Date

2015

Author

Kuzyaka, Esra

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The earliest studies in Lake Eymir showed that the lake used to be in a clear water state with submerged and emergent plants; however 25 years of raw sewage effluent led to eutrophication of the lake. Therefore, restoration measures were carried out including diversion of the sewage effluent and biomanipulation and Lake Eymir is the first wellknown successfully biomanipulated freshwater lake of Turkey. Although raw sewage effluent was diverted and the external nutrient loading was reduced, Lake Eymir still suffers from internal phosphorus loading coming from the sediment. Additionally, climate change projections are expected to complicate the water quality of the lake in the future as higher temperatures can lead to lower water levels, higher nutrient concentrations and more cyanobacteria blooms. In this study, the aim was to understand the possible responses of Lake Eymir to nutrient loading increase and decrease scenarios, and water temperature increase scenarios using the PCLake lake ecosystem model. The model was calibrated (2001-2005) and validated (2006-2010) for five variables (i.e. chlorophyll a, PO4 and total phosphorus, NO3–N, NH4–N and zooplankton biomass). Most of the variables were adequately calibrated and validated (i.e. PO4 and total phosphorus, chlorophyll a and zooplankton biomass), while the other variables (i.e. NH4–N and NO3–N) were underestimated. According to the tested scenario runs both nutrient and climate scenarios showed significant differences compared to baseline simulation for all of the variables. Nutrient scenario results showed that Chl a, P and N increased and decreased when nutrient loading was increased and reduced respectively and were in agreement with the other studies. The water temperature scenario results, on the other hand, showed increases in Chl a with increasing temperature, but decreases in P and N concentrations which differed from predictions in the other model studies. Reasons for that might be the lake’s relative deepness and stratification; and uncertainty issues of the model. With the model it was observed that increasing nutrient load and water temperature lead to eutrophication of the lake.

Subject Keywords

Eutrophication., Lake restoration., Lakes, Climatic changes., Water levels.

URI

http://etd.lib.metu.edu.tr/upload/12619464/index.pdf
https://hdl.handle.net/11511/25127

Collections

Graduate School of Natural and Applied Sciences, Thesis