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Author |
Sarker, M.M.R.; Van Camp, M.; Islam, M.; Ahmed, N.; Walraevens, K. |
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Title |
Hydrochemistry in coastal aquifer of southwest Bangladesh : origin of salinity |
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Journal Article |
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Year |
2018 |
Publication |
Environmental Earth Sciences |
Abbreviated Journal |
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Volume |
77 |
Issue |
2 |
Pages |
20 |
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Keywords |
Hydrochemistry,Stable isotope,Seawater intrusion,Coastal aquifer,Bangladesh,DAR-ES-SALAAM,SEAWATER INTRUSION,DELTA PLAIN,GROUNDWATER,DRINKING,TANZANIA,DROUGHT,COMPLEX |
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Abstract |
In the coastal region of Bangladesh, groundwater is mainly used for domestic and agricultural purposes, but salinization of many groundwater resources limits its suitability for human consumption and practical application. This paper reports the results of a study that has mapped the salinity distribution in different aquifer layers up to a depth of 300 m in a region bordering the Bay of Bengal based on the main hydrochemistry and has investigated the origin of the salinity using Cl/Br ratios of the samples. The subsurface consists of a sequence of deltaic sediments with an alternation of more sandy and clayey sections in which several aquifer layers can be recognized. The main hydrochemistry shows different main water types in the different aquifers, indicating varying stages of freshening or salinization processes. The most freshwater, soft NaHCO3-type water with Cl concentrations mostly below 100 mg/l, is found in the deepest aquifer at 200-300 m below ground level (b.g.l.), in which the fresh/saltwater interface is pushed far to the south. Salinity is a main problem in the shallow aquifer systems, where Cl concentrations rise to nearly 8000 mg/l and the groundwater is mostly brackish NaCl water. Investigation of the Cl/Br ratios has shown that the source of the salinity in the deep aquifer is mixing with old connate seawater and that the saline waters in the more shallow aquifers do not originate from old connate water or direct seawater intrusion, but are derived from the dissolution of evaporite salts. These must have been formed in a tidal flat under influence of a strong seasonal precipitation pattern. Long dry seasons with high evaporation rates have evaporated seawater from inundated gullies and depressions, leading to salt precipitation, while subsequent heavy monsoon rains have dissolved the formed salts, and the solution has infiltrated in the subsoil, recharging groundwater. |
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1866-6280 |
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THL @ christoph.kuells @ Sarker2018 |
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194 |
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Author |
Jesús Carrera, Juan J. Hidalgo, Luit J. Slooten, Enric Vázquez-Suñé |
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Title |
Computational and conceptual issues in the calibration of seawater intrusion models |
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Journal Article |
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Year |
2010 |
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Hydrogeology Journal |
Abbreviated Journal |
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18 |
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131-145 |
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Keywords |
Coastal aquifers; Inverse modelling; Numerical modeling |
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The inverse problem of seawater intrusion(SWI) is reviewed. It represents a challenge because of both conceptual and computational difficulties and because coastal aquifer models display many singularities:(1) head measurements need to be complemented with density information; (2) salinity concentration data are
very sensitive to flow within the borehole. Data problems can be reduced by incorporating the measurement process within model calibration; (3) SWI models are extremely sensitive to aquifer bottom topography; (4) the initial conditions may be far from steady state and depend on the location and type of sea-aquifer connection. Problems with aquifer geometry and initial conditions can be addressed by parameterization, which allows for modification during inversion. The four sets of difficulties can be partly overcome by using tidal response and electrical conductivity data, which are highly informative and
provide extensive coverage. Still, SWI inversion is extremely demanding from a computation point of view. Computational improvements are discussed. |
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J. Carrera : J. J. Hidalgo ()) : L. J. Slooten : E. Vázquez-Suñé, Spain e-mail: juan.hidalgo@upc.edu |
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Corporate Author |
Institute of Environmental Ass Institute of Environmental Assessment and Water Research (IDAEA), Spanish National Research Council (CSIC), Jordi Girona 18, 08034 Barcelona, e-mail: juan.hidalgo@upc.edu |
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IAH |
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Springer |
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English |
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1431- 2174 (online: 1435-0157) |
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'Hydrogeology'; 'groundwater modelling' |
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yes |
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MGRE @ redha.menani @ |
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51 |
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