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Modeling the water quality in Ulubat Lake

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2007
Yenilmez, Firdes
Lakes can be used for recreational purposes, agricultural irrigation, domestic water supply or industrial use. However, these functions of the lakes can be impaired due to excess nutrient loadings from industrial facilities, agricultural activities, and discharge of wastewaters from sewage systems. Uluabat Lake is one of the important lakes in Turkey faced with water quality problems due to excess nutrient loading from point and non-point sources. In this study, Water Quality Analysis Simulation Program (WASP Version 7.2), supported by the Environmental Protection Agency (EPA), was used to simulate the water quality of the lake. The model was calibrated using a set of data belonging to the time period from January 1st to June 1st, 2000, for dissolved oxygen (DO), chlorophyll-a (Chl-a), ortho-phosphate (PO4-P) and nitrate (NO3-N). An acceptable similarity was obtained between the predicted and observed water quality values in calibration. Then, the model was verified for another data set. Verification period was from 1st of June to 31st of December, 1999. Verification results were also coherent with the observed values. Following the calibration and verification, the model was used as a management tool to predict the future quality conditions for the lake for different management scenarios. According to the results, sediment dredging had a significant impact on the water quality. Additional methods on top of sediment dredging improved the quality of the lake. The best result was obtained when buffer zone was formed, phosphorus loads from the Mustafakemalpaşa District sewage system and Emet and Orhaneli Watersheds were decreased by 50% and 50% decrease was considered in the fertilizer usage throughout the agricultural lands, in addition to sediment dredging.