Testing Alternative Conceptual Models of Seawater Intrusion in a Coastal Aquifer Using Computer Simulation, Southern California, USA

Two alternative conceptual models of the physical processes controlling seawater intrusion in a coastal basin in California, USA, were tested to identify a likely principal pathway for seawater intrusion. The conceptual models were tested by using a two-dimensional, finite-element groundwater flow a...

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Bibliographic Details
Published in:Hydrogeology journal 1997-03, Vol.5 (3), p.60-74
Main Author: Nishikawa, Tracy
Format: Article
Language:English
Subjects:
Aquifer systems
Aquifers
Coastal aquifers
Computational fluid dynamics
Fluid flow
Geophysics
Groundwater flow
Hydraulics
Hydrology
Intrusion
Mathematical models
Pathways
Saline water intrusion
Sea water
Seawater
Submarine canyons
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Summary:Two alternative conceptual models of the physical processes controlling seawater intrusion in a coastal basin in California, USA, were tested to identify a likely principal pathway for seawater intrusion. The conceptual models were tested by using a two-dimensional, finite-element groundwater flow and transport model. This pathway was identified by the conceptual model that best replicated the historical data. The numerical model was applied in cross section to a submarine canyon that is a main avenue for seawater to enter the aquifer system underlying the study area. Both models are characterized by a heterogeneous, layered, water-bearing aquifer. However, the first model is characterized by flat-lying aquifer layers and by a high value of hydraulic conductivity in the basal aquifer layer, which is thought to be a principal conduit for seawater intrusion. The second model is characterized by offshore folding, which was modeled as a very nearshore outcrop, thereby providing a shorter path for seawater to intrude. General conclusions are that: 1) the aquifer system is best modeled as a flat, heterogeneous, layered system; 2) relatively thin basal layers with relatively high values of hydraulic conductivity are the principal pathways for seawater intrusion; and 3) continuous clay layers of low hydraulic conductivity play an important role in controlling the movement of seawater.[PUBLICATION ABSTRACT]
ISSN:1431-2174
1435-0157
DOI:10.1007/s100400050116