College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, Jiangsu, China.
School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
J Environ Manage. 2019 Oct 15;248:109250. doi: 10.1016/j.jenvman.2019.07.021. Epub 2019 Jul 26.
A temperature-control curtain (TCC) is a new technique of selective withdrawal for controlling the outflow temperature of a reservoir. A TCC can significantly affect the reservoir hydrodynamic and thermal structure, but its effects on water quality and ecology remain unknown. In this study, we developed and calibrated a hydro-thermal-water quality model to numerically analyze how a TCC located 1 km from a dam affected algal biomass and water quality in a reservoir. According to our results, when a TCC was used, the mean annual chlorophyll a (Chl-a) concentrations in the reservoir decreased. Chl-a concentrations remained constant during the heating period until normal water levels were reached, and increased during the cooling period and decreased until year-end drawdown levels were reached. The dissolved oxygen (DO) concentrations decreased and the anoxic proportions increased throughout the year. The yearly mean Chl-a and DO concentrations in the reservoir declined continuously as the water-retaining proportion (P) of the TCC increased from 0 to 87.5%, while the anoxic proportion (DO < 2 mg/L) first increased and then decreased, peaking at a P of 62.5%. The change patterns of the anoxic proportion were consistent with those of thermal stability, demonstrating the applicability of thermal stability in predicting reservoir hypoxia. Moreover, the environmental impact of TCCs will increase under global warming, and TCCs can mitigate the increased algal biomass and further decrease DO in warmer climate conditions. Under a medium-high climate scenario, Representative Concentration Pathway 6.0, and a TCC having 75% P, the yearly mean Chl-a, DO concentrations, and anoxic proportions of Sanbanxi Reservoir are predicted to reach 10.7 μg/L, 4.2 mg/L, and 39.6%, respectively, by 2046-2065. Thus, changes in the water environment and ecology (particularly the likely deterioration of water quality because of selective withdrawal under global warming) should be considered as a component of water management practices.
一种温度控制幕帘（TCC）是一种新的选择性放水技术，用于控制水库的出流温度。TCC 会显著影响水库的水动力和热结构，但它对水质和生态的影响尚不清楚。在本研究中，我们开发并校准了一个水热水质模型，以数值分析位于大坝 1 公里处的 TCC 如何影响水库中的藻类生物量和水质。根据我们的结果，使用 TCC 时，水库的平均年度叶绿素 a（Chl-a）浓度会降低。Chl-a 浓度在加热期保持不变，直到达到正常水位，然后在冷却期增加，直到达到年底放水水位。溶解氧（DO）浓度全年下降，缺氧比例增加。随着 TCC 的保水比例（P）从 0 增加到 87.5%，水库的年度平均 Chl-a 和 DO 浓度连续下降，而缺氧比例（DO<2mg/L）先增加后减少，在 P 为 62.5%时达到峰值。缺氧比例的变化模式与热稳定性一致，表明热稳定性可用于预测水库缺氧。此外，在全球变暖下，TCC 的环境影响将会增加，并且 TCC 可以在更温暖的气候条件下减轻藻类生物量的增加，并进一步降低 DO。在中高气候情景下，代表浓度途径 6.0 下，一个具有 75%P 的 TCC，到 2046-2065 年，三板溪水库的年度平均 Chl-a、DO 浓度和缺氧比例预计分别达到 10.7μg/L、4.2mg/L 和 39.6%。因此，水环境和生态的变化（特别是在全球变暖下选择性放水可能导致水质恶化）应被视为水管理实践的一个组成部分。
