Geoscience Reference
In-Depth Information
aquifer. The saltwater was flushed out or stopped saltwater intrusion to
the aquifer. However, if the severe drought conditions (higher temperature,
lesser rainfall) occur in the delta, the water table is reduced due to higher
evapotranspiration and over pumping the ground water for irrigation and
domestic purposes. The saltwater intruded to the aquifer and freshwater
thickness reduced in the delta.
4. Summary and Conclusions
Mathematical and numerical models are useful to estimate subsurface water
and contamination discharge to coastal areas from point and non-point
source areas. Applications of two types of numerical models were presented
in this paper. As an example, a finite element model, considering open
boundary conditions for coasts and a sharp interface between freshwater
and saltwater was applied under steady-state conditions to the phreatic
aquifer for freshwater surplus and deficits at the coastline due to El Nino
effect. When recharges of saltwater occur at the coastline, essentially of
freshwater deficits, a hypothesis of mixing for the freshwater-saltwater tran-
sition zone allows the model to calculate the resulting seawater intrusion in
the aquifer. Hence, an adequate treatment and interpretation of the hydro-
geological data that are available for a coastal aquifer are of main concern
in satisfactorily applying the numerical model.
The results of the steady-state simulations showed reasonable calcula-
tions of the water table levels and the freshwater and saltwater thicknesses,
as well as, the extent of the interface and seawater intrusion into the aquifer
for the total discharges or recharges along the coastline. As a result of the
present hydrogeological simulations on the subsurface system, a consider-
able advance in seawater intrusion would be expected in the coastal water-
shed if the sea level rises due to climate change and El Nino effects.
References
1. A. G. Bobba, Mathematical models for saltwater intrusion in coastal
aquifers — literature review,
Water Resources Management
(1993a) 3-37.
2. H. J. Bokuniewicz, Groundwater seepage into Great South Bay, New York,
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3. I. Valiela, K. Foreman, M. LaMontagne, D. Hersh, J. Costa, Peckol DeMeo-
Anderson, C. D'Avanzo, M. Babione, C. Sham, J. Brawley and K. Lajyha,
Coupling of watersheds and coastal waters: Sources, and consequences of
nutrient enrichment in Waquoit Bay, Massachusetts,
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