Prediction of oxygen regime indicators in Danube river

Purpose. To identify the dynamics of the oxygen regime of the Danube River and to develop a model for forecasting the oxygen regime of the Danube based on the analysis of biochemical oxygen demand (BOD) and reaeration processes, taking into account the multifactorial influence of ecological, hydrological, and anthropogenic factors. Methods. Statistical, the Streeter-Phelps mathematical model was applied. Results. The study used long-term data from the state monitoring of water resources of the Danube River on indicators of dissolved oxygen (DO) and biochemical oxygen demand (BOD5). The research showed an overall improvement in the oxygen regime of the Danube River during the period 2004–2023. All observation points demonstrated a stable increase in DO levels, especially after 2020, which may indicate a reduction in organic pollution. Seasonal analysis revealed that DO levels increase in the cold period and decrease in the warm period due to heightened biological activity. The Streeter-Phelps model confirmed its ability to predict the dynamics of DO and BOD5 with acceptable accuracy, although discrepancies were observed in some years due to short-term fluctuations in organic loading. Conclusions. The results of the study confirmed the effectiveness of using the Streeter-Phelps model to forecast the oxygen indicators of the Danube River. The forecast data can be used to assess the ecological state of the river, plan measures to improve water quality, and manage water resources. The developed recommendations will help minimize the risks of oxygen deficiency and support the preservation of ecological balance in the Danube River basin.