Multi-objective optimization of cascade reservoirs using NSGA-II: A case study of the Three Gorges-Gezhouba cascade reservoirs in the middle Yangtze River,China

A multi-objective optimization model of cascade reservoirs was developed to maximize the power generation and minimizie the appropriate ecological flow shortage index (AEFSI) downstream from the reservoir. Additionally, the non-dominated sorting genetic algorithm (NSGA-II) was used to search for multi-objective Pareto optimal solutions. The paper took the Three Gorges-Gezhouba cascade reservoirs as a case study. After validating the model, data from three typical years were used in the optimization. The results indicated that maximizing power generation by adjusting the optimal rules increased power generation by 1.07%, 0.91%, and 1.03% in normal, wet, and dry hydrological years, respectively, while increasing the AEFSI by 22.12%, 11.78%, and 14.67% (compared to real operations). The AEFSI was improved (decreased) by 21.90%, 10.27%, and 18.52% when the optimal rules favored the downstream ecology, but power generation decreased by 1.61%, 1.06%, and 2.29%, respectively, in the different hydrological years. Moreover, the results provide a set of well-distributed optimal solutions along the Pareto front that allow decision-makers to easily determine the best compromised solutions based on the trade-offs between the economic and ecological benefits. The results of this study provide guidance for decision-makers to improve the comprehensive benefits of the Three Gorges-Gezhouba cascade reservoirs.     

A Hydro-Economic Model for Water Level Fluctuations: Combining Limnology with Economics for Sustainable Development of Hydropower

Water level fluctuations in lakes lead to shoreline displacement. The seasonality of flooding or beaching of the littoral area affects nutrient cycling, redox gradients in sediments, and life cycles of aquatic organisms. Despite the ecological importance of water level fluctuations, we still lack a method that assesses water levels in the context of hydropower operations. Water levels in reservoirs are influenced by the operator of a hydropower plant, who discharges water through the turbines or stores water in the reservoir, in a fashion that maximizes profit. This rationale governs the seasonal operation scheme and hence determines the water levels within the boundaries of the reservoir''s water balance. For progress towards a sustainable development of hydropower, the benefits of this form of electricity generation have to be weighed against the possible detrimental effects of the anthropogenic water level fluctuations. We developed a hydro-economic model that combines an economic optimization function with hydrological estimators of the water balance of a reservoir. Applying this model allowed us to accurately predict water level fluctuations in a reservoir. The hydro-economic model also allowed for scenario calculation of how water levels change with climate change scenarios and with a change in operating scheme of the reservoir (increase in turbine capacity). Further model development will enable the consideration of a variety of additional parameters, such as water withdrawal for irrigation, drinking water supply, or altered energy policies. This advances our ability to sustainably manage water resources that must meet both economic and environmental demands.     

A global optimization method for prediction of muscle forces of human musculoskeletal system

Inverse dynamic optimization is a popular method for predicting muscle and joint reaction forces within human musculoskeletal joints. However, the traditional formulation of the optimization method does not include the joint reaction moment in the moment equilibrium equation, potentially violating the equilibrium conditions of the joint. Consequently, the predicted muscle and joint reaction forces are coordinate system-dependent. This paper presents an improved optimization method for the prediction of muscle forces and joint reaction forces. In this method, the location of the rotation center of the joint is used as an optimization variable, and the moment equilibrium equation is formulated with respect to the joint rotation center to represent an accurate moment constraint condition. The predicted muscle and joint reaction forces are independent of the joint coordinate system. The new optimization method was used to predict muscle forces of an elbow joint. The results demonstrated that the joint rotation center location varied with applied loading conditions. The predicted muscle and joint reaction forces were different from those predicted by using the traditional optimization method. The results further demonstrated that the improved optimization method converged to a minimum for the objective function that is smaller than that reached by using the traditional optimization method. Therefore, the joint rotation center location should be involved as a variable in an inverse dynamic optimization method for predicting muscle and joint reaction forces within human musculoskeletal joints.     

Integration of research and management in optimizing multiple uses of reservoirs: the experience in South America and Brazilian case studies

The construction of large reservoirs in South America and particularly in Brazil has intensified within the last 50 years. Built up primarily for hydroelectricity production, these artificial ecosystems now serve purposes such as: water storage for public use; fisheries and aquaculture; recreation; tourism, and irrigation. These artificial ecosystems were also built up with the purpose of enhancing the regional development. These activities produce multiple impacts among which are eutrophication, a serious problems with various ecological, economic, and social consequences. Basic studies on reservoirs have identified their main ecological characteristics and described some of their fundamental mechanisms of functioning. This information cover: factors involved in reservoir complexity, such as spatial scale, vertical and horizontal heterogeneity, temporal variation at several time scales and, in some cases, watershed/reservoir relationships, and the impact of non-point and point sources of nutrients. Numerous studies have been dedicated to describing aquatic biota, its relationship with environmental factors, and the impacts of degradation/pollution/ eutrophication on biodiversity. Research priorities have been established mainly by limnologists in response to needs identified by environmental impact assessment. Due to the pressure of multiple uses, population growth, and economic factors, aquatic scientists now face a number of questions being posed by managers and engineers. These questions relate to a wide range of practical problems, the solutions to which depend on accumulated data related to the structural complexities and function mechanisms previously referred to. These problems can be divided into three main groups: (i) eutrophication processes and their characteristics, and water quality control; (ii) impact of fisheries, aquaculture, and exotic species introduction on the biota and the water quality; (iii) sustainable development of reservoirs and optimization management of their multiple uses. Predictive capabilities required in the face of these problems should be based on modeling development and intensive use of data-bases resulting from long-term studies on reservoirs. The predictions thus made possible would involve economic factors and the costs of recovery of eutrophic reservoirs. The experience of reservoir research and management in South America and in Brazil is, probably part of a world wide tendency on reservoir research and development with the aim to optimize multiple uses. Based on the cooperation of limnologists and engineers, ecosystem management models must eventually be applied at the watershed / reservoir level, where demands on the part of managers and decision makers will certainly promote a predictive, integrated, and adaptive approach,based on fundamental research.     

Optimized reservoir operation to balance human and environmental requirements: A case study for the Three Gorges and Gezhouba Dams,Yangtze River basin,China

After the construction and operation of the Three Gorges and Gezhouba dams, their impacts on hydrologic alterations in the middle and lower reach of Yangtze River are under high attention worldwide, of which the balance between the human and environmental flow requirements is one of the most important issues. This study uses an optimization model for the operation of reservoirs to compare the different environmental flow requirements of river ecosystems. Based on the different environmental flow requirements, four scenarios were established: (1) the no environmental flow case; (2) the minimum environmental flow (MEF) case; (3) the appropriate environmental flow (AEF) case; and (4) the environmental design flow (EDF) case. The EDF case is first proposed in this paper, which considers the reservoir adjustment ability and comprehensively balances the economic, social and ecological benefits. The Range of Variability Approach (RVA) is used to evaluate the potential hydrological alterations of each of the four scenarios. The comparison results of the power production and the degree of hydrological alteration in the four different scenarios, indicate that the system operation under the EDF case imposes the least hydrological alteration while providing adequate power production. The encouraging results demonstrate that this method will be a robust tool for practitioners to better perform reservoir operations in balancing the human and environmental requirements.     

辽河流域丰枯遭遇下水库调度

利用Copula函数分析辽河流域水库入库流量边缘分布及其生态径流量,得出水库可调水范围,在满足生态流量基础上,保障辽河流域城市供水。研究表明:(1)英那河与张家堡水库入库流量以对数正态分布为最佳边缘分布,其余水库入库流量最佳边缘分布均为广义极值分布,同时,Gumbel Copula与Frank Copula函数对水库入库流量拟合效果最优;(2)7组水库组合中有3组水库组合入库流量(白石与锦凌、白石与青山、张家堡与碧流河)丰枯异步概率高于丰枯同步概率,且枯枯遭遇概率较低,分别为13%,12%以及13%。其余4组水库组合枯枯遭遇概率皆高于27%,水库间入库水文过程发生同枯概率可能性较大;(3)使用90%保证率逐月频率计算法所求流量是辽河流域9个水库的最佳生态径流量。(4)枯水月水库间易发生枯枯遭遇,当水库间入库径流皆低于最小生态径流标准,水库无法对各自调水城市进行供水调度,其中,大伙房与桓仁、白石与锦凌、白石与青山主要在1、2月无法对沈阳、凌海和绥中县进行输水,桓仁与清河水库仅在2002年5月无法对开原进行供水,此时需考虑水库提前蓄水以满足城市用水需求。碧流河、英那河和张家堡水库虽两两存在无法输水情况,但可三者联动对大连进行联合调度,缓解无法输水问题。     

基于生态能量视角的我国小水电可持续性分析

我国的小水电开发经历了以解决农村地区用电短缺到当前以促进节能减排、清洁能源建设为目的的转变。运用生态能量分析的方法之一——能值分析方法,选取贵州省安龙县红岩二级水电站为案例,对其建设与运行的可持续性进行了系统分析,并与国内外大水电的相关指标进行了平行对比。结果表明:该水电站2010年电力产出的能值转换率为1.03×105sej/J,其可再生性比例为52.01%,在能值产出率、环境负载率和可持续能力等方面的表现均好于大水电。但其能值交换率为0.58,表明2010年水电上网价格偏低。小水电的不稳定运行也使其系统能值指标呈现波动变化,当实际发电量为设计发电量的50%时,水电的能值转换率接近于湄公河上大坝生产水电的能值转换率,可持续性指标的值从6.12急剧降到3.01。系统评估水电资源,作好流域小水电总体开发规划,保证小水电系统稳定运行是提高其可持续性的关键之一。     

A Hybrid Optimization Method for Solving Bayesian Inverse Problems under Uncertainty

In this paper, we investigate the application of a new method, the Finite Difference and Stochastic Gradient (Hybrid method), for history matching in reservoir models. History matching is one of the processes of solving an inverse problem by calibrating reservoir models to dynamic behaviour of the reservoir in which an objective function is formulated based on a Bayesian approach for optimization. The goal of history matching is to identify the minimum value of an objective function that expresses the misfit between the predicted and measured data of a reservoir. To address the optimization problem, we present a novel application using a combination of the stochastic gradient and finite difference methods for solving inverse problems. The optimization is constrained by a linear equation that contains the reservoir parameters. We reformulate the reservoir model’s parameters and dynamic data by operating the objective function, the approximate gradient of which can guarantee convergence. At each iteration step, we obtain the relatively ‘important’ elements of the gradient, which are subsequently substituted by the values from the Finite Difference method through comparing the magnitude of the components of the stochastic gradient, which forms a new gradient, and we subsequently iterate with the new gradient. Through the application of the Hybrid method, we efficiently and accurately optimize the objective function. We present a number numerical simulations in this paper that show that the method is accurate and computationally efficient.     

Difluoromethane, a New and Improved Inhibitor of Methanotrophy

Difluoromethane (HFC-32; DFM) is compared to acetylene and methyl fluoride as an inhibitor of methanotrophy in cultures and soils. DFM was found to be a reversible inhibitor of CH₄ oxidation by Methylococcus capsulatus (Bath). Consumption of CH₄ in soil was blocked by additions of low levels of DFM (0.03 kPa), and this inhibition was reversed by DFM removal. Although a small quantity of DFM was consumed during these incubations, its remaining concentration was sufficiently elevated to sustain inhibition. Methanogenesis in anaerobic soil slurries, including acetoclastic methanogenesis, was unaffected by levels of DFM which inhibit methanotrophy. Low levels of DFM (0.03 kPa) also inhibited nitrification and N₂O production by soils. DFM is proposed as an improved inhibitor of CH₄ oxidation over acetylene and/or methyl fluoride on the basis of its reversibility, its efficacy at low concentrations, its lack of inhibition of methanogenesis, and its low cost.     

近30年来三峡库区土地利用与生态环境效应研究热点演变及展望——基于Citespace的文献可视化分析

三峡库区作为三峡工程建设后形成的独特地理单元,梳理探讨其土地利用与生态环境效应已有研究成果,对于库区土地利用、生态可持续发展具有重要意义。基于Citespace软件及传统文献归纳方法对文献总体特征、热点演变、主要内容、存在问题与不足等分析发现:(1)土地利用与生态环境效应相关的中英文发文量持续增长,领域影响力增强,研究具有多学科、交叉性等特点;(2)研究经历了1990-2005、2006-2014、2015-2022年三个时段的演变:一阶段重点关注土地整理、土地生态保护等问题;二阶段重点关注消落带、土地利用变化的地形梯度效应等问题;三阶段重点关注景观格局变化的社会-经济生态耦合、生态系统服务等问题,与库区发展及区域政策相吻合;(3)库首、库腹、库尾关注的主要内容有所差异:库首研究以生态风险评价及生态系统服务为主;库腹侧重对坡耕地变化的社会生态经济耦合研究;库尾因建设用地较多,在土地整治及区域规划背景下进行研究;(4)土地利用变化从注重单一要素转向多要素、多功能研究,驱动因子研究从定性分析转向定性与定量相结合分析;退耕还林等生态政策实施以来区域生态系统服务总体呈上升趋势、生态风险指数明显下降;土地利用的生态环境效应研究内容更加多元化;(5)当下的研究面临着数据、方法、指标体系构建等问题,未来需要从理论构建、方法创新、实践应用等多方面进行探索。     

山美水库氮营养盐滞留特征及其影响因素的多时间尺度分析

水库对氮营养盐的滞留效应对水体富营养化防控有重要影响,为揭示不同时间尺度下水库氮营养盐的滞留特征及影响因素的差异,通过构建山美水库流域生态动力学模型,在统计水库氮滞留量和滞留率的基础上,从年、月、日不同时间尺度对氮营养盐的滞留效应进行分析;并通过多元线性相关分析,对入库流量、出入库流量比、水力滞留时间、流速、温度5种因素的影响进行研究.结果表明: 不同时间尺度下山美水库的氮滞留过程均呈现波动特征.在年尺度上,水库主要呈现正滞留效应,是流域重要的氮汇;在月尺度上,氮滞留呈现丰枯期变化特征,水库在源和汇的角色上发生转变;在日尺度上,枯水年氮滞留过程波动剧烈,滞留率在-300%～100%之间变化.不同时间尺度下,出入库流量比、流速因子均是影响水库氮滞留的重要因素;随着时间尺度的降低,入库流量和温度因子对氮滞留的影响程度有所增强;水力滞留时间对氮滞留的影响程度则随时间尺度变化而有正负差异.     

Effects of the allelopathically active macrophyte Myriophyllum spicatum on a natural phytoplankton community: a mesocosm study

The objective of this study was to identify potential effects of habitat conditions on parasite infection risk in reservoirs. For this, we compared parasite infection in 0+ perch (Perca fluviatilis L.) between reservoir sections: (1) along the longitudinal profile of Brno reservoir (inflow—main body—outflow), and (2) the transversal profile of Hamry reservoir (littoral and pelagic zones). Perch were predominantly infected with trophically transmitted endoparasites. Longitudinal parasite infection differed between sampling sections, showing different trends in particular parasite species between sections. The abundance of dominant Bunodera luciopercae was highest in the main body and lowest in the outflow, abundance of Proteocephalus sp. and Camallanus spp. decreased between the inflow and outflow, and abundance of Acanthocephalus lucii and ectoparasites (Gyrodactylus sp. and Argulus foliaceus) increased from the inflow to the outflow. Parasite diversity was higher in the outflow compared to other sections. No difference was observed in parasite abundance between littoral and pelagic perch subpopulations, though higher endoparasite diversity was found in the littoral zone. The results indicate that habitat type can influence parasite infection in perch through local food (intermediate host) availability. Fish–host behaviour is also discussed as a factor possibly influencing infection in perch.     

三峡库区典型流域聚落变迁的土地利用效应

三峡库区是典型的移民区和生态敏感区,探究其由于聚落变迁所引发的土地利用转移效应对于区域社会经济发展和生态恢复具有重要意义。以库区腹地草堂溪流域为研究对象,基于2000—2018年GOOGLE EARTH高分影像,结合当地自然地理环境和社会经济发展从微观尺度对山区聚落变迁的土地利用效应进行剖析。研究表明:(1)扩张型聚落周边以耕地转为果园为主;衰退型聚落周边土地利用转型主要表现为耕地向果园、有林地转变;自然增长型聚落周边以耕地和灌木林地向有林地,果园转化;消没型聚落周边以耕地,果园转为林草地,撂荒地为主,经济和生态效益均有所提高;且除消没型聚落外,另外3种聚落类型周边土地利用功能逐渐向生产生态功能转变,消没型周边土地利用功能逐渐侧重于生态功能。(2)2000—2010年,聚落变迁劳动力转移是聚落周边用地类型变化的根本因素,政府政策是是造成土地利用转型的直接因素;2010—2018年社会经济发展是土地利用转型的直接驱动因素,而农户生计需求是引发用地类型变化的根本驱动力;(3)聚落的变迁,不仅驱动了土地利用转型而且促使流域内经营主体由农户个体经营向政府、企业为主的经营主体转变。研究结果对于库...     

基于GIS的三峡库区云阳县生态经济区划

采用自上而下的生态要素宏观分析与自下而上的经济要素微观分析相结合的方法,运用GIS分析手段对复杂的自然生态要素与人类经济活动的时空变化及其相互作用进行分析和表达,以地处三峡库区腹地的典型山地县云阳为例,根据不同区域所表现出来的对生态变化与人类经济社会活动变化的承载力差异,即不同生态经济地域系统的稳定性、干扰能力、承受能力、生产能力和可利用方式的明显差异,进行综合生态经济区划。分区结果的命名体现了生态系统的地域特征和该区域生态经济发展的方向。通过对各生态经济区特征的分析。旨在协调日益激化的人地矛盾,探讨生态经济的发展方向、途径和对策,为三峡库区大尺度生态-经济-社会的可持续发展研究提供经验和样本。     

The use of direct-fed microbials for mitigation of ruminant methane emissions: a review

Concerns about the environmental effect and the economic burden of methane (CH₄) emissions from ruminants are driving the search for ways to mitigate rumen methanogenesis. The use of direct-fed microbials (DFM) is one possible option to decrease CH₄ emission from ruminants. Direct-fed microbials are already used in ruminants mainly to increase productivity and to improve health, and are readily accepted by producers and consumers alike. However, studies on the use of DFM as rumen CH₄ mitigants are scarce. A few studies using Saccharomyces cerevisiae have shown a CH₄-decreasing effect but, to date, there has not been a systematic exploration of DFM as modulators of rumen methanogenesis. In this review, we explored biochemical pathways competing with methanogenesis that, potentially, could be modulated by the use of DFM. Pathways involving the redirection of H₂ away from methanogenesis and pathways producing less H₂ during feed fermentation are the preferred options. Propionate formation is an example of the latter option that in addition to decrease CH₄ formation increases the retention of energy from the diet. Homoacetogenesis is a pathway using H₂ to produce acetate, however up to now no acetogen has been shown to efficiently compete with methanogens in the rumen. Nitrate and sulphate reduction are pathways competing with methanogenesis, but the availability of these substances in the rumen is limited. Although there were studies using nitrate and sulphate as chemical additives, use of DFM for improving these processes and decrease the accumulation of toxic metabolites needs to be explored more. There are some other pathways such as methanotrophy and capnophily or modes of action such as inhibition of methanogens that theoretically could be provided by DFM and affect methanogenesis. We conclude that DFM is a promising alternative for rumen methane mitigation that should be further explored for their practical usage.     

顾及城郊农田生态服务价值的中心城区生态安全网络重构

针对中心城区日益凸显的农业、生态、城镇三类空间冲突问题,借鉴田园城市理论,创新性地提出一种利用城郊高生态价值农田细化城市生态安全网络,构建"三生"空间协调有序的国土空间格局的方法。利用防城港市遥感影像、国土调查和社会经济数据,在城郊耕地综合评价的基础上,采用评价结果修正的当量因子法评估其农田生态价值。进一步利用InVEST、MSPA及MCR模型初步构建市域生态安全网络,再将高生态价值农田作为临时生态节点完成网络重构,并进行对比分析。以重构的新网络指导中心城区的规划分区优化,并对市域和中心城区两级生态网络要素的空间管控规则及联合管理机制进行了探索。结果表明:(1)防城港市区单位面积农田生态价值为35540元/hm²,高生态价值农田较均匀的环城分部。(2)重构后的网络新增34个临时节点和51条绿带,延长48.425 km,增加808.89 hm²生态源。(3)新网络能有效引导中心城区形成圈层发展结构,较原网络在连通性、有效性、稳定性上均有所提升。研究结果为注重协调发展的国土空间规划背景下区域空间格局优化提供了新的思路。     

基于系统动力学的重庆三峡库区生态安全情景模拟及指标阈值确定

根据重庆三峡库区生态系统的特征,建立了经济子系统、人口子系统和环境子系统的系统动力学模型,并在此基础上确定了其模型的主要参数和反馈关系,通过历史值与仿真值的对比进行了检验。选择了可持续发展型、资源衰竭型和自然状态型3种情景进行模拟最终确定其生态安全的指标阈值,并将其确定的阈值应用于生态安全评价指标,得出重庆三峡库区生态安全指标的综合得分,由此看出库区生态安全呈逐年递增的趋势,但仍然处于较为敏感的时期,需要相关部门的配合,从而最终实现库区的可持续发展。     

基于结构调整视角的吉林省产业生态化发展

基于产业系统与生态环境的交互胁迫作用关系,采用系统分析方法与综合指数评价法,对吉林省产业结构生态化水平进行综合评价,并刻画其时空格局特征.结果表明: 2000—2013年,吉林省产业结构生态化水平呈逐年递增态势,结构发育程度与资源环境效率均有显著提升;产业结构生态化发展地区差异呈现资源环境效率＞产业结构优化度＞产业结构生态化的关系特征,空间上呈现西高东低的格局特征,同时市域尺度上呈现以长春为核心向外围逐渐降低的“级差化”分异特征;依据产业结构优化度与资源环境效率的协调发展特征,可将全省划分为高水平协调、低水平协调、经济先行型、生态先行型4种生态化类型区.     

辽宁省清原县森林资源结构及其空间优化配置

利用RS、GIS技术和多目标灰色局势决策方法,综合森林的经济效益指标(生物量、林分生产力)和生态效益指标(涵养水源量、固土量),对清原县现有森林类型进行空间优化配置.结果表明: 经优化配置后,清原县森林类型的结构比例发生了明显的变化,其中针叶林和阔叶林面积由43%、51%减少到23%、31%,针阔混交林面积由3%增加到43%,灌木林面积保持不变;森林生态系统生物量、林分生产力分别增加0.6%、2.1%,而涵养水源功能增加31.7%,固土功能基本保持不变,在保留较高木材生产效益的同时,可充分发挥涵养水源功能,实现森林生态系统经济效益和生态效益的最大化.     

1996—2005年北京城市生态质量动态

从生态要素、生态过程、生态功能和生态问题4个主题出发,构建了包含16个指标的北京城市生态质量评价指标体系,并分别采用熵权法、最差状态法和最佳状态法对指标进行赋权,通过加权平均法构建了北京城市生态要素指数（EEI）、生态过程指数（EPI）、生态功能指数（EFI）、生态问题指数（EDI）和综合生态质量指数（CEI）,用以评价1996—2005年北京城市生态质量动态变化.结果表明：研究期间,北京城市EEI无明显改善,持续维持在远离理想点的水平;EPI和EFI改善显著,由1996年的远离理想点到2005年接近于理想点的水平;EDI的年度波动较大,普遍远离理想点;CEI得到持续改善,但离理想点依然有一定距离.当人均国内生产总值（GDP）小于3 000美元时,EPI、EFI和CEI随GDP的增长而快速增大,改善显著,当人均GDP超过3 000美元后,EPI、EFI和CEI随GDP增长而增大的速度减慢;EEI和EDI受人均GDP的影响较小,主要受限于自然条件及全球和区域环境的变化.