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Delineating groundwater potential zones using an integrated geospatial and geophysical approach in Phuentsholing, Bhutan

Gyeltshen Sangay, Kannaujiya Suresh, Chhetri Indra Kumar, Chauhan Prakash

Acta Geophysica

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2023

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Vol. 71, no. 1

341--357

EN

Groundwater can serve as an alternative measure to solve the scarcity in perennial water sources. In this perspective, a study has been carried out in Phuentsholing, Bhutan, for demarcating the most probable zone for groundwater source by an integrated application of geospatial and geophysical survey. The seven contributing factors (i.e. geology, geomorphology, drainage, landuse landcover (LULC), normalized difference vegetation index (NDVI), lineament, and slope are evaluated. Subsequently, an Analytic Hierarchy Process (AHP) is also carried out to normalize the weightage and rank of the individual factors, which are further overlaid using the Weighted Index Overlay (WIO) algorithm. The resultant groundwater potential was categorized into: extremely high (0.7%), high (54%), moderate (12.5%), low (21%), and extremely low (12%) potential zones. Each of this category is further validated by Vertical Electrical Sounding (VES-3) using Schlumberger electrode configuration and identified the most probable groundwater exploration zones towards the south-western parts of the study area. Thus, the study emphasizes on significant role of remote sensing and geographic information system (GIS) in aggregation with the geophysical and statistical measures to delineate the most probable location for groundwater resources in the Himalayan region.

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Assessing the efects of 1D assumption violation in vertical electrical sounding (VES) data processing and interpretation

Mashhadi Seyyed Reza, Ramazi Hamidreza, Asgarpour Shahreza Mohammad

Acta Geophysica

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2020

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Vol. 68, no. 1

105--122

EN

This research aimed to discover the possible efects of 1D assumption violations on VES data interpretations. In order to do so, 1D inversion results of logarithmically spaced and linearly spaced VES measurements are compared with their relevant 2D inverted models. Some real case studies are also examined by 1D and 2D inversions to test the results. It is found that linearly spaced VES measurements are not really suitable for 1D inversion in the case of 1D assumption violations and logarithmically spaced VES can better handle these problematic features. In the case of semi-infnite horizontal layers and also small surface resistivity inhomogeneities, logarithmically spaced VES datasets mostly provide a reliable 1.5D model while linearly spaced VES datasets sufer from remarkable artifacts. In the case of vertical structures, both linearly spaced and logarithmically spaced VES techniques fail. In this case (i.e., a vertical dike), artifacts in the form of “extra layer” appear in those VES stations that are adjacent to the dike. However, for VES stations on the dike structure, no extra layer appears in the 1D inversion result. It must be emphasized that 1D violating features are not improbable in many geological situations so they must be considered in mind when processing and interpreting the geophysical VES data.

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Analiza porównawcza wyników badań geofizycznych i geologiczno inżynierskich na potrzeby ustalania modelu geologicznego – na przykładzie poligonu badawczego Kępa Włocławska

Gańko M., Mieszkowski R, Gańko A.

Przegląd Geologiczny

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2015

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Vol. 63, nr 2

121–-130

EN

The paper present the correlation of geophysical method with geological-engineering data. As an experimental testing ground, a terrain with simple soil conditions was selected, located on the W³oc³awek River-islet. This is a large alluvial area on the Vistula River, downstream of the W³oc³awek Dam. In the study, the following geophysical methods were applied: vertical electrical sounding (VES), refraction seismic, ground penetrating radar (GPR) and electrical resistivity tomography (ERT). The evaluation of geological-engineering conditions was executed by using the following methods: drilling, cone penetration test (CPT sounding), measurements of the underground water level and macroscopic and laboratory analyses of soils samples. The results obtained were described and presented in a graphic form.