Hydrogeological implications of active tectonics in the Great Artesian Basin, Australia
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Drainage system (geomorphology)
The Minou fault is an active fault system and runs through 25km long from Kurume City to Ukiha Town, North Kyushu, Southwest Japan. The fault is considered as the source fault of Tsukushi great earthquake that occurred at 679A.D. We carried out geophysical surveys such as gravity, controlled source magnetotelluric and γ-ray intensity survey, at the western part of the Minou fault to discuss the subsurface structure around the fault. Based on the gravity survey, the conspicuous graben structure was detected as the low Bouguer anomaly at the north side of the fault. The maximum depth of the graben was estimated at around 2km deep. A steep slope dipping to northward appeared at the south side of the graben and located at 0.5 to 1km north of the active fault line drawn by the topographic discontinuity. The difference of resistivity structure was also detected at the same place. These results show that a buried fault is located at 0.5 to 1km north of the active fault. A marked displacement of the basement was not detected by the gravity data nor the resistivity structure at the active fault. We interpreted that the fault seemed to have been active at the south wall of the graben before the Alluvium. The active place was moved to the south and the new activity has been started at the topographic discontinuity in recent time. These fault displacement suggests that extensional movement has been prevailing in this area during Quaternary.
Half-graben
Horst and graben
Magnetotellurics
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Horst and graben
Half-graben
Normal fault
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Horst and graben
Neotectonics
Half-graben
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The number of unregistered artesian wells increases every year in the northern slopes of Bromo Volcano, Pasuruan. Artesian wells are used for domestic needs and agricultural irrigation but are not followed by environmentally sound groundwater use. The purpose of this study is to assess the potential for groundwater, groundwater use, wasted groundwater, and recommendations for groundwater management. The groundwater potential was obtained by measuring the depth of the groundwater table, piezometric surface of artesian wells, and geoelectrical data. Water uses were obtained from calculations based on the Indonesian National Standard. The amount of wasted groundwater was obtained by comparing the groundwater potentials, groundwater uses, and groundwater discharges from unregistered artesian wells. Water transfer was assessed by selecting unregistered artesian wells with discharges able to fulfill the water demands of each village. Groundwater in the Sub-Districts of Gondang Wetan and Winongan has high potential consisting of 1 unconfined aquifer group and two confined aquifer groups. Gondang Wetan and Winongan Sub-Districts are characterized as wasting groundwater potential through unregistered artesian wells. The discharge flow of unregistered artesian wells exceeds the water needs (>100%) in Winongan and Gondang Wetan Sub-Districts. Groundwater can be managed by water transfer, closure of artesian wells, and regulation of artesian wells use. Water can be transferred to areas not covered by Artesian wells in 20 villages. The number of artesian wells used for water transfer is 20 with a discharge of 5-20 liters/s.
Groundwater discharge
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The Turonian-Coniacian aquifer system in the North of the Coastal Sedimentary Basin, southern Benin, West Africa. The Turonian-Coniacian aquifer is the major aquifer in southern Benin and is the main source of water supply for the population. The pressure on groundwater resources from the Turonian-Coniacian aquifer is increasing since few artesian wells tapping into this aquifer already show decrease in their yields. Preventing extinction of the artesian outflows requires as a first step a thorough understanding of the groundwater flow system: groundwater recharge areas, downstream areas, and flow directions. In this study, a combined hydrogeological, hydrochemical and isotopic approach was applied to understand the groundwater flow within this aquifer and to develop a coherent conceptual groundwater flow model. The piezometric results indicated three main groundwater flow directions. Stable isotopes results confirmed the piezometry as the most depleted and enriched values in Oxygen-18 and deuterium were found respectively in downstream areas (southern region) and in the recharge areas (northern region) indicated by the piezometry. Similarly, higher tritium contents (up to 3.5 Tritium Unit) characterize recharge areas and low tritium contents (<0.12 Tritium Unit) were found in downstream areas. The combination of these results with the geologic and topographic data led to a coherent conceptual groundwater flow model shown in this paper.
Groundwater model
Groundwater discharge
Depression-focused recharge
Environmental isotopes
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The Great Artesian Basin (GAB), Australia, contains several groundwater types within the Lower Cretaceous‐Jurassic confined aquifer system with distinctly different chemistry. The groundwater flow pattern of the GAB has been analyzed with over 40 36 Cl measurements from this study and that of Bentley et al. (1986 a ). The results indicate general agreement between the hydrologie model ages (Darcy's law) and the radioisotopic model ages suggesting that flow conditions over ∼1 m.y. have remained largely unchanged. The results confirm that the chemically distinct western GAB operates as a separate flow system with its own recharge area and its own geochemical evolution. The results indicate an area of groundwater with relatively young 36 Cl ages in the central portion of the basin which cannot be explained by flow or mixing along the presently known flow lines. It is hypothesized that an additional source of young water originated from the basin margin region to the north and northwest between the Simpson Desert and Mount Isa. This additional recharge area, active more strongly over the last 500 kyr than at present, is delineated by 36 Cl ages which integrate a history and evolution over the age of the groundwater.
Groundwater discharge
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Abstract Artesian water is groundwater that flows freely at the surface from an artesian bore or well. The name artesian comes from the flowing wells constructed in the twelfth century at the Carthusian monastery near Lilliers in the northeastern French province of Artois. The artesian condition is, however, an accident of topography, not necessarily a property of the water, the bore, or the aquifer. For this reason, it is preferable now to use the term ‘confined’ to refer to the aquifer. ‘Confined’ implies the presence of a low permeability confining bed above the confined aquifer, which allows a positive (above ground) hydraulic head to be maintained. Rarely, flowing water can be obtained from an unconfined aquifer without a confining bed, provided there is a sufficient upward head gradient. Artesian water is common in sedimentary basins, where there are extensive aquifers overlain by confining beds. The classic artesian basin is shaped like a saucer; the aquifer crops out around the elevated margins of the basin, where it can be recharged by rainfall or stream flow. The cities of London and Paris lie at the centers of their basins and were among the first cities to exploit artesian water on a large scale. The Great Artesian Basin in eastern Australia is one of the largest examples; it is 1500 km across. However, artesian conditions can occur in other geological formations.
Hydraulic head
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