During flood periods, rivers transport large amounts of water and nutrient loads, and have significant impacts on water quality and ecosystems in enclosed waters. In this study, observations were carried out in the Yodo River, the three upstream rivers (the R. Katsura, the R. Uji, and the R. Kizu), and the Yamato River in ordinary and flood conditions. As a result, the relationships of SS with PN, PP, and POC were formulated, and we could estimate the loading amounts of PN, PP, and POC, using these correlations and the turbidity measured by automatic monitoring system. In a similar way, from the monitoring electric conductivity data, the loading amounts of DIN and PO4-P were estimated with a high degree of accuracy in the Katsura River, where the water quality was influenced strongly by point source pollution.