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Development of a Hydrodynamic and Water Quality Model of Lake Urmia

Chamanmotlagh, Fatemeh | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54808 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Safaie, Ammar
  7. Abstract:
  8. Due to anthropogenic activities and climate change, Lake Urmia, one of the largest hypersaline lakes, is exposed to desiccating. The increase in salinity in this lake up to more than 400 p.s.u has endangered the ecology of this lake. In this study, a three-dimensional, unstructured grid and finite volume model FVCOM has been developed to investigate Lake Urmia's hydrodynamics, salinity, and water temperature over the year 2016. Some of the model inputs were lake bathymetry, meteorological data (including air temperature and pressure, wind speed and direction, short-wave and longwave radiation), precipitation, evaporation, river flux, salinity, and temperature. The model was calibrated simultaneously for salinity, water temperature, and velocity employing six stations' field data. After validating the model with the assistance of salinity, water level, and temperature, the model has accurately predicted flow regime, salinity, temperature, and water level fluctuations. Salinity in the lake was affected by the rivers' salinity, precipitation, and dissolution rate of minerals species. Without considering the precipitation and dissolution of the modeled salinity is on average 38% lower than the observed salinity of the lake. The salinity in the northern part of the lake was on average 59 p.s.u higher than the southern part's. Additionally, in summer, a weak thermal layering occurred in the lake.Furthermore, the PHREEQC inverse modeling was implemented to obtain minerals species' precipitation and dissolution rates. This model's results indicate that the sedimentation and dissolution of minerals had a significant effect on the salinity levels of the lake. Although brine discharges of rivers to the lake increased the lake's salinity, the lake's elevated salinity was dominantly caused by the salt precipitation/dissolution processes. In order to obtain the precipitation and dissolution rates of minerals species, temperature, density, pH, the concentration of sodium, potassium, calcium, magnesium, chlorine, bicarbonate, and sulfate in Lake Urmia were used as the PHREEQC inverse model's inputs. The Lake Urmia brine was classified as Na-Mg-Cl- (SO4) in February 2016. However, in December 2016, Lake Urmia brine was classified as Mg-Na-Cl-(SO4). In 2016 aragonite and anhydrite were supersaturated; halite was saturated; kieserite and sylvite were unsaturated in the lake. The annual precipitation and dissolution rate of minerals species was 0.018 p.s.u/hr (Salts dissolved in the lake at this rate)
  9. Keywords:
  10. Urumieh Lake ; Salinity ; Hydrodynamical Properties ; PHREEQC Software ; Finite Volume Ocean Comuntty Model (FVCOM) ; Hydrogeochemical Behavior ; Numerical Modeling

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