The purpose of this diploma thesis is to present the methods for measuring turbidity in watercourses and review the literature that estimates the amounts of suspended material. The first part of the thesis begins with a theory on the origin of suspended material. In addition, methods for measuring suspended material in watercourses and basic equations for determining suspended solids are presented. The second part analyzes the discharge and suspended material data from the Dvor gauging station on the Gradaščica river. This data can help us measure the content of suspended material in the watercourse, either in kilograms or tonnes. We can then use the calculated values to draw graphs which show the correlation between the volume of the discharge and the content of suspended material. Finally, uncertainty and equipment error are calculated.