Helmholtz Centre for Environmental Research, Department of Lake Research, Magdeburg 39114, Germany; College of Water Conservancy, Shenyang Agricultural University, Shenyang 110866, China.
Helmholtz Centre for Environmental Research, Department of Lake Research, Magdeburg 39114, Germany.
J Environ Sci (China). 2024 Dec;146:127-139. doi: 10.1016/j.jes.2023.06.025. Epub 2023 Jun 26.
Water-level reduction frequently occurs in deep reservoirs, but its effect on dissolved oxygen concentration is not well understood. In this study we used a well-established water quality model to illustrate effects of water level dynamics on oxygen concentration in Rappbode Reservoir, Germany. We then systematically elucidated the potential of selective withdrawal to control hypoxia under changing water levels. Our results documented a gradual decrease of hypolimnetic oxygen concentration under decreasing water level, and hypoxia occurred when the initial level was lower than 410 m a.s.l (71 m relative to the reservoir bottom). We also suggested that changes of hypoxic region, under increasing hypolimnetic withdrawal discharge, followed a unimodal trajectory with the maximum hypoxic area projected under the discharge between 3 m/sec and 4 m/sec. Besides, our results illustrated the extent of hypoxia was most effectively inhibited if the withdrawal strategy was applied at the end of stratification with the outlet elevation at the deepest part of the reservoir. Moreover, hypoxia can be totally avoided under a hybrid elevation withdrawal strategy using surface withdrawal during early and mid stratification, and deep withdrawal at the end of stratification. We further confirmed the decisive role of thermal structure in the formation of hypoxia under water-level reduction and withdrawal strategies. We believe the conclusions from this study can be applied to many deep waters in the temperate zone, and the results should guide stakeholders to mitigate negative impacts of hypoxia on aquatic ecosystems.
水库水位经常下降，但人们对其对溶解氧浓度的影响了解甚少。本研究使用了一个成熟的水质模型，以说明德国 Rappbode 水库水位动态对氧浓度的影响。然后，我们系统地阐明了在水位变化下，选择性取水对控制缺氧的潜力。研究结果表明，在水位下降过程中，湖底层的溶解氧浓度逐渐降低，当初始水位低于 410 米时（相对于水库底部的 71 米），会出现缺氧现象。我们还表明，随着下泄流量的增加，缺氧区的变化遵循单峰轨迹，最大缺氧区出现在 3 米/秒至 4 米/秒之间的下泄流量下。此外，如果在分层结束时应用取水策略，将出水口设置在水库最深处，可以最有效地抑制缺氧程度。此外，采用表层取水和分层结束时的深层取水相结合的混合取水策略，可以完全避免缺氧现象。我们进一步证实了在水位下降和取水策略下，热结构在缺氧形成中的决定性作用。我们相信本研究的结论可应用于温带地区的许多深水区域，研究结果应为利益相关者减轻缺氧对水生生态系统的负面影响提供指导。
