High-resolution real-time monitoring was employed and evaluated using three real-time monitoring techniques for anions at the river Rhine in Koblenz, Germany. These are a sensor for nitrate in situ and ex situ, a colorimetric device for nitrate and nitrite, and an online ion chromatography (IC) for fluoride, bromide, chloride, nitrate, nitrite, phosphate, and sulfate. The original data are presented on Zenodo. Data presentation and evaluation are presented in the paper "Online high-resolution real-time monitoring techniques for anions in river water". The paper is published in the journal Environmental Monitoring and Assessment.