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Simulation of Phosphorus in Urban Lakes and the Impact of Structural and Management Measures on Phosphorus Loading (Case Study: Chitgar Artificial Lake)

Mahmoudi Anzabi, Amir | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46870 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Agha Mohammad Hossein Tajrishi, Massoud
  7. Abstract:
  8. Chitgar Lake, lake located in the north-west of Tehran City, Iran, is an artificial and recreational lake. The total area and volume of this lake are about 132 hectares and 6.9 million cubic meters, respectively. According to the increased temperature, the lake ecosystem is faced with problems such as augmentation of vermin, frogs and algae in the lake area. Qualitative measurements of 59 well taken samples from March 2013 to June 2014, demonstrate that ratio of total nitrogen to total phosphorus is in the range of 21 to 82 with an average of 42. Consequently, phosphorus is the restricting factor for eutrophication in this lake. In this study, by scrutinizing various scenarios, factors effecting eutrophication conditions are considered. AQUATOX software which is developed by Environmental Protection Agency (EPA) is used for simulating phosphorus in this lake. Validation of the model based on the data recorded in the first year of operation of the lake depicts that performance of the proposed model in simulation of total phosphorus and total nitrogen are identical. The Nash-Sutcliffe efficiency coefficient value for total concentration of phosphorus for the whole period is -3.72. Having used the summer and first half of the fall data, the coefficient increased to -0.29. Due to water intake during February, average maximum concentration of phosphorus in the lake increases by 31%. So, water intake should be avoided in this month. If water available from Kan River is not sufficient to enter the lake, Replacement percent of evaporated water can be reduced, because reduction in incoming water (up to 20% of volume of required water) has little impact (about 6%) on the average phosphorus concentration during the five-year period of operation of the lake. Simulation during a period of five years shows that complete removal of phosphorus from water entering the lake can attenuate the maximum concentration of phosphorus in the fifth year up to 37%. Using bypass scenario is not suitable for scenarios involving water entering in February. But In other water entering patterns, quality of the lake is improved. Release and growth of fishes, cannot solely have a long-term effect on the amount of phosphorus in the lake (up to 13.2%). Development an appropriate and sustainable ecosystem for fishes compatible with the lake will take time and this process takes at least three years. Thus, if fish population surpasses capacity of the lake or if fishes are not compatible with lake characteristics, then fishes will be subjected to severe mortality
  9. Keywords:
  10. Eutrophication ; Kan Basin Reservoir ; Phosphorus Modeling ; Chitgar Artificial Lake

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