Primary data are 25 yrs of discharge (i.e. river flow) for multiple sites on the Ohio River. Supporting data are water quality variables for select sites on the Ohio river, including nutrient species, information from algal cell counts, and in-situ sensor data. This dataset is associated with the following publication: Nietch, C., L. Gains-Germain, J. Lazorchak, S. Keely, G. Youngstrom, E.M. Urichich, B. Astifan, A. DaSilva, and H. Mayfield. Development of a Risk Characterization Tool for Harmful Cyanobacteria Blooms on the Ohio River. WATER. MDPI AG, Basel, SWITZERLAND, 14(4): 644, (2022).