河道型水库库湾水体富营养化评价及防治初探

目前我国河道型水库库湾水体污染问题普遍存在.葛洲坝水库是典型的河道型水库,水库蓄水以后,在黄柏河下游形成具有湖库特征的库湾,库湾水体发生富营养化.库湾水动力条件改变加上上游输入充足的营养物质,使库湾水体发生富营养化.利用黄柏河1998～2002年库湾断面监测资料,评价黄柏河水体富营养化现状,分析其富营养化成因,并据此提出可行的防治措施.     

香溪河库湾春季营养盐空间差异性成因分析

三峡蓄水后,香溪河库湾春季水体中营养盐分布呈明显的空间差异性,具体表现为总氮含量大致呈从上游到河口逐步升高的趋势,而总磷含量呈从上游到河口逐步降低趋势.为明确库湾水动力条件对库湾营养盐空间分布的影响,本文采用三维数学模型模拟了三峡蓄水后香溪河水动力场的分布,利用示踪方法分析了三峡蓄水初期香溪河库湾水动力场对春季营养盐时空分布的影响.结果表明,春季库湾近河口区域水体表现出明显的分层分向流动特征,长江干流水体与库湾水体间的交换作用显著,相应磷营养盐也随水流带出库湾,干流水体对香溪河库湾磷营养盐有明显的稀释作用,特殊的水动力条件是库湾营养盐空间分布差异性主要成因.研究可为三峡水库正常调度运行后香溪河库湾富营养化的控制和治理提供方法,也可为相似库湾营养盐的分布特征研究提供参考.     

三峡库区支流库湾水体富营养化演变特征研究

支流库湾水体富营养化是三峡水库蓄水带来的主要水环境影响特征之一。根据对不同历史蓄水期间三峡库区各支流库湾的水质变化特征及富营养化状态分析表明:三峡水库从试验性蓄水阶段进入常态调度运行后,支流库湾的水动力条件被进一步削弱,入河污染物扩散能力大幅度降低,库湾水质逐渐变差,各支流库湾普遍表现为中、富营养级水平,年内整体表现为春季高于秋季。从三峡库区支流库湾水体富营养化演变特征来看,库湾水动力条件由河流态改变为湖库态是其发生水体富营养化的主驱动力因素,陆域营养盐输入是库湾水体富营养化演变的物质基础     

三峡库区香溪河回水区营养状态变化特征与驱动因子

基于2015—2016年香溪河回水区域主要水质参数和营养状态的周年监测数据,分析并探讨三峡库区香溪河库湾回水区营养状态的季节性变化特征及潜在污染来源。结果表明:(1)香溪河回水区TN、TP污染十分严重,在调查时段内,各月份香溪河库湾水体的TN、TP质量浓度均远高于限制值,易发生水体富营养化;(2)香溪河回水区水体营养程度较高,所有月份均达到中营养以上水平,并在2015年8月达到富营养状态。水体营养状态从低到高季节顺序为秋季、冬季、春季、夏季。TN质量浓度是影响香溪河回水区水体富营养化程度最重要的指标;(3)香溪河回水区TN主要来自农业面源污染和城镇生活污水排入,流域上游的磷矿资源开采产生的工业废水以及库湾沿岸的点源污染是水体中CODMn与TP污染负荷的主要来源。水体中Chl-a质量浓度受TN、TP等营养盐的限制较弱,SD受浮游藻类和悬浮物的共同影响。     

三峡水库支流库湾营养源解析及水体富营养化调控对策研究

支流库湾水体富营养化是三峡水库带来的主要环境问题之一,三峡水库进入常态调度运行后,支流库湾水体富营养化问题日益突出.为厘清易发生水华的支流库湾水体富营养化的驱动力因素,本文以重庆市奉节县梅溪河为典型支流,采用三维水动力与水环境模拟技术解析了支流库湾水动力的驱动机制及营养盐来源及其组成.干-支流水温差导致的密度流是梅溪河...     

基于模糊数学的大伙房水库营养状态评价

分别采用营养状态指数法和模糊综合评价法对2015年大伙房水库进行富营养化评价,对评价结果进行对比分析显示:大伙房水库水体整体处于中营养~轻度富营养型状态,但总氮指标已达到中度富营养化程度,水库上游区域的富营养化程度高于库中心区,在严重的干旱年,容易出现富营养化状态加重和暴发水华的风险。模糊综合评价法既考虑了富营养化级别划分的模糊性,又考虑了不同评价因子对富营养化程度的影响权重,评价结果更加客观合理。     

基于flushing time的春季水库优化调度可行性研究

针对三峡水库支流库湾春季水华问题,通过建立三维水动力模型,探讨了利用调峰调度和潮汐式调度促进干支流水体交换的可行性。研究表明,当4月水库实施调峰调度时,整个库湾水体的flushing time较常规调度有所缩短,尤其是库湾上游至中上游区域;当5月水库开始实施潮汐式调度时,水体体积较大的库湾下游区域的flushing time较常规调度方案有所缩短。可见,两种水库优化调度方案对增大干支流水体交换均具有可行性。当水库实施调峰调度和潮汐式调度联合调度时,整个库湾水体的平均flushing time较常规调度方案有不同程度的缩短,表明该联合调度方案更能促进干支流水体的交换。研究成果可为支流库湾水环境问题的防治提供借鉴。     

三峡库区大宁河库湾水体混合过程中的营养盐行为

为研究不同水文期不同水体混合模式下大宁河库湾的营养盐行为,基于2012年大宁河的现场监测数据,分析营养盐时空分布特征,采用箱式模型对不同水文期营养盐的收支量进行计算,以期为制定大宁河富营养化和水华控制策略提供理论依据。试验及计算结果表明:在泄水期,干流水体通过表层逆向进入库湾,而支流水体通过底层潜流向河口运输;在汛限期和蓄水期,干流水体主要通过中上层逆向进入库湾,而支流水体通过底层潜流向河口运输。干流对支流的逆向顶托作用常年存在,泄水期、汛限期、蓄水期干流对支流的贡献率分别为70.38％、28.42％和59.56％。在水体混合过程中,库湾上游来水以及干流顶托来水的混合作用是控制库湾水化学组成的主要物理因素。     

丹江口水库典型库湾及支流富营养化评价研究

为客观评价丹江口水库的水质,在库区选择了习家店和神定河2个实验区,对水体进行采样分析。分析结果表明：总体看来,丹江口水库水体富营养化状况较轻,绝大部分为中营养化状况;典型支流和库湾在特定的时段内为富营养化状况,习家店富营养化状况居中,神定河富营养化状况较严重;从年内时间分布来看,夏季水体富营养化状况均较秋季严重;从年际时间分布来看,2011年水体富营养化状况轻于2010年同期水平。     

河道型水库富营养化及水华调控方法和关键技术

本文提出了河道型水库富营养化及水华调控的系统研究方法,重点探讨了水利水电工程影响下的河道型水库富营养化及水华监测、模拟及调控方法及关键技术,包括流域水环境监测评估与水华预警系列技术,大型水库多维、多场耦合富营养化模拟系统,以及改善河道型水库支流库湾水温层化进而抑制水华暴发的调控方法等,以期为抑制河道型水库支流库湾水华暴发、改善水库水质提供参考和依据。     

三峡库区支流中水体的垂向掺混对于藻类生长的影响

三峡水库蓄水之后库区支流水华问题给当地生态环境造成了较大影响,也引起了广泛的关注和重视,然而针对这一问题尚未取得很好的解释和解决方案。本文采用EFDC模型对于2008年坝前库区干支流的三维水动力和水质进行了数值模拟,并从水体垂向掺混的角度分析支流的水华现象。模拟结果成功再现了香溪河库湾中的温度分层和异重流现象,流场、温度场的计算值和实测值吻合较好。统计结果表明:长江干支流水动力特性的差异显著,干支流垂向紊动黏性系数、垂向紊动扩散系数沿垂线分布呈现出不同的形态,且长江干流的垂向掺混强度明显高于香溪河。同时,叶绿素浓度与垂向紊动扩散系数呈显著的负相关关系,随着水体垂向紊动扩散系数的增加,叶绿素浓度逐渐降低,这一规律的发现可为采用物理方法防治三峡库区支流水华打下基础。     

三峡水库香溪河库湾水华水动力调控初步研究

针对三峡水库蓄水运行后支流库湾春季水华频现问题,利用CE-QUAL-W2模型建立了香溪河-三峡库区整体立面二维水动力数学模型,对三峡水电站不同开机数量和春季不同水文条件下的香溪河库湾流速进行了数值模拟。计算结果表明:香溪河上游来流量较小时,滞留区表层流速小于香溪河库湾水华的临界流速0.05 m/s;而香溪河上游来流量增大到合适的值时,香溪河滞留区表层流速可大于0.05 m/s;仅利用三峡电站小幅度日调节对支流库湾流速的改善效果十分有限,而利用干支流水库对香溪河库湾流速的联合调控效果明显,可控制三峡水库香溪河库湾水华爆发。     

Driving factors of the flushing time of bays formed where tributaries enter a reservoir

Flushing time is an integrative parameter that can represent water exchange capacity and sensitivity to pollution threats. As bays formed where tributaries enter the Three Gorges Reservoir of China have experienced frequent algal blooms over the past decade, we examine the spatially variable flushing time of a typical tributary bay (Xiangxi Bay) by numerical tracer experiments. First, the tracer concentration reduction could be approximated well by a double exponential decay curve, and the local flushing time of Xiangxi Bay is determined using key flushing coefficients. Second, a sensitivity analysis is performed to examine the influence of upstream inflow, temperature difference, wind, water level of the reservoir, and daily water level fluctuation on the spatial variation in local flushing time. Finally, according to local flushing time values and the sensitivity analysis results, the bay can be generally characterized by three zones: riverine, transitional, and mainstream‐influenced zones. In particular, the local flushing times in the riverine zone are mainly affected by the upstream inflow. The difference in temperature between the reservoir mainstream and Xiangxi Bay is the main forcing in the transitional and mainstream‐influenced zones. This study is the first to investigate different driving factors for flushing time in a typical reservoir tributary bay. The findings provide insights on the transport processes in such water bodies, suggesting the possibility of using the longitudinal zonation of flushing time for reservoir management.     

An ensemble of Bayesian SPARROW models for the Precambrian Shield in the eastern Georgian Bay drainage basin,Ontario, Canada

The present study applied an ensemble of Bayesian SPARROW models in the eastern Georgian Bay drainage basin informed by multi-agency tributary water quality monitoring data collected in the area. Consistent with our current understanding of the role of wetlands in the Precambrian Shield, our analysis showed that they could be responsible for nearly 30% of the total phosphorus (TP) loading from forested areas and 23% of the delivered TP from the eastern Georgian Bay drainage basin. Agricultural areas contribute over 40% of the TP loading associated with anthropogenic activities, which was two times higher than the predicted nutrient losses per unit area in southern Georgian Bay. This finding raises concerns regarding the likelihood of elevated eutrophication risks from future expansion of agriculture in central and northern Ontario. Considering the uncertainty pertaining to their broader influence, cottage septic fields were estimated to be the second anthropogenic P source after agriculture, accounting for 9% of the delivered TP loading to the downstream outlets into Georgian Bay. Research on eutrophication of coastal embayments in Georgian Bay has historically focused on factors, such as basin morphometry, internal P loading, and dreissenid-mediated nearshore shunt. In this context, our SPARROW model offered an additional perspective by estimating that a significant fraction (≈90%) of the TP loading delivered to the Georgian Bay embayments could be originating from upstream sites, even though our predictions suggested that nearly half (49%) of P loading reaching the stream network deposits on the sediments of inland lakes in central Ontario.     

三峡电站日调度驱动的支流振荡对支流水温垂向结构的影响

三峡电站日调度驱动的重力波对其支流动力过程造成显著影响,其中的高频水流波动会显著影响支流库湾的物质、能量等垂向扩散和输运过程,进而影响水华暴发等环境问题。基于三峡水库香溪河支流2021年蓄水期末的水动力及水温垂向结构监测数据,分析了三峡电站日调度驱动的支流库湾高频振荡对水温结构的影响。研究发现,三峡出库流量日波动驱动支流水位也呈日波动和高频波动特征,其中水位日波动振幅约0.3~0.5 m,高频水位波幅约0.04 m。库湾底层水温高频波动比中上层更加明显,与香溪河库湾水深从河口向上游逐渐变浅有关系。支流近底水温波动功率谱分析显示,香溪河湍流耗散速率(6.5×10^-7 W/kg)明显高出一般水库的近底耗散率,表明水库调度驱动的水体高频波动导致较强的湍流发育和耗散。     

Factors influencing thermal structure in a tributary bay of Three Gorges Reservoir

To better understand the factors influencing the thermal structure of tributaries in the Three Gorges Reservoir(TGR),a well validated three-dimensional hydrodynamic and water temperature model was proposed to simulate the water temperature distribution in the Xiangxi Bay, a representative tributary of TGR.The numerical results show that water temperature stratification seasonally occurred in the Xiangxi Bay, with stable vertical temperature profiles.It is found from the numerical experiments that three key factors are responsible for the formation of water temperature structure:(1) very often,the locations of thermocline are mainly determined by wind speeds, and the higher the wind speed is, the deeper the thermocline is located beneath the water surface,which could be expressed by a fitted exponential function,(2) the thermal structure is affected by static stability of water column, and the thermocline becomes closer to the water surface and its thickness increases with the increase of temperature, (3) due to the effect of the thermal density inflow, the water temperature of the hypolimnion tends to be uniform, however, even under the condition of larger inflow discharge,the influence of the inflow on the epilimnion and the thermocline is not significant.     

三峡水库香溪河库湾水环境容量研究

三峡水库蓄水后,水库回水区的水文情势发生了显著变化,香溪河库湾受回水顶托,营养物质大量富集,致使该库湾的许多污染指标超标,直接威胁流域生态、经济的可持续发展.欲有效地改善香溪河库湾水环境质量,必须研究库湾的水环境容量,并以此作为污染防治的依据,对主要污染物实行总量控制.通过对香溪河库湾水质野外监测和数据分析,表明主要污染物为PO4、NH4.应用WASP水质模型,对三峡水库香溪河库湾进行水质模拟.根据水质模拟结果,采用解析法、功能区段首控制法定量计算出了香溪河库湾各功能控制区段的水环境容量,各控制区污染物应削减量或可新增加量,并初步地提出了一些相应的污染治理措施.     

Eutrophication model for river-type reservoir tributaries and its applications

With the impoundment of the Three Gorges Reservoir, algal blooms have been found in some tributaries. In this study, according to the theoretical analysis of the eutrophication mechanismin a river-type reservoir tributary, a one-dimensional eutrophication model was developed for the Xiangxi River tributary of the Three Gorges Reservoir, and the influence of hydrodynamic conditions on the primary growth rate of algae was investigated. Furthermore, numericalpredictions of hydraulic variables and eutrophication factors, such as the concentration distribution of TP, TN, and Chl-a in the spatial and temporal domains, were carded out. Comparison of computation results of TP, TN, and Chl-a concentrations along the river in the spring of 2005 with experimental data demonstrates the validity of the model. The agreement between the computation results and the experimental data of TP and TN concentrations is better than the agreement between those of Chl-a concentration. The simulated results also show that the Chl-a concentration downstream is much higher than that in the upstream tributary, which potentially indicates the outbreak of algae in this area. Therefore, this study provides a feasible method of accurately predicting the state of eutrophication in river-type reservoirs and their tributaries.     

三峡水库香溪河库湾不同异重流下水温分层模式研究

三峡水库蓄水后支流库湾水体的水动力条件发生变化,水温在垂向上的分布也呈现出了不同模式。为了分析不同类型的倒灌异重流条件下水体的水温分布情况,对香溪河库湾不同断面的水温进行原位监测,并构建库湾水体的水温水动力数学模型(CE-QUAL-W2)。研究结果表明:水库正常运行的不同时期,香溪河库湾水体的主要水动力条件和水温分布结构均不同,在水库运行时的泄水期,库湾水体水动力主要为表层倒灌异重流,水温呈现传统的分布模式;在水库汛期低水位运行时,库湾水体水动力主要为中层倒灌异重流,水温呈“双混斜”式分布;在水库蓄水期,库湾水体水动力主要为底部倒灌异重流,水温呈“半U”型分布。研究成果可为揭示香溪河水流水温特性、营养盐迁移及水华预测预报提供相关的理论支持和技术支撑。