In this study, correlations between seasons and parameters in the Geum River, South Korea, were examined using the hourly measurement data of water quality parameters by a real-time, automatic water-quality monitoring station. Correlations between measures of water quality provided by this station exhibited the same trends as those acquired by manual measurements; in both cases, water temperature showed high correlations with DO and pH. Inflow-pollution-source items (TOC, TP) showed positive correlations with, and were much influenced by, water temperature and precipitation. These two parameters had negative correlations with TN, which acts as a growth-limiting factor for algae. Linear regression analysis revealed that water temperature could be used to explain variations in DO (86.0%), pH (77.4%), TOC (51.7%), TN (39.6%), and TP (34.5%), at most. DO and TOC could explain variations in pH (90.8%) and TP (34.5%), respectively. The daily cycles of change in water temperature, DO, and pH showed trends similar to that of air temperature. Generally, they were highest from 13:00 to 16:00 hours, and lowest from 05:00 to 07:00 hours. The daily differences (largest in summer and smallest in winter) were most apparent in Bonghwangcheon, which is a tributary of the Geum River.