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| Titel |
Numerical modeling for evaluation of SGD fluxes constrained by radon-derived assessments |
| VerfasserIn |
Natasha Dimova, John Ellis, Geoffrey Tick, Chunmiao Zheng |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088910
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| Publikation (Nr.) |
 EGU/EGU2014-3086.pdf |
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| Zusammenfassung |
| It has been recognized that submarine groundwater discharge (SGD) may be one of the
principal mechanisms for delivering nutrients to surface water bodies. A multifaceted study
of the coastal aquifer system of Gulf Shores, Alabama was conducted to assess SGD fluxes
and associated nutrient loading to coastal areas. A three-dimensional density-dependent
numerical groundwater model was utilized and combined with field-based radon (222Rn,
t1-2=3.82 d) isotopic tracer techniques. Two model-based SGD estimation approaches were
developed to determine localized and entire-shoreline SGD fluxes. Both model
estimations for the surficial aquifer system were calibrated using 222Rn-derived
groundwater seepages to Lake Shelby, a groundwater-fed lake located within the
study area. To constrain the groundwater end-member in the model estimations, 50
groundwater samples from 32 wells in the study area representing all three aquifer units
were collected. The radon concentrations in groundwater from the uppermost two
regional aquifer units (A1 and A2) were statistically identical, an indication for
direct connection between these two aquifer units. Groundwater seepage calculated
through the radon mass-balance model resulted in a maximum groundwater flux
to Lake Shelby of 18.3 cm/day for these units, which was used to calibrate the
numerical model for the surficial aquifer system. Final shoreline seepage fluxes of 6.4
and 8.6-cm/day were obtained from the multi-cell and shoreface numerical model
approaches, respectively. The two model-based SGD estimation approaches displayed a
reasonable agreement with the radon-derived methods and provided an effective
approximation technique that can be inexpensively applied in other similar shoreline areas. |
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