to investigate the depth and thickness of the fractured zones. Two test boreholes, one drilled in each sector, yielded continuous discharge of fresh water (18,000–24,000 L/h). The present study confirms the findings of previous work that the GP survey is a powerful initial technique that identifies the presence of a fractured zone, especially in a hard-rock area covered with a thin soil layer.

Keywords

Gradient profiling India Resistivity surveys Groundwater exploration Fractured rocks 

Resumen

Les profils de gradient ont été utilisés avec succès comme premier outil d’identification des zones de fractures saturées en eau souterraine dans l’environnement cristallin de Robertsganj (district de Sonebhadra, Uttar Pradesh, Inde). La réalisation de sondages géoélectriques sur des implantations aléatoires peut produire des résultats infructueux, du fait même de la distribution éparse des fractures dans les roches cristallines. Dans le cas des profils de gradient, les électrodes de courant restent fixes avec un grand espacement, tandis que le dipôle potentiel est déplacé sur de faibles intervalles dans le tiers central de l’espace entre les deux électrodes de courant. Une campagne a été réalisée sur sept profils de longueurs différentes, dans deux secteurs de la zone d’étude. Des zones peu résistives ont été identifiées ; elles correspondent aux zones fracturées. Quelques sondages géoélectriques ont été réalisés afin d’identifier la profondeur et l’épaisseur des zones fracturées. Les deux sondages de reconnaissance (un par secteur) ont chacun produit un débit continu d’eau douce compris entre 18,000–24,000 L/h. La présente étude confirme les résultats de travaux précédents : les profils de gradient constituent une technique solide d’investigation préliminaire pour identifier les zones de fractures, notamment dans les roches cristallines recouvertes d’un sol peu épais.

Résumé

El Perfilaje de Gradiente (GP) se ha utilizado con éxito, como una herramienta preliminar para identificar zonas fracturadas y saturadas con agua subterránea, en áreas de rocas duras de Robertsganj, en el distrito de Sonebhadra, Uttar Pradesh, India. La ejecución de sondeos geoeléctricos, en sitios seleccionados al azar, podría no proporcionar resultados fructíferos, ya que las fracturas están escasamente distribuidas en las rocas duras. En el perfilaje de gradiente, los electrodos existentes con una separación grande, permanecen fijos, mientras el dipolo de potencial se mueve a un intervalo pequeño entre estaciones y entre los electrodos existentes, en la porción central, la cual es equivalente a un tercio del perfil. Un estudio de GP se ejecutó a lo largo de siete perfiles, con longitudes diferentes, en dos sectores pequeños del área del estudio. Se han identificado zonas de baja resistividad, qué corresponden a las zonas fracturadas. Se llevaron a cabo unos pocos sondeos geoeléctricos para investigar la profundidad y espesor de las zonas fracturadas. Dos perforaciones de prueba, una en cada sector, produjeron descargas continuas de agua dulce (18,000–24,000 L/h). El estudio presente confirma los resultados de trabajos anteriores, en el sentido que un estudio de GP es una técnica inicial poderosa, que identifica la presencia de una zona fracturada, sobre todo en áreas de rocas duras cubiertas con una capa de suelo delgado.

Notes

Acknowledgements

Authors are grateful to the Department of Geophysics, Banaras Hindu University for providing the necessary facilities required for the geoelectrical survey and also thankful to Prof. T. Lal, Department of Geophysics, Banaras Hindu University for critically going through the manuscript. Valuable and thoughtful suggestions given by the reviewers and editors are thankfully acknowledged. Financial support given by Bharat Sanchar Nigam Limited, Uttar Pradesh and India Reserve Vahini, Uttar Pradesh are duly acknowledged.

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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.Department of Geophysics, Faculty of ScienceBanaras Hindu UniversityVaranasiIndia

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