Generation-associated high-frequency oscillations in reservoir water levels and implications for inflow data quality: A case study of Chuncheon Dam, Korea

Study region This study focuses on Chuncheon Dam in the Bukhangang River basin, South Korea, a cascade reservoir system where precise real-time inflow estimation is critical for integrated water resources management and flood control. Study focus This study quantifies how millimetre-scale, generation-associated water-level oscillations propagate into 1-min inflow estimates. A targeted band-stop correction, applied to every month of 2023 whose stage record can resolve the oscillation, reduces the standard deviation of 1-min inflow by 21.7% over the record (40.8% in June 2023) while conserving cumulative inflow volume to within 0.02%. The negative-inflow count, widely used as a quality indicator, is also shown to be strongly affected by the 0.7 mm quantisation step of the stage sensor rather than directly reflecting estimation quality. New hydrological insights for the region Oscillation amplitude is not primarily controlled by absolute water level or mean power output; it correlates strongly with power-output variability and ramp rate, while elevated RMS amplitudes recur within specific operating water-level ranges. These results identify generation-associated oscillations as a manageable source of non-physical variability in short-interval inflow estimates. An operation-aware diagnostic procedure can reduce this variability when the monitoring record resolves the oscillation and satisfies both relative and absolute detection criteria. The procedure is transferable, whereas the target frequency band and amplitude threshold require site-specific identification.