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Investigating the Effects of Urmia Lake’s Causeway on Salinity Changes and Bed Changes Caused by Salt Deposition

Alavimoghadam, Mahya | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57358 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Tajrishy, Massoud
  7. Abstract:
  8. The aim of the current research is to investigate the effects of the Urmia Lake causeway on salinity changes and bed changes caused by salt deposition with the help of modeling using Mike3 Flow Model FM, in order to help the recovery of Urmia Lake. In recent years, the balance between available water resources and water consumption in the catchment area of Lake Urmia has been severely disrupted due to human factors such as the construction of dams on rivers and crossings in the lake and natural factors such as climate change. Lake Urmia is located in the northwest of Iran. The length of this lake is about 140 km and its width varies from 15 to 60 km, and its average depth has now reached less than 2 meters. Lake Urmia with an altitude of 1250 meters above sea level is the 20th largest lake in terms of size and the second hypersaline lake in the world. This lake is divided into two northern and southern parts by a causeway in 1368. The two parts of the lake were connected through a 1,250-meter-long opening, which may have a significant effect on flow and salinity regimes. Some researchers considered the decrease in water flow and disturbance in the sedimentation process and flow circulation pattern in Lake Urmia to be caused by transitory effects; But some other researchers claimed that the effect of the causeway on salinity distribution is negligible. The first step in identifying factors affecting the condition and quality of the lake is to check the flow pattern. The construction of the causeway may be a factor in increasing the salinity of the lake and the difference in salinity concentration in the northern and southern parts of the lake, which can lead to side effects on the Artemia population, the rate of evaporation and the ecosystem of the lake; Therefore, studying the flow pattern and salinity distribution in the lake is inevitable. Therefore, in this research, a hydrodynamic model was developed first, and then with the help of this hydrodynamic model, changes in salinity, density, and changes in the lake bed due to salt deposits in three scenarios: 1. The existence of a causeway with an opening (the current conditions of the lake) 2. The absence of causeway 3. The presence of a causeway with two openings has been investigated. A detailed examination of the developed model showed that in the first model, which was developed from 2013 to 2014, there were no significant changes in salinity and density due to the different scenarios examined in this research, and up to 95% matching in the parts far from the crossing and 80% matching It was observed in the points near the intersection for these two parameters in the presented scenarios. But these scenarios have changed the flow pattern around the causeway. By using the second model, which was developed for 5 years from 2013 to 2018 with the aim of investigating the bed changes caused by salt deposits, it was concluded that different scenarios have caused bed changes around the causeway, but the changes in places far from the causeway not much happens from these scenarios. So that around the crossing in the condition of no crossing, there was about 0.5 meter difference in the total bed level changes compared to the condition of the crossing with one opening, and this difference was in the form of an increase compared to the initial conditions, but in the condition of the crossing with two openings, the difference was about 1 meter and this difference was a reduction compared to the initial conditions
  9. Keywords:
  10. Water Salinity Simulation ; Mike 3 Flow Model ; Evaporation ; Bed Level Change ; Bed Level Change ; Urmia Lake’s Causeway

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