State Key Laboratory of Pollution Control and Resources Reuse, School of Environment, Nanjing University, Nanjing 210093, China.
Water Res. 2012 May 15;46(8):2591-604. doi: 10.1016/j.watres.2012.02.014. Epub 2012 Feb 20.
Thermal regime is strongly associated with hydrodynamics in water, and it plays an important role in the dynamics of water quality and ecosystem succession of stratified reservoirs. Changes in both climate and hydrological conditions can modify thermal regimes. Liuxihe Reservoir (23°45'50″N; 113°46'52″E) is a large, stratified and deep reservoir in Guangdong Province, located at the Tropic of Cancer of southern China. The reservoir is a warm monomictic water body with a long period of summer stratification and a short period of mixing in winter. The vertical distribution of suspended particulate material and nutrients are influenced strongly by the thermal structure and the associated flow fields. The hypolimnion becomes anoxic in the stratified period, increasing the release of nutrients from the bottom sediments. Fifty-one years of climate and reservoir operational observations are used here to show the marked changes in local climate and reservoir operational schemes. The data show increasing air temperature and more violent oscillations in inflow volumes in the last decade, while the inter-annual water level fluctuations tend to be more moderate. To quantify the effects of changes in climate and hydrological conditions on thermal structure, we used a numerical simulation model to create scenarios incorporating different air temperatures, inflow volumes, and water levels. The simulations indicate that water column stability, the duration of the mixing period, and surface and outflow temperatures are influenced by both natural factors and by anthropogenic factors such as climate change and reservoir operation schemes. Under continuous warming and more stable storage in recent years, the simulations indicate greater water column stability and increased duration of stratification, while irregular large discharge events may reduce stability and lead to early mixing in autumn. Our results strongly suggest that more attention should be focused on water quality in years of extreme climate variation and hydrological conditions, and selective withdrawal of deep water may provide an efficient means to reduce internal loading in warm years.
热状况与水的水动力密切相关，在分层水库的水质动态和生态系统演替中起着重要作用。气候和水文条件的变化都会改变热状况。流溪河水库（23°45'50″N；113°46'52″E）是位于中国南部北回归线的广东省的一个大型、分层和深水库。该水库是一个温暖的单温跃层水体，夏季分层时间长，冬季混合时间短。悬浮颗粒物和营养物质的垂直分布受热结构和相关流场的强烈影响。分层期底层缺氧，增加了底泥中营养物质的释放。本文利用 51 年的气候和水库运行观测资料，展示了当地气候和水库运行方案的显著变化。数据显示，过去十年空气温度升高，入流量波动加剧，而年际水位波动趋于缓和。为了量化气候和水文条件变化对热结构的影响，我们使用数值模拟模型创建了不同空气温度、入流量和水位的情景。模拟结果表明，水柱稳定性、混合期持续时间以及表面和流出温度都受到自然因素和人为因素（如气候变化和水库运行方案）的影响。在近年来持续变暖且储水更加稳定的情况下，模拟结果表明水柱稳定性增加，分层持续时间延长，而不规则的大流量事件可能会降低稳定性，并导致秋季提前混合。我们的研究结果强烈表明，在极端气候变化和水文条件下，应更加关注水质问题，选择性抽取深层水可能是减少温暖年份内部负荷的有效手段。
