Risk- and robustness-based solutions to a multi-objective water distribution system rehabilitation problem under uncertainty .

The water distribution system (WDS) rehabilitation problem is defined here as a multi-objective optimisation problem under uncertainty. Two alternative problem formulations are considered. The first objective in both approaches is to minimise the total rehabilitation cost. The second objective is to either maximise the overall WDS robustness or to minimise the total WDS risk. The WDS robustness is defined as the probability of simultaneously satisfying minimum pressure head constraints at all nodes in the network. Total risk is defined as the sum of nodal risks, where nodal risk is defined as the product of the probability of pressure failure at that node and consequence of such failure. Decision variables are the alternative rehabilitation options for each pipe in the network. The only source of uncertainty is the future water consumption. Uncertain demands are modelled using any probability density functions (PDFs) assigned in the problem formulation phase. The corresponding PDFs of the analysed nodal heads are calculated using the Latin Hypercube sampling technique. The optimal rehabilitation problem is solved using the newly developed rNSGAII method which is a modification of the well-known NSGAII optimisation algorithm. In rNSGAII a small number of demand samples are used for each fitness evaluation leading to significant computational savings when compared to the full sampling approach. The two alternative approaches are tested, verified and their performance compared on the New York tunnels case study. The results obtained demonstrate that both new methodologies are capable of identifying the robust (near) Pareto optimal fronts while making significant computational savings.     

Responses of fishes and lampreys to the re‐creation of meanders in a small English chalk stream

River rehabilitation initiatives have become commonplace in European water courses as a result of European Union Water Framework Directive requirements. However, the short‐term responses of fishes to such work have thus far been varied, with some river rehabilitation efforts resulting in demonstrable improvements in diversity and size structure, whereas others have resulted in little or no change. Electrofishing and channel character surveys were conducted annually between 2009 and 2014 on a reach of the River Glaven (North Norfolk, UK) before and after rehabilitation work (embankment removal in 2009 and re‐meandering in 2010) as well as on a control reach immediately upstream. To assess the effects of rehabilitation work, before‐after‐control‐impact analysis tested for changes in channel character (geomorphology, substratum composition, and mesohabitat structure) and in fish species richness, relative abundance, population density, and size structure (calculated after fish data entry into the UK Environment Agency's National Fisheries Population Database). Following re‐meandering work (i.e., treatment), habitat heterogeneity and depth variation increased in the treatment reach, but fish responses were not significant except for biomass and density increases of brown trout Salmo trutta and abundance decreases of European eel Anguilla anguilla, in the treatment but not the control reach. These results are consistent with comparable river rehabilitation initiatives elsewhere, and they suggest that larger‐scale rehabilitations are probably needed to produce greater increases in fish density and diversity. It is recommended that future rehabilitation initiatives address catchment‐scale factors that can enhance ecosystem recovery, for example, removal of barriers to colonization, and increases in connectivity and water quality issues linked to eutrophication, elevated fine sediment inputs, and various pollutants.     

沿海港闸水下补强加固施工技术试验研究

本文针对水下混凝土病害整治的传统方法中围堰排水施工的缺陷，提出了病害混凝土水下补强加固新技术，即:水下封缝灌浆堵漏—水下老混凝土凿毛处理—水下植筋（含布设钢筋网片）—水下浇筑不分散混凝土，该项技术首次应用于苏北沿海黄沙港闸反拱底板裂缝修补加固工程。现场模拟施工试验表明:这一叠合防渗、整体补强技术切实可行，是传统围堰排水施工方法的重大突破；水下浇筑层不分散混凝土各项力学性能指标均满足工程加固设计要求，新老混凝土结合良好，有效地恢复了混凝土结构的整体性能；经济效益和社会效益显著，推广应用前景广阔。     

Estimating the Cost and Carbon Impact of a Long Term Water Main Rehabilitation Strategy

Research has shown that some water utilities still have a strong preference for using “tried and true” open cut replacement techniques when rehabilitating water pipes in urban areas. Significant cost savings and reductions in carbon emissions can, however, be realised through the implementation of a strategy that incorporates trenchless rehabilitation techniques. This paper investigates the carbon emissions and financial implications of pipe rehabilitation strategies and analyses policies for three water utilities in Australia over a long-term planning horizon (30 years). When monetized, the carbon emissions from pipe rehabilitation are shown to be 0.1–0.2 % of the total revenue of a utility. However, given that direct and intangible cost reductions can be realised and there is a need to mitigate carbon emissions wherever possible, it is concluded that utilities should develop the capacity to use trenchless techniques in urban areas.     

Water Resources Development Planning in a Basin Context in the Absence of Good Hydrologic Data: An Example from Sri Lanka

This paper describes a methodology for planning rehabilitation of small-scale irrigation systems in dry zones where the hydrologic database is poor. The methodology includes a two-stage decision-making process. The first stage relates to selection of cascades (meso-watersheds) within the basin for rehabilitation planning. The second stage is concerned with selection of tanks within a cascade and the type of rehabilitation components to be planned, taking into consideration the resource potential of the cascade and the socioeconomic factors of farmers. The methodology has been field-tested in Sri Lanka and shown to be efficient. A key principle underlying this approach is that development of any use of water within a basin must be viewed in the context of the whole basin to avoid conflicts over water use. Another principle is that hydrological and non-hydrological criteria must be used together to evaluate water resources development proposals.     

A Prioritization Model for Rehabilitation of Water Distribution Networks Using GIS

Decision-making for the rehabilitation of water distribution networks in the traditional procedure is based on some simple indices such as the number of incidents while several mechanical, hydraulic and qualitative factors are involved in this process. Evidently, making decision on the rehabilitation of water networks seems to be very difficult as the number of factors increases and they interact with each other. The main objective of this research is to prepare, implement and evaluate a conceptual model to prioritize the rehabilitation of pipes based on different scenarios with respect to the combination effects of basic factors in physical, hydraulic and experimental categories. In order to organize the wide range of data to be used in decision-making models, including the plans aimed for pipe replacement, it is necessary to use geographical information systems (GIS). By determining and introducing the factors involved in the rehabilitation of water networks, this research aims to provide an integrated model consisting of conceptual, GIS, hydraulic analysis and the breakage models to prioritize the rehabilitation schemes. By using the data provided from a real network, the advantages of the proposed methodology are evaluated. Based on the obtained results, age factor, among all the other physical parameters, and pressure, among the hydraulic factors, have the greatest influence in outlining the final rehabilitation scenario. The importance of the pipe length has decreased considerably as well. Furthermore, it can be concluded that rehabilitation management of pipe networks can be optimized by using this methodology.     

Comparison Among Resilience and Entropy Index in the Optimal Rehabilitation of Water Distribution Networks Under Limited-Budgets

The replacement of existing pipes is a strategy for the rehabilitation of water distribution networks that is frequently adopted by water companies. Usually, the optimal choice of the pipes diameter is a difficult optimization task, because limited budgets are available. In order to support the selection of a rehabilitation strategy, surrogate reliability measures are often used as an indirect measure of the water distribution system hydraulic performance. Among others, the resilience and entropy indices have attracted considerable interest because they both represent a measure of the network robustness. In the present work, a comparison between these indices is provided in the framework of the optimal rehabilitation of an existing network under limited budget constraint. The resilience and entropy indices are applied to the case of a realistic water distribution network in an extended period simulation framework. Several values of the maximum budget allocable for rehabilitation are considered, and hydraulic calculations are undertaken by means of a pressure driven approach within a modified EPANET 2 environment. The effectiveness of the two surrogate reliability measures is demonstrated by an a-posteriori reliability assessment.     

水生态恢复的经济学思考--对海河流域水生态恢复研究的几点建议

水生态恢复是恢复并维持退化水生态系统的服务功能的人类经济活动。导致水生态系统退化的原因多种多样,而人类经济活动的不当是主要的作用因子。在研究海河流域水生态恢复的过程中,有必要对传统不合理的水事经济制度诱发水生态系统退化的机理和过程开展系统研究、对水生态恢复目标预期可能实现的经济效益进行认真评价以及对推动水生态恢复的水权制度和排污权制度改革提出构想,同时探讨一下水生态恢复产业化的政策框架和机构设置。     

大型灌区节水改造技术支撑体系及研究重点

针对大型灌区节水改造工程建设与管理中存在的主要共性问题，综述国内外相关技术发展趋势与主要特征。总的趋势是目标趋于综合性、方法趋于多元性、手段趋于多样性；其特征为利用现代高科技、重视节水综合技术和精量灌溉节水技术以及环保技术。本文提出我国大型灌区节水改造技术支撑体系及当前应着手开展的与之相应的重点科学研究内容：包括评价方法、产品开发、地下水利用、农田排水再利用、泵站改造、环境效应等方面的课题。     

减水河段水力生态修复措施的改善效果分析

通过二维水力模拟计算,对深槽和挡水堰不同组合的修复方案,即在河道横断面上设置深槽以及纵向上间隔设置挡水堰等工程措施,对减水河段的水力生态修复措施进行研究。以四川某山区河流一段120m长的河段为例,根据代表鱼类对水深、流速适应度的曲线,计算出权重可使栖息地面积(WUA),并使用其来分析生境改善效果,同时还对影响河段沿程增温率的水力参数进行了对比分析。计算结果表明：在河道流量为1．65m\+3/s(约为多年平均流量的5％)时,采用深槽修复可增加WUA约48％,再在深槽基础上设一道拦水堰后共可增加WUA约84％;同时深槽还可使河流沿程增温率下降,使水温更接近减水前的状况。采用多道拦水堰将有助于尽可能多地提高栖息地面积,但拦水堰间距也不应过小,该河段拦水堰间距在30m左右为宜。分析表明,采用深槽加多道拦水堰的水力生态修复措施可以起到明显改善减水河段生境状况的作用。     

Rehabilitation scenarios for reservoirs: Predicting their effect on invertebrate communities through machine learning

Reservoirs are ecosystems that provide important services and reserves of aquatic biodiversity, especially in arid and semiarid regions. However, they are also highly vulnerable to pollution, water abstraction and land use change. Here, we aimed to develop a “dirty‐water” predictive model that could be used to create recovery scenarios and analyze the effect of measures on the biological quality of reservoirs. Accordingly, we constructed a machine learning predictive model that was trained with environmental and macroinvertebrate community data from 129 sites, sampled in six reservoirs in Northeast Brazil. Two different rehabilitation scenarios were simulated (D1 = lower improvement, 25% change; and D2 = higher improvement, 75% change), and three initial levels of disturbance were considered based on PCA analyses: least disturbed, moderately disturbed and severely disturbed. The effects were analyzed in terms of changes in expected taxa (E), observed/expected taxon ratio (OE), biotic and trophic status indices and the spatial distribution of sensitive taxa. The simulations resulted in significant improvements (p < .001) for all disturbance levels and indicators analyzed. Furthermore, rehabilitation measures in artificial systems, such as reservoirs, could result in a higher biodiversity, biological quality and water quality, also in the least disturbed sites. Thus, this approach has the potential to provide information on management and conservation measures, since the simultaneous predictions of many taxa can be used, including: mapping the distribution of species; monitor the population dynamics of species at risk of extinction; and determining the best rehabilitation measures to improve disturbed ecosystems, allowing the determination of the most cost‐effective restoration measures.     

A spatial assessment of riverine ecosystems and water supply in a semi‐arid environment

A spatial assessment was conducted in the semi‐arid area of South Africa, to: (1) identify priority areas for the conservation of river and groundwater ecosystems; (2) examine surface and groundwater quality for human consumption and (3) investigate the rehabilitation of degraded areas to highlight ‘win‐win’ situations for both environmental and human use. A systematic conservation plan was produced, highlighting river conservation areas (river types, fish species and connectivity areas), moderate‐impact management areas (groundwater‐surface water interaction and recharge areas) and river rehabilitation areas. The proposed river selections would achieve the biodiversity targets of 33 (66%) of the 50 river types; feasible rehabilitation would increase this to 92%. The greatest groundwater‐surface water interaction and recharge (30 to > 50 mm^?1) values are concentrated around the mountainous regions of the Little Karoo. This is because the main aquifers in the mountains, table mountain group (TMG) quartzites, yield naturally good quality water for human consumption. River reaches of unacceptable surface water quality were classified as degraded water resource delivery areas where the poor water quality was primarily due to saline return flows from irrigation and the impacts of other anthropogenic activities including abstraction of freshwater which otherwise would have diluted the return flows. Only the middle reaches of the Gouritz and Groot Rivers represent a possible win–win situation for both the environment and human use. Copyright © 2010 John Wiley & Sons, Ltd.     

河流健康诊断与生态修复

河流生态修复的总体目标是恢复河流健康，实现人与河流的和谐共存。从河流系统诸功能与河流健康之间的关系出发。分析了河流系统平衡的特征和影响因素，初步建立了河流健康诊断指标体系。根据河流受损功能、受损程度及其可修复性。提出了不同阶段河流治理和生态修复的对策。目前采用的主要技术包括：缓冲区修复、植被恢复、河道补水、生物-生态修复、生境修复、水生生物群落修复技术等。河流生态修复是一个多目标、多变量、多层次、多约束条件的动态优化问题，需要因地制宜、全面考虑、科学决策。     

深圳市西沥水库生态河道的构建技术与原理

汇入深圳市西沥水库的河流,因周围农业和生活污水的排入导致河流水质污染严重,严重影响了西沥水库的水质质量。本文介绍了生态河道修复目标及理念,采用生态河道技术修复功能退化河流的方法与原理。     

论河流生态修复

本文以河流系统诸功能与河流健康之间的关系为主线，从人与河流关系的发展与变化出发，探讨了原始自然阶段、工程控制阶段、污染治理阶段和河流生态系统修复和改善等四个阶段的河流特点和治理条件，分析了各个阶段河流系统平衡的特征和影响因素，初步建立了河流健康诊断指标体系，提出了河流生态修复的主要原则。河流生态修复的总体目标是恢复河流系统健康，实现人与河流的和谐共存。河流生态修复主要技术包括：缓冲区修复、植被恢复、河道补水、生物-生态修复、生境修复、水生生物群落修复技术等。本文采用层次分析法的基本思想，探讨了河流健康、河流功能、功能要素和生态修复措施四个层次的关系，同时指出了实现河流生态修复的步骤。     

The Economic Value of Allocating Water to Post-Mining Lakes in East Germany

This paper reports a contingent valuation study to value the economic benefits of a post-mining lake-district in East Germany. Lusatia Region faces serious water scarcity problems as the closure of mining pits in 1990 led to the termination of groundwater discharge into rivers. The water conflict centres around traditional water users whose water demand is no longer met and the rehabilitation of mining pits in form of a new lake-district. Current water allocation policy for the Elbe catchment places lowest priority on filling mining pits with river water, even though freshwater is essential for good lake water quality. Commissioned by the government, this study aims to determine the non-market benefits that would be generated by good water quality in the lake-district in order to re-assess the distribution of water among all water users in the Elbe catchment. Our findings show that the annual non-market benefits of the lake-district is significant and lies between 10.4 and 16.2 million euros. Apart from recreational benefits, people also obtain non-use values for the lake-district. Furthermore, two challenges for CV became apparent: fuzzy future benefits (potential improvement to the regional economy) significantly influenced WTP estimates, and WTP stated by users interviewed on site and at home varied significantly.     

河流生态流修复的新理念和目标

混凝土“包”起来的河道治理工程导致城市河流自我净化能力降低。目前我国河流治污项目多偏重修复受污染的水体,注重水质的改善,而不强调河流生态系统结构、功能的修复。提出河流生态修复的新理念和目标,并指出,为顺利开展河流生态修复实践,我国需要在理论、技术、水利工程设计规范、水法等方面进行的研究工作。     

刘树坤访日报告:大坝建设中的生态修复(六)

在水利工程特别是大坝建设中,生态环境必然遭到一定程度的破坏。为了避免和减轻对生态环境的影响,应当 在大坝建设的同时考虑和进行生态恢复,即保护生态恢复源、建立生态恢复模型和制订科学合理的生态恢复规划。     

大型灌区灌溉用水有效利用系数比较分析

从纵向和横向两个角度对比分析大型灌区节水改造对灌溉用水有效利用系数的影响。在横向上,跟踪和调研分析实施大型灌区续建配套和节水改造以来。6个典型大型灌区节水改造实施情况和灌溉用水有效利用系数变化情况,比较研究了灌溉用水有效利用系数提高的规律;在纵向上,以宁夏青铜峡灌区和卫宁灌区为例,详细分析了1991—2007年灌区灌溉用水有效利用系数变化过程,剖析了主要影响因素．最后提出了提高大型灌区灌溉用水有效利用系数的对策措施。     

Development of a Decision Making Support System for Efficient Rehabilitation of Sewer Systems

The main objective of sewer rehabilitation is to improve its function while eliminating inflow/infiltration (I/I). If we can identify the amount of I/I for an individual pipe, it is possible to find the distribution of the total I/I over the entire sewer system. With this information we identify which sub-area is more critical than others. However, in real, the amount of I/I for an individual pipe is almost impossible to be obtained due to the limitation of cost and time. For this reason, we suggested the rehabilitation weighting model (RWM) to determine it objectively or systematically. Based on the determined amount of I/I for an individual pipe, we also suggested the rehabilitation priority model (RPM), which is equipped with genetic algorithm, to determine the optimal rehabilitation priority (ORP) for sub-areas in term of minimizing the amount of I/I occurring while the rehabilitation process is performed. The benefit obtained by implementing the ORP for rehabilitation of sub-areas is estimated by the only waste water treatment cost (WWTC) of I/I which occurs during the sewer rehabilitation period. A decision making support system which is consisted of the RWM and the RPM was applied to an urban drainage area. The results of the ORP were compared with those of a numerical weighting method (NWM) and the worst order which are other methods to determine the rehabilitation order of sub-areas in field. The ORP reduced the WWTC by 22% compared to the NWM and by 40% compared to the worst order.