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| Titel |
Ground-water Exploration in Regolith-bedrock Aquifer: A Case Study in the Basins of Mid-Jhuoshuei River and Beigang River, Central Taiwan |
| VerfasserIn |
Shih-Meng Hsu, Chien-Chung Ke, Yen-Tu Lin, Ji-Jao Huang |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048211
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| Zusammenfassung |
| Due to climate influence and subsidence hazard in plain areas, ground-water resources from
mountainous regions have been considered as an alternative water source in Taiwan. To
understand potential yield of ground-water resources in Taiwan Mountainous Region,
information regarding hydrogeological framework of regolith-bedrock aquifer must first be
explored. This paper emphasized and presented on this issue. This study conducted
hydrogeological investigation for regolith-bedrock aquifers in the basins of Mid-Jhuoshuei
River and Beigang River, Central Taiwan. The study site covers an area of 1530 square
kilometres and contains 23 geological units. The investigation content includes surficial
geology investigations, borehole drilling (29 drilling boreholes and 3000 meters drilling
length in total), borehole hydrogeological tests (borehole televiewer, caliper, borehole
electrical logging, sonic logging, flowmeter measurement, and double pack test), and
laboratory tests from rock core samples (physical properties test of soil and rocks, triaxial
permeability test of soil, porosity determination test using mercury air pump and helium, gas
permeability test, laser particle size analyzing test, X-ray diffraction test, and petrographic
analysis).
Borehole drilling results show that the groundwater system in the mountainous region is
essentially a two-part system comprised of the regolith and the underlying bedrock. The
regolith thickness, which may be related to slope, curvature, and elevation of a study site, is
highly variable, and the average of regolith thickness is approximately 18 meters. The
regolith thickness can reach up to 50 meters at colluvium sties and serves as the principal
storage reservoir for the underlying bedrock. The shallow regolith and underlying bedrock
fractures are connected, the aquifer systems of the study region are mostly considered to be
unconfined.
Hydrogeological investigation results at both in-situ and laboratory scale indicate porosity
on different geological formations is within 30%. Tachien Shale, Shihpachungsi formation,
and Paileng Formation have relatively low porosity. Toukoshan Formation Houyenshan
Member, Toukoshan Formation Hsiangshan Member, and Changhukeng Shale have relatively
high porosity. Hydraulic conductivity ranges from the magnitudes between 10-4-10-10 m/s.
Kueichulin formation Kuantaoshan Sandstone Member, Paileng Formation, Tachien Shale,
and Nanchuang Formation have relatively high hydraulic conductivity. Shuichangfu
Formation, Toukoshan Formation Hsiangshan Member, and Cholan Formation have relatively
low hydraulic conductivity. Additionally, permeable zone at different lithologic units,
the correlation of the fracture features and their interconnectivity, location of the
water-receiving or producing zone, the water-bearing zone and their corresponding fracturing
degree, as well as the hydraulic properties at different depths of a borehole can be
identified. Finally, the aforementioned results were carried out to further characterize the
hydrogeologic system of the site and quantitatively determine the hydraulic properties
of major hydrogeologic units. This effort, at the same time, brings information
to establish a hydrogeologic conceptual model and process the model simulation
for evaluating potential yield of ground-water resources within the study region. |
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