基于数据同化的深水湖库水温中短期预报

深水湖库的水温分布与演化影响着水体运动、生化反应和水生生物的新陈代谢过程,在中短期时间尺度上预报水温变化对湖库水质管理与生态环境安全十分必要。本文基于集合卡尔曼滤波算法与CE-QUAL-W2模型,构建可综合考虑模型参数、边界条件以及观测数据不确定性的湖库水温数据同化系统,利用水库调度数据与气象数据作为预报条件,将该系统应用于大黑汀水库进行1～10 d的中短期水温预报。结果表明：当集合数为100、模拟误差和观测误差分别为10%和1%时,同化系统能够兼顾较高的计算效率与模拟精度。同时校正模型参数和状态变量,能够使数据同化系统在不同水深处的水温模拟精度较无数据同化模拟结果提升41.2%～68.8%。随着预报期由1 d延长至10 d,各水深的预报误差由0.22～0.35℃增大至0.77～1.09℃。无论水库处于分层期或混合期,数据同化系统均能够在预报期内的气象条件及水库调度等内外部因素驱动下维持较高的准确性,高精度的水温中短期预报方法可以为湖库供水与生态安全提供理论与技术支撑。     

大型水库热分层的水质响应特征与成因分析

为研究大型水库热分层期间水质的响应特征及成因,于2018年4月-2018年12月对大黑汀水库坝前水体的水温及溶解氧等理化指标进行了连续性垂向监测,在此基础上分析了大黑汀水库季节性热分层变化规律以及各水质指标的响应特征.结果表明:(1)大黑汀水库水体呈典型的单循环混合模式,热分层期间,溶解氧在垂向分布同样表现出季节性变化...     

分层型水库水温水质耦合模型研究及其应用

水库水温分层不仅对水库水质的降解过程产生影响,更重要的是通过对水库流场的作用进一步影响库区水质分布,并对下泄水质产生影响,因此对分层型水库的水质模拟必须考虑水温分层影响.建立了宽度平均的立面二维水温水质耦合模型,采用建立的数学模型对某拟建水库水温水质进行了模拟.结果表明,分层型水库库区水质受温度场、流场影响明显,存在垂向分层、纵向差异等现象.研究成果可为水库水环境影响评价及保护提供参考.     

水库水温结构及其对库区水质影响研究

大型水库的建设在发挥巨大作用的同时,也带来了一些环境问题,引起人们广泛的关注,水温分层问题便是其中之一。针对水库水温分层问题,介绍了水库不同水温结构的类型及特点,总结了水库水温预测的最常用的方法:包括经验法和数学模型法,并分析了两种方法的适用条件及计算精度;探讨了水库蓄水后库区水动力特性的改变以及分层结构对库区水质的影响。研究结果表明:水库蓄水后,库区纵向流速分布自库尾至坝前段逐渐减小,水温分层会导致其它水质参数如溶解氧(DO)、pH值、化学需氧量(COD)等的分层,为水库的水温计算和库区生态环境影响评价提供依据。     

基于水下自走式监测系统的数据分析与应用

应用德国弗劳恩霍夫系统应用中心研制的多功能水下自走式监测与分析系统,以湖州市对河口水库、日照市青峰岭水库、南京市金牛山水库、秦淮河为试点,对上述水库及河流的多参数水质(溶解氧、电导率、铵盐含量、硝酸盐含量、温度)进行监测。基于所测数据,采用水下三维地形图、水质参数等值线图、分层切片图、纵向剖面图、水质参数散点图等方法,对上述水质参数在水体中的分布规律进行分析,对水下三维地形进行解释,对不同水质参数之间的相关关系进行一定探索。研究表明:在水库表面,溶解氧含量分布在空间上存在一定差异;硝酸盐含量分布在不同深度水体中差别很小,但在靠近底部时发生明显变化,与库底淤泥影响有关;随着水深的增加,水温逐渐降低;水面电导率值和硝酸盐、铵盐含量有一定的正相关关系,溶解氧和温度存在一定的负相关关系。应用结果表明:所测数据可快速生成水下地形及水质三维结构图,能较好地反应试点区域水情、水质的主体分布。     

水库缺氧区时空演化特征及驱动因素分析

湖库水体在热分层时期的缺氧现象将严重影响底层水体水质,破坏底层水生生物栖息环境,导致湖库整体水质及生态环境质量的下降。本文以引滦入津源头工程大黑汀水库为例,研究了水库热分层及缺氧区的时空演化特征,识别了在一定的水质及底质污染状况条件下,水库缺氧区形成与演化的主要驱动因素。研究表明,大黑汀水库缺氧现象出现时间为每年6月份至10月份,最严重时全库有60%的回水区域会出现缺氧问题,坝前延伸距离可达12.0 km。缺氧区内水体溶解氧浓度低于2.0 mg/L。研究认为,热分层状况是决定水体溶解氧状况及缺氧区演化的主要驱动因素;藻类浓度通过对溶解氧结构及底层水体耗氧条件的影响驱动了缺氧区的年内演化规律;水库的地形条件变化是水体缺氧区形成的重要辅助性因素;水动力学条件则主要影响水库缺氧区的稳定性。     

基于神经网络的水库藻类预警模型研究

针对水环境水体富营养化现象日渐严重导致控制水质难度和成本增高情况,对华南地区S水库进行藻类水质监测及风险预警研究。根据水库藻类水华产生的特点,通过对近一年水库气象、水质数据的整理与分析,建立基于神经网络的S水库藻类水华短期智能预警模型。预警模型选取水库水温、pH、叶绿素总浓度、总磷、总氮、溶解氧6种水质指标作为神经网络预警模型的输入量,分别采用BP神经网络、广义回归网络对S水库藻类建立预警模型并对两种预警模型的特点进行分析与总结,并通过对预测精度和泛化能力等因素的综合比较推荐最优预警模型结构和参数值。     

湖库水源选择性取水水质模型及应用

深水型水库作为城市重要供水水源,纵向上通常呈现明显的水质分层,不同水位出流水质不同。在优选纵向一维水质模型基础上,运用Matlab平台将模型程序化,开发了应用于选择性取水构筑物的出流水质预测软件;在西北某水库选择性取水塔的取水实例中,利用水库纵向水质数据,对温度、密度、溶解氧、电导率、氧化还原电位等13项出流水质指标进行了模拟验证,研究结果表明软件预测的出流水体的温度、溶解氧、电导率、pH、硬度、总氮指标与实测数据吻合,相对误差在10%以下,氨氮等指标预测误差较大。该软件可为深水型水源水库出流水质优化调度及水厂的运行控制提供参考。     

大黑汀水库水质时空变化特征及下游引水策略

为探究大黑汀水库2017年养鱼网箱拆除后水质特征,于2018年分季节采集水库表层和分层水样分析水库水质时空变化特征。结果表明:大黑汀水库表层水体总氮在冬季最高,总磷在夏季最高,硝态氮是溶解性无机氮中的主要成分;大黑汀水库总氮、硝态氮、总磷和磷酸盐质量浓度总体上都表现出上游最高、中游次之、下游最低的空间分布特征,氨氮和亚硝态氮则相反;垂向上主要表现为夏季总磷质量浓度底层大于表层,与温跃层及溶解氧水平有关;养鱼网箱拆除后显著降低了水库总磷和磷酸盐质量浓度,氨氮质量浓度也显著降低,总氮和硝态氮质量浓度无显著变化;氮磷比表明磷是该水库水体富营养化的限制因子,因此养鱼网箱拆除能有效控制该水库富营养化进程;根据水质时空分布特征,下游引水应避免在冬季取水,引水高度上应选择从坝前中层水柱取水。     

潘家口水库热分层期溶解氧垂向分布及影响因素

为探究水库热分层对溶解氧垂向分布的影响,2019年8月在潘家口水库设置监测平台,分别采用YSI-EXO2监测仪和NISKIN采样器进行监测和水样采集,测定库区水温、溶解氧、pH、浮游植物等水质指标的垂向分布,分析水体热分层期溶解氧垂向分布的影响因素及溶解氧极小值（MOM）的形成原因。结果表明：潘家口水库8月存在显著热分层现象,水温呈混合层-温跃层-滞温层结构。混合层溶解氧浓度大于6.5 mg/L;温跃层受热分层等影响显著,层内出现MOM,梯度明显增大,浓度显著减小;滞温层溶解氧逐渐恢复。相关性分析表明：溶解氧与水温和浮力频率显著相关,热分层是MOM形成的主要物理因素;溶解氧与浮游植物生物量和pH呈正相关,温跃层浮游植物的呼吸作用、营养物质的积累和有机物质的氧化分解等生物和化学因素在一定程度上促进了MOM的发展。     

Modelling approach for characterizing thermal stratification and assessing water quality for a large tropical reservoir

The dynamics of water temperature, dissolved oxygen and total dissolved solids concentrations in Aguamilpa Reservoir was analysed by considering horizontal and water column variations. The reservoir model, CE‐QUAL‐W2, was used to simulate the temporal variations calibrated with data gathered every 2 months from June 2008 to June 2009. Temperature depth profiles indicated a typical asymmetry of reservoirs exhibiting a large stratification in the lower part near the dam. Dissolved oxygen concentration profiles exhibited some degree of anoxia in the bottom water during the rainy season (May through October). This is most likely due to decomposition vegetation and organic matter via soil erosion and run‐off from the basin accumulating at the bottom of the reservoir. The reservoir stratification is clearly seasonal, occurring during the rainy season, especially in the lowest reservoir zones. The CE‐QUAL‐W2 model results provided a comprehensive understanding of the temporal behaviour of the study variables during the modelling study period. Application of this water quality model is directed to water resource managers to help them better understand the dynamics of physico‐chemical processes, and how they vary temporally and spatially in the reservoir, and to propose the best management practices for preserving or improving the water quality of the system.     

STUDY ON VERTICAL WATER TEMPERATURE MODEL FOR MIYUN RESERVOIR

1.　INTRODUCTIONLocated in the valleys ofnortheast Beijing,the Miyun reservoir is half-closed.Itsmax-im storage capacity is4 .375× 1 0 9m3.And itssurface area and maxim depth are1 88km2 and4 3.5m,respectively.Table1　Temperature stratification data of Miyun reservoirStation KD KX BBDepth(m) 0 .5 1 42 70 .5 1 9370 .5 1 7351 991 ,5 1 4.0 1 2 .0 8.0 1 4.0 1 0 .0 9.0 1 2 .4 1 2 .0 1 0 .01 991 ,6 2 1 .2 1 8.0 1 3.0 2 5.0 1 4.0 1 1 .0 2 5.0 1 3.0 1 0 .01 991 ,72 7.0 2 4 .0 1 9.0 2 7.0 1 5…     

Characterization of water quality in a small hydropower plant reservoir in southern Brazil

The construction of large reservoirs can cause profound environmental changes. Reduced water flow, increased water residence time, thermal stratification, increased sedimentation rates and decreased dissolved oxygen concentrations are examples of such changes. These changes can affect water quality and the biota in the environments adapted to the natural conditions of a river. Small reservoirs developed in conjunction with hydropower plants, however, could reduce the degraded water quality. This study focuses on characterizing water quality in a small hydroelectric reservoir. The study reservoir has an area of 1.4 km² and a short water retention time. The Monte Claro Hydroelectric Power Plant is part of a complex consisting of three plants on the Antas River in the north‐west of Rio Grande do Sul state, Brazil. The reservoirs associated with these plants are operated as run‐of‐the‐river facilities. Monitoring results obtained by CERAN, the Energetic Company of Antas River (Companhia Energética Rio das Antas), were used to evaluate the reservoir water quality. Three samples were collected seasonally (spring, summer, autumn and winter) in the area of influence of this plant following the filling of the reservoir (2005–2008). The examined water quality parameters were electrical conductivity, colour, turbidity, alkalinity, pH, biological oxygen demand (BOD), chemical oxygen demand (COD), total phosphorus, dissolved oxygen, sulphate, nitrate, nitrite, ammonia, suspended and dissolved solids, chlorophyll‐a, total and faecal coliforms, water temperature and Secchi depth transparency. The results were interpreted using an index of water quality, Trophic State Index, reservoir water quality and CONAMA Regulation 357/05 (Brazilian legislation). Based on these analyses, no significant changes were exhibited in the water quality of the reservoir from the hydroelectric plant operation.     

大型分层水库翻库特性及溶解氧响应研究

翻库对分层水库的水生态环境具有重要意义。通过在大型深水水库潘家口水库的原位监测结合垂向二维水动力-水质-水生态模型对翻库特性及溶解氧(DO)响应进行研究,分别对2018和2020年的水环境过程进行模拟。结果显示,水温分层导致了DO垂向分层,表层DO与气温相关性强,底层DO在分层后持续下降至0,秋季翻转是底层复氧的主要途径。2018年平均运行水位较2020年高14.2 m,表层温水层最大厚度2018年比2020年增加了近10 m,水库翻库从库尾逐渐向坝前推进。在库尾到坝前的距离约30 km的水域,2018年翻库的历经时间比2020年缩短40 d,坝前DO的垂向均匀时间滞后于水温7~10 d。水库水位较低时,翻库产生的表层水体DO下降幅度更大,降幅为3~4 mg/L。分别对水库不同断面可用势能指数(APE)对分层稳定性的过程进行分析,水库在不同年份和不同位置断面的翻库日期与夏季混合循环期的平均APE指数大小具有较好的相关关系。研究为探求大型深水分层水库水环境演变规律,科学合理进行调度提供理论基础。     

LM—BP神经网络在于桥水库水质预测中的应用

利用BP神经网络的改进算法（L-M）,通过对大量样本进行多次的训练学习,建立于桥水库水质预痢模型,用该模型对于桥水库高锰酸盐指数、五日生化需氧量、氨氮、溶解氧等污染指标进行了预测,预测结果表明,LM—BP神经网络模型用在于桥水库水质预测时是可行的,可以得到较为理想的的精度和可靠度。     

溪洛渡-向家坝-三峡梯级水库水温分布特性

梯级水库蓄水运行后,改变了河流的天然水流情势和水体的年内热量分配,水库内的水温分布特性随之变化。为了解溪洛渡-向家坝-三峡梯级水库蓄水运行后河道水温分布特征,对梯级水库沿程19个断面水温进行了观测,并根据观测资料系统地分析了梯级水库进出库水温和沿程水温分布,以及垂向温度分布变化情况。研究结果表明:溪洛渡、向家坝、三峡梯级水库的下泄水温在降温季节略有增加,在升温季节略有下降,形成了"高温不高,低温不低"的平坦化现象;溪洛渡和向家坝水库坝前区域在垂向上均出现明显的温度分层,而三峡水库近坝区的温度分层现象在梯级水库运行后明显减弱,近几年表层和底层水温相差最大值仅为2.5℃。研究结果可为梯级水库联合调度、水生态研究、水库水温数学模型验证等提供参考。     

Modeling the oxygen regime of stratified reservoirs

Conclusions A mathematical model is proposed for the oxygen regime of a stratified reservoir. A model is based on representation of the reservoir on the whole or its layers individually as an ideal mixer. The thermal regime of a stratified reservoir is schematized by a two-layer model-epilimnion and hypolimnion, which provide the plane with a pronounced variation in water temperature (thermocline). In calculating the oxygen regime, the epilimnion and hypolimnion are considered individual reservoirs with their own water balance, which is linked, however, to the water balance of the reservoir on the whole. Characteristic features of the aeration and reaeration of the epilimnion and hypolimnion, and also the selectivity of water intake from the reservoir are considered here. Practical use of the model is illustrated in an example of the calculation of the oxygen regime of a hypothetical stratified reservoir, the characteristics of which are determined on the basis of field data derived from observations on the water bodies of the Zagorsk water-storage power plant. The proposed model can be used to predict the oxygen regime of stratified reservoirs and the ecological feasibility of nature-conserving measures directed toward improving the quality of their water and conserving fauna. Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 10, pp. 27–32, October, 1998.