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Modeling Lakebed Hydrogeological Properties Effects on Lake and Groundwater Interaction (Case Study: Lake Urmia)

Sheibani, Sorour | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53028 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ataie Ashtiani, Behzad
  7. Abstract:
  8. Lake Urmia water level fell dramatically from 2006 to 2014. Since then the declining trend of water level has stopped but the lake has remained in a critical situation. Moreover, Lake Urmia became supersaturated with total salinity averaging more than 350 g/l. Salt precipitation and dissolved materials brought by inflowing rivers have formed a layer of sediment with low hydraulic conductivity on the lakebed. We conducted a series of numerical simulation scenarios to study the groundwater flow pattern in the vicinity of the hypersaline Lake Urmia using COMSOL Multiphysics®. In the first step, we performed the simulations in steady-state conditions. Secondly, we simulated the lake level fall in 10 years at a rate of -35 cm/yr followed by a lake level rise at a rate of 35 cm/yr for another 10 years. The steady-state results demonstrate that decreasing sediment hydraulic conductivity layer and increasing its thickness lead to a less intense saltwater intrusion, with lower saltwater flux from the lake to the aquifer while changing aquifer hydraulic conductivity does not affect intrusion rate. As the lake level begins to fall, in cases with high sediment hydraulic conductivity, incoming saltwater from the lake decreases and reaches nearly zero values through the time. In all simulated cases, the saltwater toe retreats about 1.5 m during this period. As the lake level begins to rise after the falling period, the saltwater flux from the lake to the aquifer increases and finally reaches a value of nearly two times greater than steady-state results. In low sediment hydraulic conductivity cases, incoming saltwater from the lake to the aquifer remains negligible through both rising and falling scenarios. During the time that water level is rising the saltwater toe retreats about 10 m and the incremental effect of the rising level does not occur considerably
  9. Keywords:
  10. Seawater Intrusion ; Coastal Aquifer ; Urumieh Lake ; Surface Water and Groundwater Interaction ; Water Flow

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