The Çaygören Reservoir was sampled monthly from February 2007 to January 2009 at three stations to determine the relationships between the chlorophyll-a (Chl-a) dynamics and soluble reactive phosphorus (SRP), nitrate-nitrogen (NO3-N), ammonium-nitrogen (NH4-N), water discharge, water transparency, water temperature (T), specific conductance (SC) and pH. Thermal stratification occurred in the reservoir from May to September. The maximum chlorophyll-a concentrations were measured (using a YSI multi probe) in the fall and the minimum concentrations were recorded in the winter. Differences in the concentrations of chl-a, SRP and NO3-N were significant among seasons (pP<0.01), but not among sampling stations (p>0.01). The differences in the Secchi disk transparency were significant both among sampling stations and seasons (pP<0.05). The results of this study suggest that high chl-a concentrations resulted from the increase in available light in the spring and deep mixing in the fall which provided nutrients needed for phytoplankton growth