Surface water includes rivers, lakes, streams, and other watercourses that are exposed to various pollution sources such as wastewater, agricultural activities, and atmospheric precipitation. Water quality has a significant impact on human health, living conditions, and overall life quality and it also promotes the socioeconomic development of communities. Water quality is assessed using physical-chemical, biological, and microbiological indicators in order to ensure its safety for human consumption,, industrial needs, and agriculture. Surface water sampling which was used for the purpose of this master thesis was conducted from April 2023 to March 2024 at five locations in Varazdin County (Lonja, Presecno, Ljubelj, Ljuba voda, and Koruscak), and the following indicators were measured: total organic carbon (TOC), potassium permanganate consumption (KMnO¤), and biochemical oxygen demand after 5 days (BOD5). The results of the analyses from five locations in Varazdin County showed seasonal variability in water quality indicators. The highest values of TOC were recorded at the Ljuba voda and Koruscak locations, particularly in the summer months, while BOD¥ was significantly higher at the Koruscak and Ljubelj locations, indicating the presence of organic matter. KMnO¤ consumption also varied, with elevated values during warmer periods, suggesting increased organic pollution during these times.