This document contains dissolved oxygen (DO) concentrations and stable oxygen isotope data from the water column of a temperate drinking water basin in the Harz Mountains (Rappbode Basin, Germany; 51 44' 19 N, 10 53' 30 E). The study site was analysed over a 18-month period between June 2019 and December 2020 through depth profiles with a fortnightly sampling resolution. The document contains a description of oxygen dynamics in the epilimnion, metalimnion and hypolimnion of the lake. Data on depths affected by the occurrence of the metalimnetic oxygen minimum (MOM) are also reported. A quantification of metabolic processes such as respiration and photosynthesis through R/P ratios (Quay et al., 1995) is provided. In addition, the dependence of the ecosystem on atmospheric oxygen throughout the year in the context of climate change is highlighted. This is a supplementary material to Dordoni et al., 2022.