The New Jersey Institute of Technology's
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Title:	Physical controls on water flow and solute transport in coastal aquifers
Author:	Geng, Xiaolong
View Online:	njit-etd2014-046 (xvii, 91 pages ~ 2.9 MB pdf)
Department:	Department of Civil and Environmental Engineering
Degree:	Doctor of Philosophy
Program:	Environmental Engineering
Document Type:	Dissertation
Advisory Committee:	Boufadel, Michel (Committee chair) Jackson, Nancy L. (Committee member) Axe, Lisa (Committee member) Dresnack, Robert (Committee member) Zhang, Wen (Committee member)
Date:	2014-05
Keywords:	Waves Evaporation Coastal hydrology Flow-averaged approach Subsurface solute transport Ground water flow
Availability:	Unrestricted
Abstract:	Groundwater flow and associated subsurface solute fates have a significant impact on the structure and productivity of near-shore coastal ecosystems. For proper assessment and management of these coastal groundwater resources, it is quite essential to investigate the key factors (tides, waves, evaporation, and freshwater recharge etc.) affecting coastal groundwater systems. The main objective of this study is to examine and quantify two important physical control factors, oceanic waves and evaporation, on the groundwater flow and solute transport in near-shore aquifers. For the investigation of wave effects, a Computational Fluid Dynamics (CFD) modeling tool, Fluent, is used to simulate wave- induced sea level oscillations. A flow-averaged approach is developed to generalize wave motions acting onto the beach for the sake of the feasibility of numerical computation. A two-dimensional numerical model MA RU N is used to simulate variably saturated, variable density groundwater flow and subsurface solute transport in coastal aquifers. To investigate evaporation effects, a classic bulk aerodynamic formulation is adopted as a module to the model MARUN for simulating groundwater flow and subsurface solute transport in bare saline soils subjected to transient evaporation. The simulation results reveal that these two factors significantly impact beach hydrodynamics. Wave forcing induces pore water circulations in the swash zone of the near-shore aquifers; wave forcing also modifies the pathways of solute transport in the beach prior to discharge into the ocean, and subsequently impacts plume’s residence time, migration speed, discharge location, and discharge rate. The evaporation decreases the moisture at shallow layer of the beach and subsequently impacts the subsurface salinity distribution.