Treated surface water is used as water for human consumption, but the quality of the surface water before it enters the treatment plant is important because it may contain organic impurities, be turbid, or have too high temperature. All these are parameters that affect the quality of drinking water treatment, and their timely detection is even more important so that the treatment process can be adjusted. Until now, mainly conventional methods have been used to measure the parameters, which can take a lot of time. Recently, however, online measurement methods have emerged that are fast and take more frequent measurements independently of humans. In this paper, the results of the analysis of the raw water of Butoniga reservoir obtained by measuring with the online method using the probe Memosens Wawe CAS80E were compared with the results obtained by conventional methods in the laboratory. Temperature, turbidity, nitrates, and total organic carbon were compared. Online probe measurement proved to be an effective method for temperature, turbidity, and total organic carbon, and less effective for nitrates. Online measurement also proved to be a reliable method for measuring raw water quality, but the most efficient use of a probe is compared to conventional methods.