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Evaluation of Water Quality of Anzali Lagoon by Developing a Numerical Model

Saghafian, Mariam | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54093 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Safaie, Ammar
  7. Abstract:
  8. Wetlands are valuable ecosystems that have a wide variety of functions to protect biodiversity, natural, economic and social values. Hydrological changes and nutrient enrichment, resulting from population growth, economic development and climate change are threatening the wetlands. Recently, assessing spatial and temporal variations of water quality has become an important aspect of the physical and chemical characterization of aquatic environments. Anzali wetland is one of the international wetlands in Iran, located in the southern part of the Caspian Sea in Gilan province. This wetland has been exposed to many pollution sources including agricultural, industrial, and municipal wastewater that endanger its water quality. In order to simulate physical, chemical and biological processes in the Anzali lagoon, a fully coupled biophysical model of Anzali lagoon is developed based on three-dimensional, unstructured grid, Finite-Volume Community Ocean Model (FVCOM). Dynamics of water quality parameters are modeled using EPA Water Analysis Simulation Program (WASP5). This water quality model consists of dissolved oxygen budget, nutrient cycling, and phytoplankton biomass and is coupled with FVCOM hydrodynamic model. The model is driven by meteorological forcing fields including surface wind forcing, heat fluxes, solar radiation along with freshwater and nutrient (nitrogen and phosphorus) discharges of nine main rivers flowing to the wetland. The results are validated by comparisons of simulated outputs with field observations and remotely-sensed data. The model simulates the spatial and temporal distributions of water temperature, dissolved Oxygen (DO), Chlorophyll-a, and nutrients such as Ammonia-Nitrogen (NH3), Nitrate Nitrogen (NO3), and Orthophosphorus (OPO4). This study highlights that the water quality in this lagoon is impacted by physical, chemical, and biological processes. In addition, it is shown that there is a high correlation between the simulated and measured water temperatures. In addition, distrubution maps of water quality variables show a decrease in dissolved oxygen and an increase in chlorophyll-a in the western part of the lagoon. This model can be used to simulate, analyze and predict the long-term water quality status of Anzali lagoon
  9. Keywords:
  10. Water Quality ; Dissolved Oxygen ; Numerical Modeling ; Chlorophyll-A ; Anzali Lagoon

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