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Effect of Sea Level Rise and Aquifer Characteristics on Seawater Intrusion in Coastal Aquifers

Mahmoudzadeh, Davood | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45174 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ataie Ashtiani, Behzad
  7. Abstract:
  8. Approximately, 60 percent of the world's populations are living at the distance of 60 kilometers of the coasts. In coastal zones, coastal aquifers are the most important resources of the available freshwater while expected that the short-term or long-term impacts of the climate changes threat such aquifers. In general, it is predicted that climate changes e.g. sea-level rise (SLR) cause to increase seawater intrusion (SWI) in the coastal aquifers. In this study, both continental and island coastal aquifers are considered. The objective of this research is the investigation of SWI behavior occurred in the coastal aquifers due to climatic change parameters and aquifer properties. For evaluation of the selected procedure in this study, a hypothetical example of a confined aquifer is considered based on previous studies and simulated using a numerical model, SUTRA. Therefore, the obtained results are evaluated.. The results obtained for this confined coastal aquifers show that, the SLR will not affect the steady-state salt wedge on confined aquifers, but considering transient condition, confined-flow simulations show a self-reversal mechanism due to groundwater system response to these changes and occurred to reach equilibrium. At the early time, SWI reached the maximum value, and then progress gradually returns to its initial state. For unconfined aquifer, recharge rate variations, land surface inundation (LSI) and beach slope of the coastal aquifer impacts are considered as well as SLR impacts. Due to the limitations of the analytical solutions, the numerical simulation is used to evaluate the abovementioned factors, The results indicated that a major effect of the beach slope and LSI often ignored as a simplifying assumption. The results of this section can be applied to real samples of the coastal aquifers. Such aquifer-behavior analyses can be really helpful and useful for further explorations. In the next part of this study, the investigation on the fresh groundwater lenses (FGLs) of the small islands is discussed, using the analytical and numerical solutions. The application of the novel analytical model to estimate the thickness and volume of FGL under the influence of climate change parameters and aquifer properties is focused. Furthermore, numerical modeling is applied to extend the analysis to consider dispersion effects and to confirm comparable results for both cases. LSI due to SLR has a significant impact on FGLs, although other parameters such as recharge rate, aquifer thickness and hydraulic conductivity impacts can be greater than the SLR impact on the volume of FGLs. For further investigation, a case study of Kish Island using the two-dimensional (2D) and three-dimensional (3D) models is conducted. It is provided the qualitative estimates for the expected SWI to the FGL and predicted extend of SLR, LSI, and recharge rate changes. The results demonstrate: (1) LSI impact is the major pressure of SLR influence on the FGL in small islands; especially in low-topography ones and reason to a thinner and flatter FGL shape by higher SLRs. (2) the rate of recharge variation is more important factor in the FGL in comparison to estimated SLR rates without LSI impact. (3) The simulations emphasizes that the climate change impacts on the FGL are long-term and can be far reaching under the Kish Island’s aquifer framework; and (4) The comparative analysis of 2D and 3D results exhibits that the obtained results from both 2D and 3D models are comparable and consistent whereas 3D models can be identify the more accurate results
  9. Keywords:
  10. Numerical Modeling ; Kish Island ; Sea Water Intrusion ; Climate Change ; Analytical Solution ; Aquifer Geometry

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