A computer program, SPECIATION, was developed to deter-mine the detailed composition of an aqueous solution and the concentrations and activities of all species. Once the detailed composition of an aqueous solution is known, it is possible to determine the saturation level of the solution with respect to any mineral, which is silica for this study. Three water samples from the Kizildere geothermal field of Turkey were collected and the chemical analyses of these samples were used as input data in SPECIATION to determine their detailed composition for obtaining the silica scaling potential of the Kizildere field effluent. The analysis of the silica scaling studies indicate that the pH of the power plant effluent of the Kizildere field increases due to boiling and loss of acid gases (mainly CO2). This increase in pH results with an increase in the solubility of amorphous silica. As a consequence, the silica scaling danger of effluent is carried to lower temperatures, which makes the problem-fee temperature range wider.