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1
Wu, Peipeng, Jean-Christophe Comte, Lijuan Zhang, Shuhong Wang e Bin Chang. "Effect of Surface Water Level Fluctuations on the Performance of Near-Bank Managed Aquifer Recharge from Injection Wells". Water 13, n. 21 (27 ottobre 2021): 3013. http://dx.doi.org/10.3390/w13213013.
Testo completoAbstract (sommario):
Managed aquifer recharge operations are often conducted in near-bank areas to regulate water resources or reduce seawater intrusion. Yet little is known about the influence of surface water level fluctuations at different temporal scales on MAR performance. A generalized conceptual model was developed based on an investigation site in Western China as a basis to simulate the response surface water level fluctuations on the water table, artificially recharged water lens (formed by the artificially recharged water), groundwater flow paths and average travel times (which is an important control on how quickly contaminants are flushed out of aquifers), and the discharge of the artificially recharged aquifer during the surface water level fluctuation. The results showed a fluctuating groundwater table in the artificially recharged near-bank aquifer under the influence of surface water level fluctuations. The peak values of the increment of the groundwater table induced by artificial recharge decreased with the increase of the period and amplitude of surface water level fluctuation, but the trough values of the increment of water table increases with that. The penetration depth of surface water into the aquifer with a fluctuating surface water level leads to a decreasing increment of the groundwater table which follows a power law. The fluctuating surface water level leads to dynamic changes of artificially recharged water lens morphology and a thinner artificially recharged water lens. A mixing zone of recharged water and ambient water could be found in the artificially recharged near-bank area, which is expected to lead to modifications in the geochemical conditions in the artificially recharged near-bank aquifer. A longer period of surface water level fluctuation leads to a longer average travel time, but the larger penetration depth of surface water and amplitude lead to a shorter average travel time. The peak discharge of the near-bank aquifer was found to decrease with the period of surface water level fluctuation, but it increases with penetration depth and amplitude. This study is important in providing insights into the performance of near-bank managed aquifer recharge with respect to surface water level fluctuation.
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Sugiyanto, Didik, Ibnu Rusydy, Marwan Marwan, Dian Mutia Hidayati e Asrillah Asrillah. "A PRELIMINARY STUDY ON AQUIFER IDENTIFICATION BASED ON GEO-ELECTRICAL DATA IN BANDA ACEH, INDONESIA". Jurnal Natural 18, n. 3 (4 ottobre 2018): 122–26. http://dx.doi.org/10.24815/jn.v18i3.11204.
Testo completoAbstract (sommario):
The aquifers exploration has been conducted at the western part of Banda Aceh, Indonesia. This research aims to explore the aquifer layer beneath the surface and to obtain the cross-section model of the aquifer. The Vertical Electrical Sounding (VES) method was applied to investigate the aquifer layer. The VES method worked as the current penetrated into the ground using of two electrodes and the potential response due to its current being measured by another two electrodes. Ten grid points of VES has performed in western part of Krueng Aceh of Banda Aceh using the ARES (Automatic Resistivity Meter). The Res1Dinv and curve matching computer software used in VES data processing and analysis. The result shows the resistivity value of aquifer in Banda Aceh city at the range of 1 – 12 Ωm for freshwater, and 0.1 – 0.6 for brackish water layer. The first aquifer (water table) found at a depth of 0.5 to 2 meters beneath the surface. The 2-meters water table mostly located near the coastal zone or downstream zone of Krueng Aceh basin and shallow depth of 0.5 meters on the upstream. More than one aquifer layers were found beneath the surface, they were separated by aquitard layer consisting of silt to clay layers.
3
Wumu, Rizky Hizrah, Ahmad Zainuri e Noviar Akase. "Karakteristik Akuifer Menggunakan Metode Geolistrik Resistivity Di Kecamatan Kota Tengah Kota Gorontalo". Jambura Geoscience Review 4, n. 1 (24 gennaio 2022): 60–68. http://dx.doi.org/10.34312/jgeosrev.v4i1.12752.
Testo completoAbstract (sommario):
Kota Tengah Subdistrict has the highest population density in Gorontalo City, with a population density of 6,755 people/km2. This high population density requires a large amount of water to meet the needs of the population, where one form of fulfillment is taken from groundwater. For this reason, it is necessary and important to know the characteristics of aquifers. This study aims to determine the characteristics of groundwater aquifers in the Kota Tengah Subdistrict. The method used is the resistivity geoelectric method to obtain aquifer characteristics in the form of material type (lithology), depth, and thickness of the aquifer. Based on the geoelectrical analysis in TS 01 there are 4 layers, namely topsoil, clay sand, sand, and clay; TS 02 contains topsoil, sand, and clay layers; TS 03 contains topsoil, sand, and clay. The study found that the lithology of the near-surface layer in the Kota Tengah subdistrict can be classified into aquifers and aquicludes. The aquifer layer is formed by sand-sized sedimentary deposits that have high permeability while the aquiclude is clay-sized which is impermeable. The aquifer layer was found starting from a depth of 0.57 m. The average thickness of the aquifer layer was 13.8 m which is interpreted as an unconfined aquifer. This study also found other deeper aquifer layers as confined aquifers that can not be further interpreted due to the limitations of the method used.
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Kocar, Benjamin D., Shawn G. Benner e Scott Fendorf. "Deciphering and predicting spatial and temporal concentrations of arsenic within the Mekong Delta aquifer". Environmental Chemistry 11, n. 5 (2014): 579. http://dx.doi.org/10.1071/en13244.
Testo completoAbstract (sommario):
Environmental context Himalayan derived arsenic contaminates groundwater across Asia, ranging from the deltas of Ganges-Brahmaputra of Bangladesh to the interior basins of the Yangtze and Yellow Rivers in China, where more than one hundred million people are drinking water with hazardous levels of the toxin. Our ability to predict the distribution and changes in arsenic concentration in aquifers of affected regions has been limited. Here we provide a dynamic model that captures arsenic migration and can be used to forecast changes in groundwater arsenic concentrations. Abstract Unravelling the complex, coupled processes responsible for the spatial distribution of arsenic within groundwaters of South and South-East Asia remains challenging, limiting the ability to predict the subsurface spatial distribution of arsenic. Previous work illustrates that Himalayan-derived, near-surface (0 to 12m) sediments contribute a substantial quantity of arsenic to groundwater, and that desorption from the soils and sediments is driven by the reduction of AsV and arsenic-bearing iron (hydr)oxides. However, the complexities of groundwater flow will ultimately dictate the distribution of arsenic within the aquifer, and these patterns will be influenced by inherent physical heterogeneity along with human alterations of the aquifer system. Accordingly, we present a unified biogeochemical and hydrologic description of arsenic release to the subsurface environment of an arsenic-afflicted aquifer in the Mekong Delta, Kandal Province, Cambodia, constructed from measured geochemical profiles and hydrologic parameters. Based on these measurements, we developed a simple yet dynamic reactive transport model to simulate one- and two-dimensional geochemical profiles of the near surface and aquifer environment to examine the effects of subsurface physical variation on the distribution of arsenic. Our results show that near-surface release (0–12m) contributes enough arsenic to the aquifer to account for observed field values and that the spatial distribution of arsenic within the aquifer is strongly affected by variations in biogeochemical and physical parameters. Furthermore, infiltrating dissolved organic carbon and ample buried particulate organic carbon ensures arsenic release from iron (hydr)oxides will occur for hundreds to thousands of years.
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Mažeika, Jonas, Tõnu Martma, Rimantas Petrošius, Vaidotė Jakimavičiūtė-Maselienė e Žana Skuratovič. "Radiocarbon and Other Environmental Isotopes in the Groundwater of the Sites for a Planned New Nuclear Power Plant in Lithuania". Radiocarbon 55, n. 2 (2013): 951–62. http://dx.doi.org/10.1017/s0033822200058100.
Testo completoAbstract (sommario):
The assessment of construction sites for the new Visaginas Nuclear Power Plant (Visaginas NPP), including groundwater characterization, took place over the last few years. For a better understanding of the groundwater system, studies on radiocarbon; tritium; stable isotopes of hydrogen, oxygen, and carbon; and helium content were carried out at the location of the new NPP, at the Western and Eastern sites, as well as in the near-surface repository (NSR) site. Two critical depth zones in the Quaternary aquifer system were characterized by different groundwater residence times and having slightly different stable isotope features and helium content. The first shallow interval of the Quaternary multi-aquifer system consists of an unconfined aquifer and semiconfined aquifer. The second depth interval of the system is related to the lower Quaternary confined aquifer. Groundwater residence time in the first flow system was mainly based on tritium data and ranges from 6 to 60 yr. These aquifers are the most important in terms of safety assessment and are considered as a potential radionuclide transfer pathway in safety assessment. Groundwater residence time in the lower Quaternary aquifers based on 14C data varies from modern to several thousand years and in some intervals up to 10,500 yr.
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HENRY, J. L., P. R. BULLOCK, T. J. HOGG e L. D. LUBA. "GROUNDWATER DISCHARGE FROM GLACIAL AND BEDROCK AQUIFERS AS A SOIL SALINIZATION FACTOR IN SASKATCHEWAN". Canadian Journal of Soil Science 65, n. 4 (1 novembre 1985): 749–68. http://dx.doi.org/10.4141/cjss85-080.
Testo completoAbstract (sommario):
The stratigraphy and hydrology of saline soils were investigated at 15 sites in Saskatchewan, Canada. At five sites (Series A) nests of piezometers were installed and at 10 sites (Series B) a single piezometer was installed in or near an aquifer. Piezometric surface data from the nests showed the potential for upward movement in all Series A sites. The electrical conductivity (EC) of water from Series A piezometers increased from the deepest to shallowest and there was a general increase in soil EC towards the soil surface. Hydraulic conductivity of strata was measured at three sites and varied from 1.6 × 10−7 to 3.2 × 10−4 cm∙sec−1. It was calculated that observed salt loads for the three sites could accumulate by upward movement from the aquifer in from 500 to 5300 yr. For Series B sites the approximate sodium percentage (ASP) of the soil (Y) was related to the ASP of the aquifer (X) by the equation:[Formula: see text]For Series A and Series B sites combined the EC (dS∙m−1) of the 1:1 suspension of the stratum immediately above the aquifer (Y) was related to the EC of the aquifer (X) by the equation:[Formula: see text]Key words: Soil salinity, aquifers, stratigraphy, salt profiles
7
Darsono, Darsono, Ahmad Marzuki, Nuryani Nuryani e G. Yuliyanto. "Detection of groundwater aquifers using geoelectrical resistivity method (case study : Plupuh Sub-district, Sragen District )". Journal of Physics: Conference Series 2498, n. 1 (1 maggio 2023): 012004. http://dx.doi.org/10.1088/1742-6596/2498/1/012004.
Testo completoAbstract (sommario):
Abstract An aquifer is a layer below the ground surface that contains groundwater. Inside the earth there are unconfined aquifers and confined aquifers, where unconfined aquifers are located near the surface while confined aquifers are located very deep beneath the earth. This study aims to find the location, depth, and thickness of aquifers that have the potential to contain large amounts of groundwater. The instrument used in this research is a resistivity meter OYO Model 2119C Mc OHM-EL, with a Schlumberger configuration with a current electrode length of AB/2 to 350 meters. Data acquisition were carried out in the Plupuh sub-district, Sragen district as many as 5 sounding points, and data processing using IP2win software. Based on the interpretation of resistivity geoelectrical data, it can be concluded that the area has the potential to have a lot of groundwater content, for unconfined aquifers at the TS1 sounding point with a depth of 7.7 meters to 19.2 meters with a thickness of 11.5 meters. and TS4 with a depth of 15.4 meters to 30 meters with a layer thickness of 14.6 meters. This aquifer layer is dominated by sand layer lithology, while the confined aquifer layer is located around TS1 and TS2. The two sounding points are located in the east and northeast of the research area. TS1 was detected at a depth of 39.9 meters to 110 meters with a layer thickness of 60.1 meters and TS2 was at a depth of 40.2 meters to 66.5 meters and 80.2 meters to 139.7 meters with a thickness of 84.8 meters. This aquifer layer is dominated by the gravel sand layer in TS1 and the sand layer in TS2.
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Hinzman, Larry D., Matthew Wegner e Michael R. Lilly. "Hydrologic Investigations of Groundwater and Surface-water Interactions In Subarctic Alaska". Hydrology Research 31, n. 4-5 (1 agosto 2000): 339–56. http://dx.doi.org/10.2166/nh.2000.0020.
Testo completoAbstract (sommario):
Dynamic interactions between rivers and adjacent aquifers can significantly affect near-bank geochemistry and processes associated with natural attenuation of contaminants by mixing water or introducing oxygen or nutrients. During 1997 and 1998 in a study near Fairbanks, Alaska U.S.A, the hydrologic conditions in the Chena River and in the adjacent groundwater were monitored. The river stage, groundwater elevations, and the water chemistry and temperature in both river and groundwater were measured. In the spring of 1997, the groundwater gradient close to the Chena River reversed causing surface water to enter the aquifer. Changes in temperature, specific conductance and alkalinity were used to determine the extent of bank recharge. For approximately one week during spring snowmelt of 1997, surface-water influx from the Chena River occurred approximately between the depths of 5.33 m and 9.1 m below ground surface. The effects of bank recharge extended at least 6.1 m but not to 30.5 m from the banks of the Chena River into the aquifer. Bank recharge caused 64 to 68 per cent of the groundwater, 6.1 m from the bank at a depth of 6.78 m to be displaced by surface water influx. Peak flows during 1998 were not high enough to cause flow reversals.
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Mukherjee, S., E. A. Mohammad e R. H. Worden. "Satellite data interpretation of causes and controls on groundwater-seawater flow directions, Merseyside, UK: implications for assessing saline intrusions". Hydrology and Earth System Sciences Discussions 2, n. 3 (9 giugno 2005): 887–916. http://dx.doi.org/10.5194/hessd-2-887-2005.
Testo completoAbstract (sommario):
Abstract. Groundwater in the Triassic Sherwood Sandstone aquifer, Liverpool, UK, has locally elevated chloride concentrations (~4000 mg/l) in parts of the coastal region although there is freshwater right up to the coast line in other areas. The aquifer is cut my numerous faults with vertical displacements of as much 300 m. SPOT satellite data have been used for the Merseyside area of Liverpool. The satellite data revealed and confirmed the location of some of the main faults since the fault zones of the aquifer have low permeability (due to grain crushing, cataclasis, and clay smearing). Where fault zones outcrop at the surface, below the well-developed regolith, there is locally elevated soil water and thus anomalous vegetation patterns in comparison to unfaulted and highly porous aquifer. The ability to identify fault zones by this satellite-based method strongly suggests that they are at least partially sealing, sub-vertical features in the aquifer. Digitally enhanced and processed satellite data were used to define the relative proportions of sand and clay in the near-coastal (inter-tidal) part of the Mersey estuary. Sand-dominated sediment has higher pixel values in comparison with clay deposits in the near infrared spectral region (NIR). Where open and weathered fault rocks crop out at the surface near the intertidal zone, water movement in these potential surface water conduits is limited where the intertidal zone is clay-dominated since clay will plug the conduit. Where these weathered and open fault-rocks crop out against sand-dominated parts of the coastline, fresh water outflux into the seawater has been imaged using the satellite data. Furthermore, the high and low chloride concentration parts of the aquifer are separated by major, sub-vertical fault zones and have allowed a very steep water table gradient to remain in the aquifer.
10
Peñafiel, Lilia, Francisco Javier Alcalá e Javier Senent-Aparicio. "Usefulness of Compiled Geophysical Prospecting Surveys in Groundwater Research in the Metropolitan District of Quito in Northern Ecuador". Applied Sciences 11, n. 23 (24 novembre 2021): 11144. http://dx.doi.org/10.3390/app112311144.
Testo completoAbstract (sommario):
As in other large Andean cities, the population in the Metropolitan District of Quito (MDQ) in northern Ecuador is growing, and groundwater is becoming essential to meet the increasing urban water demand. Quito’s Public Water Supply Company (EPMAPS) is promoting groundwater research for sustainable water supply, and geophysical prospecting surveys are used to define aquifer geometry and certain transient groundwater features. This paper examines the usefulness of existing geophysical prospecting surveys in groundwater research in the MDQ. A database was built using 23 representative geophysical prospecting surveys compiled from EPMAPS’ public repository, official geotechnical research reports, and the scientific literature. Fifteen EPMAPS-promoted surveys used near-surface electrical techniques (seven used electrical resistivity tomography and eight used vertical electrical sounding) to explore Holocene and Pleistocene sedimentary and volcano-sedimentary formations in the 25–500-m prospecting depth range, some of which form shallow aquifers used for water supply. Four other surveys used near-surface seismic techniques (refraction microtremor) for geotechnical research in civil works. These surveys have been reinterpreted to define shallow aquifer geometry. Finally, four surveys compiled from the scientific literature used electromagnetic techniques (magnetotelluric sounding and other very low-frequency methods) to explore Holocene to late Pliocene formations, some of which form thick regional aquifers catalogued as the larger freshwater reservoirs in the MDQ. However, no geophysical prospecting surveys exploring the complete saturated thickness of the Pliocene aquifers could be compiled. Geophysical prospecting surveys with greater penetration depth are proposed to bridge this research gap, which prevents the accurate assessment of the renewable groundwater fraction of the regional aquifers in the MDQ that can be exploited sustainably.
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Deeds, Neil, Michael Turco, Van Kelley, Christina Petersen e Susan Baird. "Assessment of Subsidence Risk Associated with Brackish Groundwater Development in the Coastal Lowlands Aquifer, Houston, Texas, USA". Proceedings of the International Association of Hydrological Sciences 382 (22 aprile 2020): 437–41. http://dx.doi.org/10.5194/piahs-382-437-2020.
Testo completoAbstract (sommario):
Abstract. Significant undeveloped brackish groundwater resources exist within the Coastal Lowlands Aquifer System (Gulf Coast Aquifer System) near Houston, Texas, USA. As the development of these frontier resources is imminent, an improved understanding of the impact development may have on the availability of the resource and land subsidence is needed. In this region, land subsidence is caused by the depressurization of the aquifer and compaction of the many clay lenses in the subsurface. The Gulf Coast Aquifer System in the study area includes three primary water bearing units (from shallow to deep): the Chicot (Pleistocene and Pliocene) and Evangeline (Pliocene and Miocene) aquifers, and the Jasper aquifer (Miocene). Although there has been much research and data supporting the causal relation between water-level decline and subsidence in the areas of fresh groundwater development, little data exists to inform on the potential subsidence impacts upon deeper brackish groundwater development. Data were compiled, and multiple hydrologic parameters were utilized to improve the understanding of the brackish resources within the study area. Geophysical logs were compiled and analysed to refine the aquifer stratigraphy, determine the binary classification of sand and clay, and estimate the groundwater salinity. These data were used to develop a MODFLOW groundwater flow model to estimate the risk of compaction and land subsidence upon the development of brackish zones within the Jasper aquifer. Compiled data detailing the total clay thickness, clay bed thickness, and clay bed location were input into the model along with a hypothetical stress to predict compaction within the Jasper aquifer across the study area while incorporating the observed heterogeneity in clay properties. Using the results from the model simulations and two other risk performance measures (depth of burial and surface flood risk), the total subsidence normalized risk score was estimated. The results of this study confirm the potential for compaction in the Jasper aquifer and for land subsidence to occur upon development. Areas with the highest risk are located in the up-dip, inland areas, near where the aquifer becomes fresh and is currently used for municipal supply. The results will inform water managers and planners in the Houston area on the future availability of brackish groundwater resources.
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Broster, B. E., e D. A. Pupek. "The significance of buried landscape in subsurface migration of dense non-aqueous phase liquids; the case of perchloroethylene in the Sussex Aquifer, New Brunswick". Environmental and Engineering Geoscience 7, n. 1 (1 febbraio 2001): 17–29. http://dx.doi.org/10.2113/gseegeosci.7.1.17.
Testo completoAbstract (sommario):
Abstract At Sussex, New Brunswick, dissolved perchloroethylene (PCE) as high as 28.0 mu g/liter, was detected within the upper aquifer and in concentrations to 1.6 mu g/liter within the lower aquifer that serves as the main source of municipal water supply. Predominantly formed as an esker ridge, the lower aquifer consists of well-sorted, glaciofluvial/ice-contact, sand and gravel layers mostly confined by underlying till and/or bedrock and an overlying unit of laminated silt-clay glaciolacustrine sediments (middle aquitard). The middle aquitard is in turn overlain by an upper aquifer of variable thickness, extending from a depth of about 18 m to near surface, consisting of coarsening-upward sand and gravel, with occasional lenses of clay, silt and diamicton. A dispersal plume was identified by contouring PCE concentrations from 72 samples from the upper aquifer; PCE was not detected in 16 surface soil samples. The highest concentrations imply that the PCE originated from a surface spill near the urban business center and that subsurface migration was influenced significantly by a buried relict river channel cut into the middle aquitard. Scouring along the channel bottom cut through the middle aquitard and intersected the esker ridge of the underlying water supply aquifer, forming windows through the aquitard. Contamination of the lower aquifer has likely originated from the PCE being drawn through these windows during pumping of a water-supply well that is now out of service. Results indicate that withdrawal rates and placement of original municipal water wells, as well as the stratigraphy, conductivity and topography of subsurface units are controlling factors in Dense Non-Aqueous Phase Liquid migration at this site.
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Dzakiya, Nurul, Muhammad Faizal Zakaria, Dewa Gede Eka Setiawan e Robertus Belardo Laksmana. "Study of Groundwater Types Using the Vertical Electrical Sounding (VES) Method in the ‘Martani Field’ Ngemplak District of Yogyakarta". Journal of Applied Geospatial Information 5, n. 1 (27 aprile 2021): 457–61. http://dx.doi.org/10.30871/jagi.v5i1.2703.
Testo completoAbstract (sommario):
Study of groundwater types using the Vertical Electrical Sounding (VES) method in 'Martani Field’ Ngemplak District of Yogyakarta was done by carrying out eight measurement points to look for groundwater potential. This area is an area on the southern slopes of Mount Merapi which is included in the Yogyakarta Groundwater Basin. The type of lithology is identified based on the measurement of its resistivity value so that there are several types of lithology, namely Breccia (110-670 Ωm), Clay (1.99-10.12 Ωm), Sandstones (17.06-56.82 Ωm) and andesite lava (688-1657 Ωm). The bottom of the aquifer in this basin is composed of rock formations that are impermeable or semi impermeable which are non-aquifer, namely by Breccias, Clay and Andesite Lava. The existence of sandstones that act as aquifers is found near the surface at a depth of <25 m and at a depth of about 60-100 m below the surface so that it is divided into two categories, namely shallow groundwater and deep groundwater.
14
Moret, Geoff J., Michael D. Knoll, Warren Barrash e William P. Clement. "Investigating the stratigraphy of an alluvial aquifer using crosswell seismic traveltime tomography". GEOPHYSICS 71, n. 3 (maggio 2006): B63—B73. http://dx.doi.org/10.1190/1.2195487.
Testo completoAbstract (sommario):
In this study, we investigate the use of crosswell P-wave seismic tomography to obtain spatially extensive information about subsurface sedimentary architecture and heterogeneity in alluvial aquifers. Our field site was a research wellfield in an unconfined aquifer near Boise, Idaho. The aquifer consists of a ∼ 20-m-thick sequence of alluvial cobble-and-sand deposits, which have been subdivided into five stratigraphic units based on neutron porosity logs, grain-size analysis, and radar reflection data. We collected crosswell and borehole-to-surface seismic data in wells [Formula: see text] apart. We carefully considered the impact of well deviation, data quality control, and the choice of inversion parameters. Our linearized inverse routine had a curved-ray forward model and used different grids for forward modeling and inversion. An analysis of the model covariance and resolution matrices showed that the velocity models had an uncertainty of [Formula: see text], a vertical resolution of [Formula: see text], and a horizontal resolution of [Formula: see text]. The velocity in the saturated zone varied between [Formula: see text] and [Formula: see text]. Inclusion of the borehole-to-surface data eliminated the X- shaped pattern that is a common artifact in crosswell tomography, and the increased angular coverage also improved the accuracy of the model near the top of the tomogram. The final velocity model is consistent with previous stratigraphic analyses of the site, although the locations of some of the unit boundaries differ by as much as [Formula: see text] in places. The results of this study demonstrate that seismic tomography can be used to image the sedimentary architecture of unconsolidated alluvial aquifers, even when the lithologic contrasts between units are subtle.
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Kotsev, Tsvetan, Sava Kolev e Vladimir Hristov. "Modeling of groundwater flow and transport of pollutants caused by a difference in groundwater densities (on the example of the valley of Vulche dere creek, downstream of Eleshnitsa tailings pond)". Engineering Geology and Hydrogeology 32, n. 1 (2018): 3–12. http://dx.doi.org/10.52321/igh.32.1.3.
Testo completoAbstract (sommario):
An attempt is made to model numerically the transport of dissolved substances caused by a difference in groundwater densities. It is supposed that initially at the surface of the aquifer a sector exists with high concentration of а pollutant (sulphates) while it is zero elsewhere in it. As a result, there is a higher water density near the surface. Due to this difference, a density driven flow arises and starts slow upwelling and downwelling movement of the water. The pollution located initially at the surface moves down and after a period of time reaches the bottom of the aquifer. Unsteady Darcy equation for creeping subsurface flow and mass transfer equation in a porous media were solved simultaneously in 2D area by the finite element method. The geometry of the area used in the calculations follows approximately the real contour of the aquifer. The aim of this study is to predict time needed for given amount of pollution coming from surface water into Quaternary aquifer to reach the lower Neogene aquifer. Plots representing the streamlines of the flow and concentration spreading for different times are shown.
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Jodry, Clara, Dashgin Abakarov, Zaur Bayramov, Javid Aliyev, Nigar Karimova e Murad Abdulla-Zada. "SEG Summer Field Camp: Multigeophysical imaging of an aquifer in the Astara region of Azerbaijan". Leading Edge 43, n. 7 (luglio 2024): 453–58. http://dx.doi.org/10.1190/tle43070453.1.
Testo completoAbstract (sommario):
Groundwater faces growing pressure due to human activities and the impacts of global climate change. Therefore, it is imperative to characterize near-surface aquifers, especially those that are unconfined because they are particularly vulnerable to these challenges. In Azerbaijan, alluvial plain aquifers represent a critical facet of the nation's water resources, yet they remain largely understudied. The objective of our study is to employ a multigeophysical survey (including electrical resistivity, seismic refraction, and ground-penetrating radar) to describe the subsurface attributes of an unconfined alluvial aquifer situated within an agricultural field in Astara, Azerbaijan. These data were acquired during the 2023 SEG Summer Field Camp by global students and specialists. Based on our general knowledge of the area, we interpret our findings as a subsurface with four distinct layers. The first is an initial 1 m thick soil layer covering the second layer, which is a more permeable unconfined aquifer likely consisting of a mixture of sand, pebbles, and gravel with a silty matrix (3 m thick). The third is a potential confining layer that is possibly clayey. The fourth layer is a presumed confined aquifer at a depth of 10 m. These results shed light on previously unstudied alluvial plain aquifers and contribute to comprehension of the hydrogeologic conditions at the local scale. To provide a broader understanding at the regional scale, the survey area should be extended and linked to borehole data to improve the interpretation of the geophysical results.
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Kelson, Vic, e Mark Bakker. "Using periodic analytic elements to analyze aquifer tests near surface waters". Computers & Geosciences 51 (febbraio 2013): 56–63. http://dx.doi.org/10.1016/j.cageo.2012.02.032.
Testo completo
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Guo, Shulan, Changhong Yan, Liangchen Yu e Yang You. "Design of the Supporting Structures for Large and Unusually Shaped Foundation Pit near the Yangtze River". Advances in Civil Engineering 2020 (25 marzo 2020): 1–9. http://dx.doi.org/10.1155/2020/3831805.
Testo completoAbstract (sommario):
A large underground transportation hub is located on the west side of the Nanjing Youth Olympic Center, which is close to the embankment of the Yangtze River. The near-surface primarily comprises newly deposited soft soil of considerable thickness; the lower part is a riverbed-phase sandy soil containing two confined aquifers. The foundation pit requires deep excavation and has unusual shapes of “pit in pit” and “pit leaning pit.” For the convenience and safety of excavation, the piezometric head of the upper confined aquifer, where the pit bottom is located, reached 1 m below the bottom plane through precipitation, while that of the lower confined aquifer also dewatered down to a safe water level to avoid an uplift problem. After considering the engineering geological conditions, the function and shape of the foundation pits, we divided the soil layers of the foundation pits into two areas (the NW area and the SE area) and proposed the support scheme correspondingly. The numerical simulation results and completed construction safely verified the feasibility of the support scheme.
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Somaratne, N., K. Smettem, J. Lawson, K. Nguyen e J. Frizenschaf. "Hydrological functions of sinkholes and characteristics of point recharge in groundwater basins". Hydrology and Earth System Sciences Discussions 10, n. 9 (6 settembre 2013): 11423–49. http://dx.doi.org/10.5194/hessd-10-11423-2013.
Testo completoAbstract (sommario):
Abstract. Karstic limestone aquifers are hydrologically and hydrochemically extremely heterogeneous and point source recharge via sinkholes and fissures is a common feature. We studied three groundwater systems in karstic settings dominated by point source recharge in order to assess the relative contributions to total recharge from point sources using chloride and δ18O relations. Preferential groundwater flows were observed through an inter-connected network of highly conductive zones with groundwater mixing along flow paths. Measurements of salinity and chloride indicated that fresh water pockets exist at point recharge locations. A measurable fresh water plume develops only when a large quantity of surface water enters the aquifer as a point recharge source. The difference in chloride concentrations in diffuse and point recharge zones decreases as aquifer saturated thickness increases and the plumes become diluted through mixing. The chloride concentration in point recharge fluxes crossing the watertable plane can remain at or near surface runoff chloride concentrations, rather than in equilibrium with groundwater chloride. In such circumstances the conventional chloride mass balance method that assumes equilibrium of recharge water chloride with groundwater requires modification to include both point and diffuse recharge mechanisms.
20
Sağır, Çağdaş, Bedri Kurtuluş e Moumtaz Razack. "Hydrodynamic Characterization of Mugla Karst Aquifer Using Correlation and Spectral Analyses on the Rainfall and Springs Water-Level Time Series". Water 12, n. 1 (25 dicembre 2019): 85. http://dx.doi.org/10.3390/w12010085.
Testo completoAbstract (sommario):
Karst aquifers have been an important research topic for hydrologists for years. Due to their high storage capacity, karst aquifers are an important source of water for the environment. On the other hand, it is safety-critical because of its role in floods. Mugla Karst Aquifer (SW, Turkey) is the only major water-bearing formation in the close environs of Mugla city. Flooding in the wet season occurs every year in the recharge plains. The aquifer discharges by the seaside springs in the Akyaka district which is the main touristic point of interest in the area. Non-porous irregular internal structures make the karsts more difficult to study. Therefore, many different methodologies have been developed over the years. In this study, unit hydrograph analysis, correlation and spectral analyses were applied on the rainfall and spring water-level time series data. Although advanced karst formations can be seen on the surface like the sinkholes, it has been revealed that the interior structure is not highly karstified. 100–130 days of regulation time was found. This shows that the Mugla Karst has quite inertial behavior. Yet, the storage of the aquifer system is quite high, and the late infiltration effect caused by alluvium plains was detected. This characterization of the hydrodynamic properties of the Mugla karst system represents an important step to consider the rational exploitation of its water resources in the near future.
21
Boubaya, Djamel. "Combining Resistivity and Aeromagnetic Geophysical Surveys for Groundwater Exploration in the Maghnia Plain of Algeria". Journal of Geological Research 2017 (18 gennaio 2017): 1–14. http://dx.doi.org/10.1155/2017/1309053.
Testo completoAbstract (sommario):
The Maghnia plain in western Algeria is filled by Plio-Quaternary and Miocene sediments that rest unconformably on a basement of Jurassic rocks. Electrical sounding (VES), magnetic data, well information, and hydrogeological data have been used to explore for groundwater potential in the Maghnia plain. The interpretation of Schlumberger sounding data was first calibrated with the lithology of available nearby wells. Four geoelectrical layers were identified within the study area. They are a thin near surface topsoil layer with variable resistivities, a moderate resistive aquifer (15–30 ohm-m), a resistive aquifer (40–70 ohm-m), and a conductive clay layer (1–10 ohm-m). Near Sidi Mbarek, the geoelectric section is reduced to three layers: a topsoil layer, a conductive layer corresponding to the Miocene marls, and a deep resistive layer that correlates with the Oxfordian sandstones. The interpretation of VES data and the enhancement techniques of magnetic data enabled the identification of a number of unmapped faults that occur near recharge zones close to adjacent mountains. This study enabled us to study the extension of the known Plio-Quaternary aquifer of the Maghnia plain and to explore the possible existence of a second deep groundwater aquifer in Oxfordian sandstones.
22
Koehn, Weston J., Stacey E. Tucker-Kulesza e David R. Steward. "Characterizing Riverbed Heterogeneity across Shifts in River Discharge through Temporal Changes in Electrical Resistivity". Journal of Environmental and Engineering Geophysics 25, n. 4 (dicembre 2020): 581–87. http://dx.doi.org/10.32389/jeeg20-049.
Testo completoAbstract (sommario):
The fluxes between groundwater and surface water play a significant role in quantifying water balance along stream reaches to continent scales. Changes in these dynamics are occurring due to aquifer depletion, where pre-development baseflow conditions have transitioned to losing conditions. This problem is studied along the Arkansas River in Western Kansas across a stream reach that transitions from near steady state to losing conditions, and contributes focused recharge to a depleting Ogallala Aquifer. Existing hydrologic data illustrates the lack of understanding they provide related to the control of fluxes exerted by alluvial deposits. Electrical resistivity imaging (ERI) surveys were conducted along this river transect to elucidate the dynamic hydrologic connection existing between the Arkansas River and underlying Arkansas Alluvial and Ogallala Aquifers. Temporal changes in ERI profiles are associated with the transient hydrologic conditions below the water-sediment interface, and complement the hydrogeologic interpretations of the individual ERI profiles. Additionally, fine grained soil inclusions may become revealed by temporal changes in resistivity due to differences in their water holding capacity relative to that of a surrounding matrix of coarser grained soil across changes in recharge. These findings corroborate the role of river-aquifer connectivity and riverbed heterogeneity on localized recharge through embedded assemblages of fine and coarse grained soils.
23
Mari, J. L., e G. Porel. "3D Seismic Imaging of a Near-Surface Heterogeneous Aquifer: A Case Study". Oil & Gas Science and Technology - Revue de l'IFP 63, n. 2 (29 novembre 2007): 179–201. http://dx.doi.org/10.2516/ogst:2007077.
Testo completo
24
MacDonald, Thomas R., e Peter K. Kitanidis. "Modeling the Free Surface of an Unconfined Aquifer Near a Recirculation Well". Ground Water 31, n. 5 (settembre 1993): 774–80. http://dx.doi.org/10.1111/j.1745-6584.1993.tb00850.x.
Testo completo
25
Abu Rajab, Jafar Sadi, e Ali Ramadan El-Naqa. "Mapping groundwater salinization using transient electromagnetic and direct current resistivity methods in Azraq Basin, Jordan". GEOPHYSICS 78, n. 2 (1 marzo 2013): B89—B101. http://dx.doi.org/10.1190/geo2011-0362.1.
Testo completoAbstract (sommario):
Hydrogeophysical characterization using the transient electromagnetic method (TEM) and the DC resistivity sounding (VES) method was implemented in the central part of Azraq Basin (Qa Basin), Jordan, to identify and map the spatial distribution of shallow fresh and saline groundwater in the upper aquifer systems. The alluvium (Al) and chert limestone (URC) shallow aquifers show different degrees of groundwater salinization. The range of groundwater resistivity varies from 0.06 to 10.8 ohm-m. Saline groundwater was detected at depths between 5 to 30 m where the aquifers have a wide spectrum of resistivity values from 0.14 to 120 ohm-m. The integrated geophysical and hydrogeologic models are significantly correlated in chloride concentration, groundwater resistivity, and aquifer resistivity. Using 1D inversion results from the TEM and VES soundings in addition to quasi-3D modeling (1D spatially constrained inversion) at selected TEM sites, groundwater resistivity variation was attributed to two different salinization mechanisms. First, the spatial distribution of the salt content in mud flat deposits had a significant effect on the groundwater salinity. Second, in situ dissolution of near-surface rock-forming salts occurred at areas away from the mud flat deposits. The proposed hydrogeophysical models revealed the potential effect of both mechanisms in the study area.
26
Tokarevsky, O., e I. Iarmosh. "Assessing Impact of Sorption in Geological Medium on Permissible Activity of Radioactive Waste in Near-Surface Disposal Facilities". Nuclear and Radiation Safety, n. 3(75) (22 agosto 2017): 34–39. http://dx.doi.org/10.32918/nrs.2017.3(75).06.
Testo completoAbstract (sommario):
The paper considers the conservative scenario of potential exposure that envisages simultaneous destruction of barriers with simultaneous release of radionuclides by the example of Lot 3 near-surface radioactive waste disposal facility at the Vektor Industrial Complex located in the Chornobyl Exclusion Zone. A conceptual model that considers migration of radionuclides through the aeration zone and aquifer to the potable water well, as well as mixing of infiltration water containing radionuclides with ground water in case of reaching the aquifer, was developed to analyze the mentioned scenario. Permissible specific activity of radioactive waste in the facility is calculated under the assumption that radioactive waste contains only 90Sr radionuclide. Normalysa software is used for calculations.
27
Lewandowski, J., K. Meinikmann, F. Pöschke, G. Nützmann e D. O. Rosenberry. "From submarine to lacustrine groundwater discharge". Proceedings of the International Association of Hydrological Sciences 365 (2 marzo 2015): 72–78. http://dx.doi.org/10.5194/piahs-365-72-2015.
Testo completoAbstract (sommario):
Abstract. Submarine groundwater discharge (SGD) and its role in marine nutrient cycling are well known since the last decade. The freshwater equivalent, lacustrine groundwater discharge (LGD), is often still disregarded, although first reports of LGD are more than 50 years old. We identify nine different reasons why groundwater has long been disregarded in both freshwater and marine environments such as invisibility of groundwater discharge, the size of the interface and its difficult accessibility. Although there are some fundamental differences in the hydrology of SGD and LGD, caused primarily by seawater recirculation that occurs only in cases of SGD, there are also a lot of similarities such as a focusing of discharge to near-shore areas. Nutrient concentrations in groundwater near the groundwater–surface water interface might be anthropogenically enriched. Due to spatial heterogeneity of aquifer characteristics and biogeochemical processes, the quantification of groundwater-borne nutrient loads is challenging. Both nitrogen and phosphorus might be mobile in near-shore aquifers and in a lot of case studies large groundwater-borne nutrient loads have been reported.
28
Kobierska, F., T. Jonas, J. W. Kirchner e S. M. Bernasconi. "Linking baseflow separation and groundwater storage dynamics in an alpine basin (Dammagletscher, Switzerland)". Hydrology and Earth System Sciences 19, n. 8 (25 agosto 2015): 3681–93. http://dx.doi.org/10.5194/hess-19-3681-2015.
Testo completoAbstract (sommario):
Abstract. This study aims at understanding interactions between stream and aquifer in a glacierized alpine catchment. We specifically focused on a glacier forefield, for which continuous measurements of stream water electrical conductivity, discharge and depth to the water table were available over 4 consecutive years. Based on this data set, we developed a two-component mixing model in which the groundwater component was modelled using measured groundwater levels. The aquifer actively contributing to streamflow was assumed to be constituted of two linear storage units. Calibrating the model against measured total discharge yielded reliable sub-hourly estimates of discharge and insights into groundwater storage properties. Our conceptual model suggests that a near-surface aquifer with high hydraulic conductivity overlies a larger reservoir with longer response time.
29
Chen, Xi, Yan-fang Zhang, Xianwu Xue, Zhicai Zhang e Lingna Wei. "Estimation of baseflow recession constants and effective hydraulic parameters in the karst basins of southwest China". Hydrology Research 43, n. 1-2 (1 febbraio 2012): 102–12. http://dx.doi.org/10.2166/nh.2011.136.
Testo completoAbstract (sommario):
By analysing the hydrographs of karst basin outflow, it is possible to identify aquifer characteristics and, accordingly, the main features of a karst basin. In this study, 19 basins with daily observed flow discharges during drought periods between October and April 1973–1983 were selected to analyse the master recession curve (MRC). During a drought period, the MRCs were separated into segments of fast flow exponential recession and slow flow exponential recession. Break points of the fast and slow recession segments were identified and the recession constants α were determined. Relationships between α and basin area were identified. According to the estimated baseflow recession constants, hydraulic parameters including aquifer thickness and hydraulic conductivity were estimated. Hydraulic conductivities in the near-surface epikarst aquifer are of the order 10−3 m s−1, much larger than 10−5 m s−1 in the low-permeability aquifer.
30
Richards, Laura A., Daniel Magnone, Jürgen Sültenfuß, Lee Chambers, Charlotte Bryant, Adrian J. Boyce, Bart E. van Dongen et al. "Dual in-aquifer and near surface processes drive arsenic mobilization in Cambodian groundwaters". Science of The Total Environment 659 (aprile 2019): 699–714. http://dx.doi.org/10.1016/j.scitotenv.2018.12.437.
Testo completo
31
Lauber, U., W. Ufrecht e N. Goldscheider. "Spatially resolved information on karst conduit flow from in-cave dye-tracing". Hydrology and Earth System Sciences Discussions 10, n. 9 (5 settembre 2013): 11311–35. http://dx.doi.org/10.5194/hessd-10-11311-2013.
Testo completoAbstract (sommario):
Abstract. Artificial tracers are powerful tools to investigate karst systems. Tracers are commonly injected into sinking streams or dolines, while springs serve as monitoring sites. The obtained flow and transport parameters represent mixed information from the vadose, epiphreatic and phreatic zones, i.e., the aquifer remains a black box. Accessible active caves constitute valuable but underexploited natural laboratories to gain detailed insights into the hydrologic functioning of the aquifer. Two multi-tracer tests in the catchment of a major karst spring (Blautopf, Germany) with injections and monitoring in two associated water caves aimed at obtaining spatially and temporally resolved information on groundwater flow in different compartments of the system. Two tracers were injected in the caves to characterize the hydraulic connections between them and with the spring. Two injections at the land surface, far from the spring, aimed at resolving the aquifer's internal drainage structure. Tracer breakthrough curves were monitored by field fluorimeters in caves and at the spring. Results demonstrate the dendritic drainage structure of the aquifer. It was possible to obtain relevant flow and transport parameters for different sections of this system. The highest mean flow velocities (275 m h−1) were observed in the near-spring epiphreatic section (open-channel flow), while velocities in the phreatic zone (pressurized flow) were one order of magnitude lower. Determined conduit water volumes confirm results of water balances and hydrograph analyses. In conclusion, experiments and monitoring in caves can deliver spatially resolved information on karst aquifer heterogeneity and dynamics that cannot be obtained by traditional investigative methods.
32
Voloshyn, P. "The flooding of Lviv territory: reasons, patterns of development, ecological consequences". Visnyk of the Lviv University. Series Geography, n. 39 (15 dicembre 2011): 72–77. http://dx.doi.org/10.30970/vgg.2011.39.2164.
Testo completoAbstract (sommario):
Flooding territories of Lviv occupy area more than 50 km2 . The largest area of technogenic flooding belongs to Lviv plateau. Highly dissected parts of Roztochchya belong to nonflooding. Main nature reasons of flooding development are near to surface occurrence waterproof deposits and leveled relief. Technogenic flooding are outflows of water from engineer networks and infraction of surface water. Key words: flooding, technogenic aquifer, soil waters, waterproof deposits, cultural layer, seismicity.
33
Husain, Muin M., John A. Cherry, Scott Fidler e Shaun K. Frape. "On the long-term hydraulic gradient in the thick clayey aquitard in the Sarnia region, Ontario". Canadian Geotechnical Journal 35, n. 6 (1 dicembre 1998): 986–1003. http://dx.doi.org/10.1139/t98-057.
Testo completoAbstract (sommario):
Much of the southwestern part of Ontario between Lake Huron and Lake Erie has a thin freshwater aquifer overlain by an aquitard of Late Pleistocene clayey glaciolacustrine deposits and underlain by a thick Devonian shale aquitard. In a large area east of the St. Clair River, where the Quaternary aquitard is 30-50 m thick, groundwater of Pleistocene origin (identified by 18O and 2H signature) occurs in the aquifer and in the bottom part of the Quaternary aquitard. Numerous piezometer nests in the aquitard show a downward hydraulic gradient with depth. In some areas, the aquitard has downward gradients only in the upper part and upward gradient in the lower part, indicating a transient condition. The piezometer nests in the clayey aquitard also show an increase in Cl- concentration with depth. Long-term piezometer monitoring at two sites show a major shift in the aquitard hydraulic gradient since 1983 and a large rise in head in the underlying aquifer. Analyses of initial aquifer water levels, reported in well drilling records, indicate a large decline in the potentiometric surface of the aquifer between the 1940's and the 1970's followed by a recent rise in the surface in part of the region. This pattern is consistent with well drilling and water use records indicating that 7000 wells were installed in the aquifer in the three decades since 1940 and that groundwater use has greatly diminished in the past 10-15 years due to rural pipeline distribution of lake and river water. The hydraulic gradient in the aquitard is slowly adjusting to the rise in the aquifer potentiometric surface. One-dimensional solute transport modelling provides close matches to the vertical profiles of Cl- migrating upward from the aquifer since deglaciation, 15 000 - 18 000 years before present, by diffusion with little or no advection. The lack of advection indicates a near-neutral long-term hydraulic gradient. As the withdrawal rate of water from the aquifer continues to decline, it is expected that the hydraulic head in the aquitard in much of the area westward of the recharge area will continue to adjust for many decades.Key words: clay, aquitard, aquifer, water use, hydraulic gradient.
34
Christner, Brent C., Heather F. Lavender, Christina L. Davis, Erin E. Oliver, Sarah U. Neuhaus, Krista F. Myers, Birgit Hagedorn, Slawek M. Tulaczyk, Peter T. Doran e William C. Stone. "Microbial processes in the weathering crust aquifer of a temperate glacier". Cryosphere 12, n. 11 (26 novembre 2018): 3653–69. http://dx.doi.org/10.5194/tc-12-3653-2018.
Testo completoAbstract (sommario):
Abstract. Incident solar radiation absorbed within the ablation zone of glaciers generates a shallow perched aquifer and seasonal icebound microbial habitat. During the melt seasons of 2014 and 2015, borehole investigations were used to examine the physical, geochemical, and microbiological properties in the near-surface ice and aquifer of the temperate Matanuska Glacier (south-central Alaska). Based on temperature, solar forcing, and ice optical properties, the dissipation of shortwave radiation promoted internal melting and the formation of a weathering crust with a maximum depth of ∼2 m. Boreholes into the weathering crust provided access to water percolating through the porous ice. The water had low ion concentrations (4–12 µS cm−1), was aerobic (12 mg O2 L−1), contained 200 to 8300 cells mL−1, and harbored growing populations with estimated in situ generation times of 11 to 14 days. During the melt season, the upper 2 m of ice experienced at least 3 % of the surface photosynthetically active radiation flux and possessed a fractional water content as high as 10 %. Photosynthetic subsistence of biogeochemical reactions in the weathering crust ecosystem was supported by ex situ metabolic experiments and the presence of phototrophic taxa (cyanobacteria, golden and green algae) in the aquifer samples. Meltwater durations of ∼7.5 months coupled with the growth estimates imply biomass may increase by 4 orders of magnitude each year. Our results provide insight into how seasonal dynamics affect habitability of near-surface ice and microbial processes in a portion of the glacial biome poised to expand in extent with increasing global temperature and ablation season duration.
35
Lauber, U., W. Ufrecht e N. Goldscheider. "Spatially resolved information on karst conduit flow from in-cave dye tracing". Hydrology and Earth System Sciences 18, n. 2 (5 febbraio 2014): 435–45. http://dx.doi.org/10.5194/hess-18-435-2014.
Testo completoAbstract (sommario):
Abstract. Artificial tracers are powerful tools for investigating karst systems. Tracers are commonly injected into sinking streams or dolines, while springs serve as monitoring sites. The obtained flow and transport parameters represent mixed information from the vadose, epiphreatic and phreatic zones (that is, the aquifer remains a black box). Accessible active caves constitute valuable but underexploited natural laboratories to gain detailed insights into the hydrologic functioning of the aquifer. Two multi-tracer tests in the catchment of a major karst spring (Blautopf, Germany) with injections and monitoring in two associated water caves aimed at obtaining spatially and temporally resolved information on groundwater flow in different compartments of the system. Two tracers were injected into the caves to characterize the hydraulic connections between them and with the spring. Two injections at the land surface, far from the spring, aimed at resolving the aquifer's internal drainage structure. Tracer breakthrough curves were monitored by field fluorimeters in caves and at the spring. Results demonstrate the dendritic drainage structure of the aquifer. It was possible to obtain relevant flow and transport parameters for different sections of this system. The highest mean flow velocities (275 m h−1) were observed in the near-spring epiphreatic section (open-channel flow), while velocities in the phreatic zone (pressurized flow) were one order of magnitude lower. Determined conduit water volumes confirm results of water balances and hydrograph analyses. In conclusion, experiments and monitoring in caves can deliver spatially resolved information on karst aquifer heterogeneity and dynamics that cannot be obtained by traditional investigative methods.
36
Giudici, M., M. Manera e E. Romano. "The use of hydrological and geoelectrical data to fix the boundary conditions of a ground water flow model: a case study". Hydrology and Earth System Sciences 7, n. 3 (30 giugno 2003): 297–303. http://dx.doi.org/10.5194/hess-7-297-2003.
Testo completoAbstract (sommario):
Abstract. To assess whether the hydrometric level of an artificial lake in a quarry near Milan (Italy) could be assigned as a Dirichlet boundary condition for the phreatic aquifer in a fine scale groundwater flow model, hydrological measurements of piezometric head and rainfall rate time series have been analysed by spectral and statistical methods. The piezometric head close to the quarry lake proved to be well correlated with seasonal variations in the rainfall. Furthermore, geoelectrical tomography detected no semi-permeable layer between the phreatic aquifer and the lake, so the contact between surface and ground water is good. Finally, a time-varying prescribed head condition can be applied for ground water flow modelling. Keywords: ground water flow, boundary conditions, surface and ground water interactions, geoelectrical tomography, statistical analysis.
37
Ibarra-Olivares, Guadalupe, Raúl Miranda-Avilés, José A. Ramos-Leal, Janete Morán-Ramirez, María Jesús Puy-Alquiza, Yanmei Li, Edgar Ángeles-Moreno e Pooja Kshirsagar. "Hydrogeochemical Characterization of Groundwater at the Boundaries of Three Aquifers in Central México". Water 15, n. 22 (13 novembre 2023): 3948. http://dx.doi.org/10.3390/w15223948.
Testo completoAbstract (sommario):
This study investigates the natural hydrogeochemical mechanisms that govern groundwater chemistry at the margins of the Silao-Romita, Valle de León, and La Muralla aquifers in Mexico’s “Bajío Guanajuatense”. The wells of the La Muralla aquifer have temperatures ranging from 25 to 45 °C, while in the valleys, the temperatures range from 25 to 29 °C. In the Sierra de Guanajuato recharge zone, the thermal spring registers 95 °C. High Na concentrations (125 to 178 mg/L) are measured due to thermalism. One sample includes 316 mg/L of SO4, which is related to a potential gypsum zone. Three hydrogeochemical facies are identified (Ca-Mg HCO3, Na-Ca-HCO3, and Na-HCO3). The hydrogeochemical characterization and processes imply hydraulic linkage via regional thermal flows enhanced by faults and the mixing of local flow waters with intermediate flows. The isotopic results indicate that part of the groundwater volume has been exposed to local evaporation processes due to the presence of surface water bodies and irrigation returns. The highest isotopic enrichment is observed near or in the recharge regions. In contrast, the most depleted zones are in the valleys, where there is a more significant interaction with the rock and a longer residence time, implying a mixture of local water flows with deeper or intermediate flows, which, when combined with water geochemistry, indicates a connection between the aquifers studied. The Kruskal–Wallis variance tests, used to compare the differences between aquifers, show that the Valle de León aquifer has more significant differences with respect to the Silao-Romita and La Muralla aquifers. This study’s findings are essential for one of central Mexico’s most populous and economically active areas.
38
Husain, Muin M., John A. Cherry e Shaun K. Frape. "The persistence of a large stagnation zone in a developed regional aquifer, southwestern Ontario". Canadian Geotechnical Journal 41, n. 5 (1 settembre 2004): 943–58. http://dx.doi.org/10.1139/t04-040.
Testo completoAbstract (sommario):
An extensive groundwater zone of exceptionally negative δ18O (17.5 to 16.0) exists in a thin, regional, freshwater aquifer between Lake St. Clair and the southern shore of Lake Huron in southwestern Ontario. The zone occurs at the interface between the overlying thick Quaternary clay aquitard of glaciolacustrine origin and the underlying bedrock shale. This isotope signature, which is 7 more negative (lighter) than modern water, indicates a Late Pleistocene origin of the aquifer water. This zone occurs only where the Quaternary aquitard is greater than 35 m thick. In the Quaternary aquitard, the Pleistocene isotope signature extends upward from the aquifer and then has a gradational transition to signature resembling modern water (10) near the ground surface. This regional-scale study of the aquiferaquitard system indicates that the pattern of flow of the aquifer has allowed the persistence of the Pleistocene groundwater since the aquitard was deposited approximately 10 000 years before present. As part of the regional study, a two-dimensional groundwater flow model was used to assess the origin and persistence of the Pleistocene zone under natural conditions. The persistence of the Pleistocene zone was also assessed based on water budgets prepared from aquifer use history and aquiferaquitard parameters. Our study finds that the low yield and poor quality of groundwater in this zone have caused minimal use, resulting in the persistence of the Pleistocene groundwater since the beginning of major aquifer use in the 1940s.Key words: regional aquifer, aquitard, Pleistocene water, stagnation, aquifer use.
39
Slade, Raymond Maurice. "A recharge-discharge water budget and evaluation of water budgets for the Edwards Aquifer associated with Barton Springs". Texas Water Journal 8, n. 1 (27 giugno 2017): 42–56. http://dx.doi.org/10.21423/twj.v8i1.7020.
Testo completoAbstract (sommario):
The Barton Springs segment of the Edwards Aquifer represents a small, relatively independent part of the aquifer. Data for the sources of recharge and especially for discharge from the aquifer are well documented. Based on a 6-year water budget of surface recharge and surface discharge, the volumes match within 5%, which is within the potential error limits of the recharge and discharge values. Recharge volumes include increased runoff due to urbanization in the recharge area. A previous water budget based on an earlier period also displayed a balance between recharge and discharge volumes. Both budgets are based on slightly “wetter” than long-term mean recharge and discharge conditions, thus subsurface recharge from south of the aquifer segment, which is documented to occur during dry conditions, was an insignificant source of recharge during the budget periods. The recharge volumes are based on data from streamflow gaging stations operated by the U.S. Geological Survey. However, one of the stations (Bear Creek near Brodie Lane) was discontinued in 2010; this station is needed to calculate recharge volumes on Bear Creek and Little Bear Creek. Because of the discontinuance of the station, any calculations of recharge volumes after 2010 would contain substantial potential error. Citation: Slade RM, 2017. A recharge-discharge water budget and evaluation of water budgets for the Edwards Aquifer associated with Barton Springs. Texas Water Journal. 8(1):42-56. Available from: https://doi.org/10.21423/twj.v8i1.7020.
40
Trček, Branka, e Beno Mesarec. "Impact of the Hydroelectric Dam on Aquifer Recharge Processes in the Krško Field and the Vrbina Area: Evidence from Hydrogen and Oxygen Isotopes". Water 15, n. 3 (19 gennaio 2023): 412. http://dx.doi.org/10.3390/w15030412.
Testo completoAbstract (sommario):
The impact of the damming of the Sava river for the Brežice hydroelectric power plant on the rise of the groundwater level was studied in the intergranular aquifer of the Krško field and the Vrbina area, Slovenia. The study is based on the application of hydrogen and oxygen isotopes (18O, 2H and 3H). Parameters were determined for precipitation, surface water, and groundwater for periods before and after the filling of the accumulation basin, with the aim of evaluating the groundwater–surface water interaction and to elucidate the impact of the hydroelectric dam on aquifer recharge processes. The results show the proportions of the surface water component in groundwater sampled from four wells at high and low water conditions, separately for the period before and after the filling the accumulation basin. After filling the accumulation basin, the proportion of the Sava river component at high water conditions increased from 60% to 80% in the Brege and Drnovo wells (drinking water resources), from 50% to 80% in the Cerklje well and to almost 100% in the near-river NEK well. Combined with previous studies, the results provide important information about the direction of groundwater flow in the aquifer and improve the conceptual model of the study site.
41
Eastoe, Christopher, Barry Hibbs, Mercedes Merino e Jason Dadakis. "Origins of Sulfate in Groundwater and Surface Water of the Rio Grande Floodplain, Texas, USA and Chihuahua, Mexico". Hydrology 9, n. 6 (24 maggio 2022): 95. http://dx.doi.org/10.3390/hydrology9060095.
Testo completoAbstract (sommario):
Sulfate isotopes (δ34S, δ18OSO4) interpreted in conjunction with sulfate concentrations show that sulfate of both agricultural and geologic sources is present in groundwater and surface water in the Rio Grande flood plain within the Hueco Bolsón. From previous studies, water isotopes (δ2H, δ18O) in the study area indicate groundwater age relative to dam construction upstream. Surface water entering the Hueco Bolsón contains a mixture of soil-amendment sulfate and sulfate from deep-basin groundwater seeps at the terminus of Mesilla Valley. In the shallow Rio Grande alluvial aquifer within the Hueco Bolsón, ranges of δ34S in pre-dam (+2 to +9‰) and post-dam (0 to +6‰) groundwater overlap; the range for post-dam water coincides with common high-sulfate soil amendments used in the area. Most post-dam groundwater, including discharge into agricultural drains, has higher sulfate than pre-dam groundwater. In surface water downstream of Fabens, high-δ34S (>+10‰) sulfate, resembling Middle Permian gypsum, mixes with sulfate from upstream sources and agriculture. The high- δ34S sulfate probably represents discharge from the regional Hueco Bolsón aquifer. In surface water downstream of Fort Hancock, soil-amendment sulfate predominates, probably representing discharge from the Rio Grande alluvial aquifer near the basin terminus. The δ18OSO4 dataset is consistent with sulfate origins determined from the larger δ34S dataset.
42
Balia, Roberto, Enrico Gavaudò, Federica Ardau e Giorgio Ghiglieri. "Geophysical approach to the environmental study of a coastal plain". GEOPHYSICS 68, n. 5 (settembre 2003): 1446–59. http://dx.doi.org/10.1190/1.1620618.
Testo completoAbstract (sommario):
In the study of coastal plains affected by soil and water salination, a knowledge of several geological aspects, such as structural features, depth to basement, stratigraphy of sedimentary cover, relationships between the phreatic aquifer and underlying aquifers, and the latter's structure, is basic to gaining an adequate understanding of both the causes and possible evolution of salination. In this framework, geophysical techniques can play a very important role. To improve the available geophysical information about the Muravera coastal plain, Sardinia, Italy, which is affected by severe soil and water salination, previously acquired electrical resistivity, reflection seismic and gravity data have been reprocessed, and a new seismic reflection survey has been conducted. Moreover, in order to give better support to the geological and hydrogeological interpretation of geophysical data, three boreholes were drilled. Reprocessed electrical data indicate the presence of a wide, electrically homogeneous low‐resistivity zone associated with salination phenomena. Reprocessed reflection data provide useful information on the near‐surface stratigraphy. The combined interpretation of resistivity and seismic results, supported by one calibration borehole, elucidates the relationships between the phreatic aquifer and the underlying confined aquifer. A new seismic reflection survey gives information on the depth to, and structure of, the Paleozoic basement, as well as on stratigraphic conditions of Pleistocene‐Holocene sediments. Finally, the combined interpretation of seismic, gravity, and well data results in a geological section containing most of the information considered essential, such as the interface between Holocene alluvium and Pleistocene alluvium, the thickness of the latter, and the structure and composition of the Paleozoic basement. The work as a whole shows how the combined application of geophysical techniques can in this specific situation provide wide‐ranging and high‐quality information that is essential for the realistic mathematical modeling of aquifer contamination, and can enable the rational planning of exploratory drillings.
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D A, Ogwu, Molua O C, Ighodalo E.J e Edobor M. "Hydrogeophysical Investigation of Aquifer Layers in Nkporo, Ohafia Local Government Area". Journal of Energy Engineering and Thermodynamics, n. 24 (5 luglio 2022): 8–15. http://dx.doi.org/10.55529/jeet.24.8.15.
Testo completoAbstract (sommario):
Drilling a borehole in Nkporo area of Ohafia in Abia state without proper investigation may lead to wasting resources if water bearing formation is not achieved. This is because borehole drilling is very expensive. It is therefore necessary to carry out proper hydro-geophysical investigation in order to identify a good aquifer before borehole drilling. Electrical resistivity method has been chosen for the investigation of the water bearing formation. The use of Schlumberger array (Vertical Electrical Sounding (VES)) method of electrical resistivity was chosen based on the geology of the study area. This method was chosen because not only will it delineate the layers of the near surface aquifer but will also determine the thickness and depth to the aquifer. Five (5) vertical electrical soundings data were obtained from five (5) locations in the community using the Schlumberger array method. The investigations reveal that the area is mostly underlain shale. The formations are poor in aquifer materials. Borehole therefore, in the area should be drilled deep to depths ranging between 700 – 900m into sandstone as revealed in VES 3 and VES 4.
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Duckett, Kyle, Jeff Langman, John Bush, Erin Brooks, Pamela Dunlap e Jeffrey Welker. "Isotopic Discrimination of Aquifer Recharge Sources, Subsystem Connectivity and Flow Patterns in the South Fork Palouse River Basin, Idaho and Washington, USA". Hydrology 6, n. 1 (3 febbraio 2019): 15. http://dx.doi.org/10.3390/hydrology6010015.
Testo completoAbstract (sommario):
Groundwater studies in the South Fork Palouse River Basin have been unable to determine recharge sources, subsystem connectivity and flow patterns due to the discontinuity of pathways in the heterogeneous and anisotropic aquifers located in Columbia River flood basalts and interbedded sediments. Major ion, δ18O, δ2H, δ13C, δ34S and temperature for groundwater collected from 28 wells of varying depths indicate a primary recharge source dominated by snowmelt along the eastern basin margin. This recharge can be separated into two distinct sources—a deeper and relatively less altered snowmelt signal (−17.3‰ to −16.8‰ δ18O, −131‰ to −127‰ δ2H, −12.9‰ to −10‰ δ13C, 18–23 °C) and a more altered signal likely derived from a shallower mixture of snowmelt, precipitation and surface water (−16.1‰ to −15.5‰ δ18O, −121‰ to −117‰ δ2H, −15.9‰ to −12.9‰ δ13C, 12–19 °C). A mixing of the shallow and deep source waters is observed within the upper aquifer of the Grande Ronde Formation near Moscow, Idaho, which results in a homogenization of isotope ratios and geochemistry for groundwater at nearly any depth to the west of this mixing zone. This homogenized signal is prevalent in a likely primary productive zone of an intermediate depth in the overall aquifer system.
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Slimani, Rabia, Abdelhamid Guendouz, Fabienne Trolard, Adnane Souffi Moulla, Belhadj Hamdi-Aïssa e Guilhem Bourrié. "Identification of dominant hydrogeochemical processes for groundwaters in the Algerian Sahara supported by inverse modeling of chemical and isotopic data". Hydrology and Earth System Sciences 21, n. 3 (21 marzo 2017): 1669–91. http://dx.doi.org/10.5194/hess-21-1669-2017.
Testo completoAbstract (sommario):
Abstract. Unpublished chemical and isotopic data taken in November 1992 from the three major Saharan aquifers, namely the Continental Intercalaire (CI), the Complexe Terminal (CT) and the phreatic aquifer (Phr), were integrated with original samples in order to chemically and isotopically characterize the largest Saharan aquifer system and investigate the processes through which groundwaters acquire their mineralization. Instead of classical Debye–Hückel extended law, a specific interaction theory (SIT) model, recently incorporated in PHREEQC 3.0, was used. Inverse modeling of hydrochemical data constrained by isotopic data was used here to quantitatively assess the influence of geochemical processes: at depth, the dissolution of salts from the geological formations during upward leakage without evaporation explains the transitions from CI to CT and to a first end member, a cluster of Phr (cluster I); near the surface, the dissolution of salts from sabkhas by rainwater explains another cluster of Phr (cluster II). In every case, secondary precipitation of calcite occurs during dissolution. All Phr waters result from the mixing of these two clusters together with calcite precipitation and ion exchange processes. These processes are quantitatively assessed by the PHREEQC model. Globally, gypsum dissolution and calcite precipitation were found to act as a carbon sink.
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Kobierska, F., T. Jonas, J. Kirchner e S. M. Bernasconi. "Linking baseflow separation and groundwater storage dynamics in an alpine basin (Dammagletscher, Switzerland)". Hydrology and Earth System Sciences Discussions 11, n. 11 (3 novembre 2014): 12187–221. http://dx.doi.org/10.5194/hessd-11-12187-2014.
Testo completoAbstract (sommario):
Abstract. This study aims at understanding interactions between stream and aquifer in a glacierized alpine catchment. We specifically focused on a glacier forefield, for which continuous measurements of stream water electrical conductivity, discharge and depth to the water table were available over four consecutive years. Based on this dataset, we developed a two-component mixing model in which the groundwater component was modelled using measured groundwater levels. The aquifer actively contributing to stream flow was assumed to be a superposition of two linear storage units. Calibrating the model against measured total discharge yielded reliable sub-hourly estimates of discharge and insights into groundwater storage properties. We found that a near-surface aquifer with high hydraulic conductivity overlies a larger reservoir with longer response time. Analyzing the mass balance of infiltration into the groundwater reservoir against exfiltration into the stream provided results that were in line with previous findings at this catchment.
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Pryambodo, Dino Gunawan, Joko Pihantono, Reiner Arief Troa e Eko Triarso. "Identifikasi Akuifer Dangkal di Pulau Terdepan NKRI dengan Menggunakan Metode Geolistrik 2D: Studi Kasus Pulau Laut, Kab. Natuna". EKSPLORIUM 37, n. 1 (31 maggio 2016): 51. http://dx.doi.org/10.17146/eksplorium.2016.37.1.2667.
Testo completoAbstract (sommario):
Kebutuhan akan air bersih untuk menunjang aktivitas masyarakat di bidang perikanan di pulau terluar sangat diperlukan karena di lokasi tersebut kondisinya minim sumber air tawar. Penelitian geofisika dengan metode Geolistrik 2D telah dilakukan untuk mengidentifikasikan keberadaan akuifer di Pulau Laut, Kabupaten Natuna sebagai pulau terluar dari wilayah Negara Kesatuan Republik Indonesia (NKRI). Pengukuran di lapangan dengan enam lintasan geolistrik 2D menggunakan konfigurasi Wenner, bentangan kabel 160 meter, untuk mendapatkan kedalaman penetrasi 26,9 meter di bawah permukaan. Data tahanan jenis di Pulau Laut digunakan untuk mengidentifikasi keberadaan akuifer di daerah penelitian. Akuifer berada pada kedalaman yang bervariasi di dekat permukaan dengan kedalaman 2,5 – 13 m di jalur utara, jalur PDAM, dan jalur Air Paying; 12 – 26,9 m di jalur Kadur, jalur Air Bunga, dan jalur Air Paying. Nilai tahanan jenis untuk setiap akuifer bervariasi di setiap jalur. Nilainya berkisar antara 0,651 – 14 Ωm. Litologi penyusun akuifer adalah satuan batupasir di jalur Kadur, Air Bunga, Talaga Tasik dan Air Paying; batulanau di jalur PDAM; dan batugamping di jalur utara. The need for fresh water to support community activities in the field of fisheries on the frontier island is necessary because this location has minimal condition to the source of fresh water. Geophysical research with 2D geoelectrical methods conducted to identify the aquifers in the area of Pulau Laut, Natuna Regency as the frontier island of United Country of Republic Indonesia (NKRI). In field, measurement is using six 2D geoelectric lines with Wenner configuration and 160 m cable stretching to obtain 26.9 m sub-surface depth penetration. Resistivity data in Pulau Laut used to identify the aquifer presence in research area. Aquifers are located on varies depth near the surface with a depth of 2.5 – 13 m in north line, PDAM line, and Air Paying line; 12 – 26.9 m in Kadur line, Air Bunga line, and Air Paying line. Resistivity value for each aquifer varies for each line. They are ranging from 0.651 – 14 Ωm. Lithologies, composing the aquifer, are sandstone unit in Kadur, Air Bunga, Talaga Tasik, and Air Paying lines; silstone in PDAM line; and limestone in the north line.
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Chen, Jung Wei, Kuan Wei Chen, Jung Nan Chang, Sun Zone Lee e C. H. Lee. "Evaluation on the River Seepage under Groundwater Pumping near Riverside". Applied Mechanics and Materials 212-213 (ottobre 2012): 383–90. http://dx.doi.org/10.4028/www.scientific.net/amm.212-213.383.
Testo completoAbstract (sommario):
Abstract. Groundwater is to be pumping near the riverside could be induced recharge from the river surface and lateral aquifer layers, and could be reduced the negative effect on the aquifer. In this research, proposes the method of pumping groundwater from the Maoluo riverside and assesses the effect on the riverbank filtration in the middle of Taiwan. This research constructed the four analytical models using MODFLOW to identify the reliability of numerical model. Five groundwater pumping schemes based on the assessment on the effect of the Maoluo river seepage were implemented. For replace with the external water sources is 60,000 CMD, the ratio of river seepage to pumping is from 37.5% to 40.2%, and the groundwater radius of influence is from 290m to 470m. The research area is 700 m away from the residential area, none pumping schemes will thus affect the residential area.
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Steiakakis, Emmanouil, Dionysios Vavadakis e Ourania Mourkakou. "Groundwater Vulnerability and Delineation of Protection Zones in the Discharge Area of a Karstic Aquifer—Application in Agyia’s Karst System (Crete, Greece)". Water 15, n. 2 (5 gennaio 2023): 231. http://dx.doi.org/10.3390/w15020231.
Testo completoAbstract (sommario):
This work represents a contribution to the protection techniques of karst aquifers against groundwater pollution. The paper sets out the methodology being introduced for the protection of the karstic system that gives rise to five (5) major groups of springs and supplies fourteen (14) pumping wells near Agyia Chania (Crete, Greece). Starting from a geological and hydrogeological survey of the area, the work presents a vulnerability assessment of the karstic aquifer based on the application of three index-based methods (EPIK, PRESK and DRISTPI). The protection zones for the discharge area of the aquifer were delineated through an integrated geomorphological approach and groundwater flow modeling. At first, the risk of polluting substances migration from ground surface to groundwater was considered based on the spatial distribution of vulnerability. Following this, the vulnerability was evaluated in the saturated zone, where the attenuation mechanisms of contaminants were reducing due to the raised flow velocity. The groundwater flow and contaminant transport processes was considered using the MODFLOW code. Next, the data from the vulnerability mapping and the groundwater flow simulation were merged into an integrated assessment to delimit the protection zones for the water abstraction points. The vulnerability assessment outlines zones of high vulnerability in the SE part of the area, far away from the discharge zone of the aquifer and the water abstraction points. These zones are associated with an intensive infiltration process via carbonate formations. Protection Zone I was delineated 20 m around the water abstraction points, and it should be excluded from any anthropogenic activity. Protection Zone II coves part of the very high and high vulnerability zones defined by the DRISTPI method (located upwards of the water abstraction points), as well as an area downwards of springs and wells, where the flow path lines which demonstrate the subsurface travelling time of 50 days are projected to the ground surface. Protection Zone III extends outside Zone Ι and Zone ΙΙ, up to the limits of the hydrogeological or hydrological basin, whichever is larger. It includes the entire capture zone (i.e., the surface and underground catchment area) that feeds the water abstraction points. In this manner the protection zones include the entire contributing area to water abstraction points, not just the ground surface recharge zone.
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Ramachandran, Kumar, Bryan Tapp, Tayler Rigsby e Erin Lewallen. "Imaging of Fault and Fracture Controls in the Arbuckle-Simpson Aquifer, Southern Oklahoma, USA, through Electrical Resistivity Sounding and Tomography Methods". International Journal of Geophysics 2012 (2012): 1–10. http://dx.doi.org/10.1155/2012/184836.
Testo completoAbstract (sommario):
Arbuckle-Simpson aquifer in southern Oklahoma, USA, is a major source of water for industrial and municipal use. It is also a major source for spring-fed streams in the area. As part of an ongoing study to map and characterize the Arbuckle-Simpson aquifer, an electrical resistivity tomography (ERT) study and electrical resistivity sounding studies were conducted in Johnston County, Oklahoma, USA, to map the subsurface of a small area of the carbonate aquifer. The main aim of the study was to obtain constraints on the location of near surface faults and fractures and how they control groundwater flow in the study area. The interpreted resistivity section along an N-S profile indicates that the water table in the region is deepening to the south and probably bounded in the north by a south dipping fault. Inverse modeling of 2D electrical resistivity tomography (ERT) data acquired at two adjacent locations within the study area indicate shallow, fractured Arbuckle group rocks saturated with water adjacent to dry rocks. From electrical resistivity mapping results, it is inferred that the Mill Creek block in the Arbuckle-Simpson aquifer is an isolated system, interacting with the northern segment of a silicate-based aquifer through dissolution faults and fractures.