Modelling the nitrogen and phosphorus cycle in the Seydi suyu stream

ABSTRACT Master of Science Thesis MODELLING THE NITROGEN AND PHOSPHORUS CYCLE IN THE SEYDI SUYU STREAM SERDAR GÖNCÜ Anadolu University Graduate School of Natural and Applied Sciences Environmental Engineering Program Supervisor: Assoc. Prof. Dr. Erdem ALBEK 2001, 154 Pages In this study, the Şeydi Suyu stream draining the Şeydi Suyu watershed where intensive agriculture is practised has been modelled with respect to nitrogen and phosphorus. Nitrogen and phosphorus are added from diffuse sources in the watershed. The effects of diffuse sources have been determined by using export coefficients. Stream nitrogen and phosphorus cycles have been modelled by the QUAL2E model. The QUAL2E model has been coupled with the export coeffient approach to include the effects of diffuse sources to the stream. For a period of two years, monthly samples have been taken from two monitoring stations along the stream. Data from the first station have been used as model input and data from the second station has been used to calibrate the model. The observations and model results have been found to agree well. Moreover, sensivity analysis has been applied to model inputs and parameters. Keywords: QUAL2E, Diffuse Source Pollution, Nitrogen, Phosphorus, Modelling u