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Numerical Simulation of Seawater Intrusion in a Well-Developed Costal Karstaquifer by Using VDFST-CFP Model

Title: Numerical Simulation of Seawater Intrusion in a Well-Developed Costal Karstaquifer by Using VDFST-CFP Model.
Name(s): Xu, Zhongyuan, author
Hu, Bill X., professor directing thesis
Wang, Yang (Professor of Earth, Ocean and Atmospheric Science), committee member
Kish, Stephen A., committee member
Ye, Ming (Professor of scientific computing), committee member
Florida State University, degree granting institution
College of Arts and Sciences, degree granting college
Department of Earth, Ocean, and Atmospheric Science, degree granting department
Type of Resource: text
Genre: Text
Master Thesis
Issuance: monographic
Date Issued: 2017
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
online resource
Extent: 1 online resource (66 pages)
Language(s): English
Abstract/Description: Well-developed karst aquifers contain high permeability limestone matrix and much higher conductive conduits, this dual porosity system behaves totally different from other kinds of aquifers and becomes a challenging task for modern hydrogeological study. High permeable conduit system provides idea pipes for contaminant transporting in rapid flowing groundwater, this effect may cause wide range pollution in a short time. One of these serious problems is seawater intrusion. Seawater intrusion has been found in many coastal aquifers, produced contaminated fresh groundwater resources and induced ecosystem problems. Seawater intrusion in a well-developed karst aquifer such as Woodville Karst Plain (WKP) is simulated by Dr. Zexuan Xu (Xu and Hu, 2017a), he developed a new model VDFST-CFP (Variable-Density Flow and Solute Transport - Conduit Flow Process) which considers the variable density flow in dual porosity system. VDFST-CFP provides an accurate simulation of seawater intrusion in a coastal karst aquifer with conduit networks. It couples the variable density flow field and the density function of salinity in the porous medium and non-laminar groundwater flow within karst conduits. Currently, the VDFST-CFP model is used to simulate seawater intrusion condition at a synthetic level, the present numerical simulation only considered the idea circumstance that is one conduit in a 2D model, and data analyses mainly focused on the horizontal source. In this study, an improvement of VDFST-CFP will concentrate on the vertical source model in the WKP, the roughness of conduit wall and multiple pipes will be considered. Two improvement are implemented in the new model: (1) multi-conduit networks in the domain; (2) micro- and macro-structures on the conduit wall (conduit wall roughness). The simulation results show that dual-pipe system produced a larger contaminant plumes than single-pipe system. Meanwhile, rougher micro-structures and more macro-structures on conduit wall slow down the velocity of seawater intrusion in conduit system, however, have a limited affect salinity distribution in the matrix. In addition, local sensitivity analysis and global sensitivity analysis of seven parameters (conductivity, diameter, dispersivity, exchange permeability between conduit and matrix, effective porosity, mean roughness height and specific storage) are conducted in this study. Sensitivity results indicate that conductivity, diameter and porosity are more important to head and salinity distribution simulations than other four parameters. Diameter is the most important parameter to the conduit simulation, while matrix simulations is more sensitive to effective porosity. Furthermore, scenarios study about variation of boundary conditions is conducted, the result shows that a decreasing of salinity at submarine spring or a decreasing on sea level moves seawater intrusion backward both in conduit and matrix, while the intrusion in conduit and matrix have different sensitivities to the change of boundary conditions.
Identifier: FSU_SUMMER2017_Xu_fsu_0071N_13953 (IID)
Submitted Note: A Thesis submitted to the Department of Earth, Ocean and Atmosphere Science in partial fulfillment of the Master of Science.
Degree Awarded: Summer Semester 2017.
Date of Defense: June 1, 2017.
Keywords: coastal karst aquifer, Seawater intrusion, Sensitivity analysis, VDFST-CFP
Bibliography Note: Includes bibliographical references.
Advisory Committee: Xiaolong Hu, Professor Directing Thesis; Yang Wang, Committee Member; Stephen Kish, Committee Member; Ming Ye, Committee Member.
Subject(s): Hydrology
Persistent Link to This Record:
Owner Institution: FSU

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Xu, Z. (2017). Numerical Simulation of Seawater Intrusion in a Well-Developed Costal Karstaquifer by Using VDFST-CFP Model. Retrieved from