Hypoxia in stratified waters greatly threatens aquatic ecology and societal development owing to enhanced nutrient discharge and increasing global temperature. Current research predominantly alleviates hypoxia by reducing dissolved oxygen (DO) consumption or conducting hypolimnetic oxygenation, yet their implementation has encountered bottlenecks. Therefore, this study explores the potential of increasing the inherent DO supplies in stratified reservoirs to mitigate hypoxia. High-frequency observations and massive modeling experiments are integrated to discern the DO supply mode and the dominant driver of DO evolution. Results indicate that periodic thermodynamic conditions determine the DO supply relationships between oxygen sources (inflow carriage, reaeration, and photosynthesis) for different water layers. Thermal stratification causes the hypolimnion to rely mostly on the inflow for DO supply, leading to a fragile budget prone to hypoxia. However, episodic hydrodynamic events (turnover, wind stir, density current, and flood) can promote DO supply and inhibit hypoxia. Temperature and DO regimes are primarily driven by outflow conditions, followed by inflow and meteorology conditions. Furthermore, hypolimnetic hypoxia can be regulated by altering inflow volume, outflow volume, and outlet elevation. These findings highlight the importance of longitudinal solute exchange in DO evolution in stratified reservoirs, providing a basis for alleviating hypoxia through cascade reservoir operations.

中文翻译：

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分层水库中的氧气演化及其驱动因素：从供应方角度了解缺氧缓解策略


由于营养物质排放增加和全球气温升高，分层水域缺氧严重威胁水生生态和社会发展。目前的研究主要通过减少溶解氧（DO）消耗或进行低阈值氧合来缓解缺氧，但其实施遇到了瓶颈。因此，本研究探讨了增加分层水库固有溶解氧供应以缓解缺氧的潜力。高频观测和大规模建模实验相结合，可以识别溶解氧供应模式和溶解氧演化的主要驱动力。结果表明，周期性热力学条件决定了不同水层氧源（流入输送、再曝气和光合作用）之间的 DO 供应关系。热分层导致低水位主要依靠流入的溶解氧供应，导致预算脆弱，容易缺氧。然而，偶发的水动力事件（翻转、风搅动、密度流和洪水）可以促进溶解氧供应并抑制缺氧。温度和溶解氧状况主要由流出条件驱动，其次是流入和气象条件。此外，可以通过改变流入量、流出量和出口高度来调节低浅层缺氧。这些发现强调了纵向溶质交换在分层水库溶解氧演化中的重要性，为通过梯级水库运行缓解缺氧提供了基础。