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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 |
Type |
Journal Article |
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Year |
2010 |
Publication |
Hydrogeology Journal |
Abbreviated Journal |
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Volume |
18 |
Issue |
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Pages |
131-145 |
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Keywords |
Coastal aquifers; Inverse modelling; Numerical modeling |
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Abstract |
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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Address |
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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Publisher |
IAH |
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Springer |
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Language |
English |
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ISSN |
1431- 2174 (online: 1435-0157) |
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Area |
'Hydrogeology'; 'groundwater modelling' |
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Approved  |
yes |
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Call Number |
MGRE @ redha.menani @ |
Serial |
51 |
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Author |
Siarkos, I.; Latinopoulos, P. |
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Title |
Modeling seawater intrusion in overexploited aquifers in the absence of sufficient data: application to the aquifer of Nea Moudania, northern Greece |
Type |
Journal Article |
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Year |
2016 |
Publication |
Hydrogeology Journal |
Abbreviated Journal |
Hydrogeology J. |
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Volume |
24 |
Issue |
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Pages |
2123–2141 |
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Keywords |
Groundwater flow, Seawater intrusion, Numerical modeling, Greece, Sensitivity analysis |
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Abstract |
In many coastal areas, overexploitation of groundwater resources has led both to the quantitative degradation of local aquifers and the deterioration of groundwater quality due to seawater intrusion. To investigate the behavior of coastal aquifers under these conditions, numerical modeling is usually implemented; however, the proper implementation of numerical models requires a large amount of data, which are often not available due to the time-consuming and costly process of obtaining them. In the present study, the investigation of the behavior of coastal aquifers under the lack of adequate data is
attempted by developing a methodological framework consisting of a series of numerical simulations: a steady-state, a false-transient and a transient simulation. The sequence and the connection between these simulations constitute the backbone of the whole procedure aimed at adjusting the various
model parameters, as well as obtaining the initial conditions for the transient simulation. The validity of the proposed methodology is tested through evaluation of the model calibration procedure and the estimation of the simulation errors (mean error, mean absolute error, root mean square error, mean relative error) using the case of Nea Moudania basin, northern Greece. Furthermore, a sensitivity analysis is performed in order to minimize the error estimates and thus to maximize the reliability of the models. The results of the whole procedure affirm the proper implementation of the developed methodology under specific conditions and assumptions due to the lack of sufficient data, while they give a clear picture of the aquifer’s quantitative and qualitative status. |
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Address |
Ilias Siarkos: isiarkos@civil.auth.gr; Pericles Latinopoulos latin@civil.auth.gr |
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Corporate Author |
School of Civil Engineering, Aristotle University of Thessaloniki, GR54124 Thessaloniki, Greece |
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IAH |
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Springer |
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English |
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ISSN |
1431-2174 |
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Area |
Hydrogeology; groundwater modelling, sea water intrusion |
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Approved |
yes |
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Call Number |
MGRE @ redha.menani @ |
Serial |
52 |
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Author |
Hanshaw, B.B.; Back, W. |
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Title |
Major geochemical processes in the evolution of carbonate—Aquifer systems |
Type |
Journal Article |
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Year |
1979 |
Publication |
Journal of Hydrology |
Abbreviated Journal |
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Volume |
43 |
Issue |
1 |
Pages |
287-312 |
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Abstract |
As a result of recent advances by carbonate petrologists and geochemists, hydrologists are provided with new insights into the origin and explanation of many aquifer characteristics and hydrologic phenomena. Some major advances include the recognition that: (1) most carbonate sediments are of biological origin; (2) they have a strong bimodal size-distribution; and (3) they originate in warm shallow seas. Although near-surface ocean water is oversaturated with respect to calcite, aragonite, dolomite and magnesite, the magnesium-hydration barrier effectively prevents either the organic or inorganic formation of dolomite and magnesite. Therefore, calcareous plants and animals produce only calcite and aragonite in hard parts of their bodies. Most carbonate aquifers that are composed of sand-size material have a high initial porosity; the sand grains that formed these aquifers originated primarily as small shells, broken shell fragments of larger invertebrates, or as chemically precipitated oolites. Carbonate rocks that originated as fine-grained muds were initially composed primarily of aragonite needles precipitated by algae and have extremely low permeability that requires fracturing and dissolution to develop into aquifers. Upon first emergence, most sand beds and reefs are good aquifers; on the other hand, the clay-sized carbonate material initially has high porosity but low permeability, a poor aquifer property. Without early fracture development in response to influences of tectonic activity these calcilutites would not begin to develop into aquifers. As a result of selective dissolution, inversion of the metastable aragonite to calcite, and recrystallization, the porosity is collected into larger void spaces, which may not change the overall porosity, but greatly increases permeability. Another major process which redistributes porosity and permeability in carbonates is dolomitization, which occurs in a variety of environments. These environments include back-reefs, where reflux dolomites may form, highly alkaline, on-shore and continental lakes, and sabkha flats; these dolomites are typically associated with evaporite minerals. However, these processes cannot account for most of the regionally extensive dolomites in the geologic record. A major environment of regional dolomitization is in the mixing zone (zone of dispersion) where profound changes in mineralogy and redistribution of porosity and permeability occur from the time of early emergence and continuing through the time when the rocks are well-developed aquifers. The reactions and processes, in response to mixing waters of differing chemical composition, include dissolution and precipitation of carbonate minerals in addition to dolomitization. An important control on permeability distribution in a mature aquifer system is the solution of dolomite with concomitant precipitation of calcite in response to gypsum dissolution (dedolomitization). Predictive models developed by mass-transfer calculations demonstrate the controlling reactions in aquifer systems through the constraints of mass balance and chemical equilibrium. An understanding of the origin, chemistry, mineralogy and environments of deposition and accumulation of carbonate minerals together with a comprehension of diagenetic processes that convert the sediments to rocks and geochemical, tectonic and hydrologic phenomena that create voids are important to hydrologists. With this knowledge, hydrologists are better able to predict porosity and permeability distribution in order to manage efficiently a carbonate—aquifer system. |
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0022-1694 |
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Call Number |
THL @ christoph.kuells @ Hanshaw1979 |
Serial |
26 |
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Author |
Hanshaw, B.B.; Back, W. |
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Title |
Deciphering hydrological systems by means of geochemical processes |
Type |
Journal Article |
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Year |
1985 |
Publication |
Hydrological Sciences Journal |
Abbreviated Journal |
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Volume |
30 |
Issue |
2 |
Pages |
257-271 |
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Abstract |
The distribution of permeability and chemical character of groundwater in carbonate aquifers is significantly influenced by the many diagenetic processes
and reactions that occur in the early development of these rocks. Many of these diagenetic processes occur in the transition zone formed as the carbonate sediments emerge from the marine environment and become fresh-water aquifers. Analyses of trace elements and isotopes
indicate that calcite cements and dolomites are formed in this groundwater mixing zone. Reverse reactions such as mineral dissolution and dedolomitization occur in carbonate aquifer systems. The geochemical reactivity of the fresh-water/salt-water mixing zone results from the nonlinearity of geochemical parameters as a function of ionic strength and causes extensive dissolution in coastal carbonate rocks. Interpretation of geochemical reactions and isotopic composition of groundwater provides a method to determine hydrological parameters
such as porosity, hydraulic conductivity, and groundwater flow rates. This geochemical method is largely independent of the more conventional approach of determining these parameters by an evaluation of physical properties of aquifer systems. |
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ISSN |
0262-6667 |
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THL @ christoph.kuells @ Hanshaw1985 |
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25 |
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Author |
Han, D.; Post, V.E.A.; Song, X. |
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Title |
Groundwater salinization processes and reversibility of seawater intrusion in coastal carbonate aquifers |
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Journal Article |
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Year |
2015 |
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Journal of Hydrology |
Abbreviated Journal |
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Volume |
531 |
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Pages |
1067-1080 |
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Abstract |
Seawater intrusion (SWI) has led to salinization of fresh groundwater reserves in coastal areas worldwide and has forced the closure of water supply wells. There is a paucity of well-documented studies that report on the reversal of SWI after the closure of a well field. This study presents data from the coastal carbonate aquifer in northeast China, where large-scale extraction has ceased since 2001 after salinization of the main well field. The physical flow and concomitant hydrogeochemical processes were investigated by analyzing water level and geochemical data, including major ion chemistry and stable water isotope data. Seasonal water table and salinity fluctuations, as well as changes of δ2H–δ18O values of groundwater between the wet and dry season, suggest local meteoric recharge with a pronounced seasonal regime. Historical monitoring testifies of the reversibility of SWI in the carbonate aquifer, as evidenced by a decrease of the Cl− concentrations in groundwater following restrictions on groundwater abstraction. This is attributed to the rapid flushing in this system where flow occurs preferentially along karst conduits, fractures and fault zones. The partially positive correlation between δ18O values and TDS concentrations of groundwater, as well as high NO3− concentrations (\textgreater39mg/L), suggest that irrigation return flow is a significant recharge component. Therefore, the present-day elevated salinities are more likely due to agricultural activities rather than SWI. Nevertheless, seawater mixing with fresh groundwater cannot be ruled out in particular where formerly intruded seawater may still reside in immobile zones of the carbonate aquifer. The massive expansion of fish farming in seawater ponds in the coastal zone poses a new risk of salinization. Cation exchange, carbonate dissolution, and fertilizer application are the dominant processes further modifying the groundwater composition, which is investigated quantitatively using hydrogeochemical models. |
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Elsevier |
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ISSN |
0022-1694 |
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THL @ christoph.kuells @ Han2015 |
Serial |
24 |
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