Selecting Portfolios of Water Supply and Demand Management Strategies Under Uncertainty—Contrasting Economic Optimisation and ‘Robust Decision Making’ Approaches

Planning appropriate portfolios of new water supplies and demand management measures requires considering a wide array of options and their interactions over a largely unknown future. Various modelling-assisted approaches are available to help this planning process. This paper applies two such frameworks to the UK’s Thames water resource system and compares their methods and outputs: how they consider uncertainty, how they represent supply and demand management options, and what plans each recommends. The first method is the current England and Wales industry standard: annual least-cost capacity expansion optimisation over a 25 to 30 year time horizon considering capital, operating (fixed and variable), social and environmental costs. The second approach uses stochastic simulation and regret analysis to select a preferred alternative, then statistical cluster analysis to identify causes of system failure enabling further plan improvement. When applied iteratively with system planners this second approach is referred to as Robust Decision Making (RDM). The economic optimisation approach considers all plausible combinations of supply and conservation schemes and recommends the least-cost schedule of their implementation. Our RDM application considers a smaller number of options but makes a more detailed assessment of the effect of uncertainty (supply, demand and energy price uncertainty were considered) on multiple criteria of system performance. The simulation-based approach also enables more realistic interaction amongst supply and demand management schemes. Both approaches recommended different plans which we explain by discussing the benefits and limitations of each. Joint application is recommended to produce least-cost plans that are robust considering multiple criteria of performance across a wide range of futures.     

A flexible modelling environment for integrated urban water harvesting and re-use

The steady increase of urban population and the possible effects of climate change that may adversely affect the amount of water available in current water supply systems, makes the study of stormwater and rainwater harvesting and wastewater recycling a high priority. The basic proposition is that any system of water supply that can reduce the amount of water drawn from main reservoirs will be of benefit to the whole supply region especially in terms of drought security. This paper describes a versatile modelling framework which can simulate a wide variety of combinations of centralised and decentralised Integrated Urban Water Management schemes from the allotment to the whole suburb scale. The framework combines two modelling approaches. The first, called urbanCycle, simulates water supply and demand, stormwater and wastewater using allotments as the basic building block. Although urbanCycle can simulate processes in great detail, it assumes that the network forms a directed acyclic graph. This simplifies the connectivity logic but precludes investigation of systems with decentralised storage, feedbacks and multiple supply paths. To overcome this, a second model, called urbanNet, based on network linear programming, is embedded in the urbanCycle framework to enable the modelling of recycling and harvesting options, as well as on-the-fly supply and demand decision making, based on objectives rather than pre-set operating rules.     

Water Resources Management Strategies for Adaptation to Climate-Induced Impacts in South Africa

This paper focuses on the development of a framework for strategy considerations for water resources management in South Africa to meet the development goals in the municipal and agricultural sectors. The north western part of South Africa experiences severe periods of drought and according to the climate change projections, will be most vulnerable to future climate induced water supply stress. A framework for selecting appropriate strategies is presented. A series of potential adaptation strategies most suitable for long term adaptation are discussed. These include both supply and demand side strategies. Barriers and obstacles to implementing these strategies include human and financial resource deficiencies at local municipal and community levels.     

Managing Water Resources to Adapt to Climate Change: Facing Uncertainty and Scarcity in a Changing Context

Some of the most significant future efforts in water resources management will be devoted to climate change adaptation. Climate change adaptation is of special concern in regions facing water scarcity where water management is already challenged by many problems. This paper is a review of current knowledge on approaches to address water issues under uncertainty in water-scarce regions, identifying specific policy actions for climate change adaptation. The focus is on regions, like the Mediterranean, California or Australia, where water resources are well developed and have become an essential part of socioeconomic activities but are currently facing significant challenges due to their dependence on water availability to maintain living standards. We provide an overview of the expected impacts of climate change on water resources and discuss management responses based on peer-reviewed studies published over the past three decades. The adaptation choices cover a wide range of options, from adaptive demand management to utilization of remaining marginal water sources. The intensification of successful measures already applied in the past is still viewed as a solution to reduce climate impacts. However, the emphasis is progressively being placed on sustainability, developing and extending the water management paradigm to include not only technical and economic criteria, but also ecological and social considerations.     

Adaptation of urban water supply infrastructure to impacts from climate and socioeconomic changes: The case of Hamilton,New Zealand

While the relations between climate variables and sectoral water demand have been well established in the literature, few studies have attempted to quantify changes in urban water usage with climate change. Concentrating on the city of Hamilton, New Zealand, we investigate possible water use and infrastructure needs for a range of climate and population projections. We find that water demand (at the monthly aggregate level) is largely driven by changes in population, and not significantly affected by changes in climate. However, as population increases, the effect of climate variables on per capita consumption will be magnified. Monthly aggregate changes may further mask potenially significant short-term shortages. In several scenarios, water supply shortages in 2030 occur with a 30--40% probability, suggesting needs for long-term capacity expansion or aggressive demand side management, rather than implementation of short-term management of water demand.     

需求侧水资源配置管理模式

随着经济发展及城市化水平的不断提高,社会对水资源的需求量大幅度增加,供需矛盾日益突出。通过需求侧管理(DSM)模式的全面分析,探讨将需求侧管理模式最小和费用最有效原则和综合资源规划(IRP)引入水资源管理,加强水资源需求侧管理,控制需求增长,将有利于水资源需求和供应相适应,实现水资源的可持续利用。     

Sustainable Water Supply and Demand Management in Semi-arid Regions: Optimizing Water Resources Allocation Based on RCPs Scenarios

Climate as one of the key factors in water resources management affects the amount of water in the hydrological cycle, which subsequently impacts the level of water availability. Considering the challenges that the South Alborz Region, Iran is currently facing in supplying water for various consumers; in this study, the climate change adaptation scenarios are investigated for sustainable water supply and demand. This study uses a procedure in which five different adaptation approaches, under RCPs scenarios, were established using the WEAP model to assess the impacts of various adaptation strategies on increasing the balance between water supply and demand over current and 2020s accounts. The findings suggest an imbalance between supply and demand in the current situation with the greatest imbalance in domestic use while the minimum in the industrial sector. The results of assessing adaptive scenarios show that various scenarios have different effects on balancing the water supply and demand by different consumers; on the other hand, the scenarios that directly affect domestic water demand have the greatest effect on minimizing the gap between supply and demand in the region; therefore, the options for decreasing the population demand along with diminishing the losses in the domestic water distribution network are the most effective alternatives for balancing supply and demand under all of the climate scenarios. The findings of this research indicate that adaptive management with the focus on restricting demand helps actively management of water resources in the regions with scarce water resources.

     

Integration of seawater and grey water reuse to maximize alternative water resource for coastal areas: the case of the Hong Kong International Airport

Development, population growth and climate change have pressurized water stress in the world. Being an urbanized coastal city, Hong Kong has adopted a dual water supply system since the 1950s for seawater toilet flushing for 80% of its 7 million inhabitants. Despite its success in saving 750,000 m(3)/day of freshwater, the saline sewage (consisting of about 20-30% of seawater) appears to have sacrificed the urban water cycle in terms of wastewater reuse and recycling. Can seawater toilet flushing be applied without affecting the urban water cycle with respect to sustainable water resource management? To address this issue, we examined the entire urban water cycle and developed an innovative water resource management system by integrating freshwater, seawater and reclaimed grey water into a sustainable, low-freshwater demand, low-energy consumption, and low-cost triple water supply (TWS) system. The applicability of this novel system has been demonstrated at the Hong Kong International Airport which reduced 52% of its freshwater demand.     

吉林省西部水资源开发利用战略探讨

吉林省西部地区气候属温带大陆性气候区，降水量少，降水年际变化很大，年内分配不均，为全省蒸发量最大区域。文章从建设节水高效的现代灌溉农业和现代旱地农业的用水战略，保证生态环境用水的水资源配置战略，需水管理为基础的水资源供需平衡战略，几个方面论述了吉林省西部地区水资源开发利用战略。     

A Financial,Environmental and Social Evaluation of Domestic Water Management Options in the West Bank,Palestine

Water is one of the most valuable natural resources in the West Bank, Palestine. Due to its limited availability, it is a resource that needs particular protection. Although agriculture consumes most of the water (70%) in the West Bank, the domestic water supply is strategically not less important. It is the aim of this study to evaluate domestic water management options suitable for Palestinian conditions that contribute to achieving water sufficiency in the domestic water use in the house of tomorrow. A number of options were evaluated economically, environmentally and socially using the concept of life cycle impact assessment (LCIA). Results of the study showed that by introducing a combination of domestic water management options, a substantial decrease in the water consumption of more than 50% can be achieved, thereby reducing the pressure on the scarce water resources. The annual environmental impact of the in-house water use can be reduced in the range of 8%, when using low-flow shower head to 38% when using rainwater harvesting systems. Some of the options (faucet aerators, low-flow shower heads and dual flush toilets) were found to be financially attractive with a pay back period of less than their expected lives, others (rainwater harvesting, graywater reuse and dry toilets) were found to be financially unattractive because of the high investment. In the social context, it was found that introducing such options can improve the quality of life of those not having enough water. There is already a popular willingness to take part in water conservation in the domestic sector in the West Bank. The strongest driving force for using water conservation measures is the awareness that water is a scarce resource. It was concluded that, theoretically, the house of tomorrow can be largely independent in terms of water and sanitation. Education and awareness campaigns in the context of water management with a focus on non-traditional options are key to achieve such a house.     

Future Water Supply and Demand Management Options in the Athabasca Oil Sands

The Athabasca River Basin, home to Canada's growing oil sands mining industry, faces challenging trade‐offs between energy production and water security. Water demand from the oil sands mining industry is projected to increase as climate change is projected to alter the seasonal freshwater supply. In this study, a range of water management options are developed to investigate the potential trade‐offs between the scale of bitumen production and industry growth, water storage requirements, and environmental protection for the aquatic ecosystems, under projections of mid‐century climate change. It is projected that water storage will be required to supplement river withdrawals to maintain continuous bitumen production under the impacts of future climate warming. If high growth in future bitumen production and water demand is the priority, then building sufficient water storage capacity to meet industry demand will be comparable to a week of lost revenue because of interrupted production. If environmental protection is prioritized instead, it will require over nine times the water storage costs to maintain water demand under a high industry growth trajectory. Future water use decisions will need to first, determine the scale of industry and environmental protection, and second, balance the costs of water storage against lost revenue because of water shortages that limit bitumen production. This physically based assessment of future water trade‐offs can inform water policy, water management decisions, and climate change adaptation plans, with applicability to other regions facing trade‐offs between industrial development and ecosystem water needs. Copyright © 2016 John Wiley & Sons, Ltd.     

Rainwater harvesting--an alternative for securing food production under climate variability.

Food insecurity is still a challenge in some remote and mountainous areas in China. When studying the impact of climate variability on food production, we should pay even more attention to the rainfed area. This is because the larger part of agriculture is the rainfed one and climate variability has more negative impacts on the rainfed agriculture than on the irrigated one. The traditional dry farming practices based on the principle of storing as much rain in the soil as possible and making best use of soil water could not bridge the gap between the time that the corp needs water and the time that rain occurs, so its effects on enhancing food production under climate variability is limited. Combining artificial water supply from rainwater harvesting systems with the traditional dry farming practices is an innovation in water management in rainfed agriculture. Experiences in the recent two decades indicate that rainwater harvesting irrigation can well mitigate the drought caused by the climate variability and bring the rainfed agriculture to a new level.     

Water balance modelling of alternate water sources at the household scale

Alternate water sources are being implemented in urban areas to augment scheme water supplied by a water utility to homes. These sources include residential wells, rainwater tanks and greywater systems. Greater water efficiency can be achieved when these systems are designed to match a water source to a given demand based on both water quantity and quality parameters. In this way the use of an alternate water source can be maximised and the use of the high quality scheme water minimised. This paper examines the use of multiple alternate water sources sequentially to supply the same demand point potentially optimising the use of all available water sources. It also allows correct sizing of such water systems and their components to reduce scheme water demand. A decision support tool based on water balance modelling was developed that considers such water options at the household scale. Application of this tool to eight scenarios for both large and small house lots shows that using alternate water sources individually can result in significant scheme water savings. However by integrating these sources additional scheme water saving can be made.     

Performance Analysis of a Communal Residential Rainwater System for Potable Supply: A Case Study in Brisbane, Australia

Cities in developed countries have increasingly adopted rainwater tanks as an alternative water source over the last 15 years. The rapid uptake of rainwater tanks has been driven by the need to reduce demand for centralised water services that are under pressure to adapt to population growth and climate change impacts. Rainwater tanks are part of integrated urban water management approach that considers the whole water cycle to provide water services on a fit for purpose basis that minimises the impact on the local environment and receiving waters. Rainwater tanks are typically applied at the household scale for non-potable water source uses such as toilet flushing and garden irrigation. However, this paper reports on a communal approach to rainwater harvesting, where the water is treated for potable use. A communal approach to rainwater harvesting can offer benefits, such as: economies of scale for capital costs, reduced land footprint, centralised disinfection and flexibility in matching supply and demand for different households. The analysis showed that the communal approach could provide a reliable potable water source to a small urban development. However, there was an energy penalty associated with this water source compared to centralised systems that could be addressed through more appropriate pump sizing. The outputs from this monitoring and modelling study demonstrated rainwater harvesting can be expanded beyond the current mainstream practices of household systems for non-potable use in certain development contexts. The analysis contained in this paper can be used for the improved planning and design of communal approaches to rainwater harvesting.     

Climate Change Impacts on the Water Supply System in the Warta River Catchment,Poland

The effects of a non-station ary climate on a water management system in the Warta River Catchment in Central Poland which already suffers from seasonal water deficits are exam ined in this paper. To determine a range of possible implications of global change on the region of interest, two scenarios were selected for the study: the warm-dry scenario predicted by the GFDL model, and warm scenario obtained from the GISS model. It is shown that the basin's water supply and demand are both sensitive and vulnerable to clim atic changes. Possible adaptation options to cope with further degradation of domestic, industrial and agricultural water supplies are recommended.     

Visualising a Stochastic Model of Californian Water Resources Using Sankey Diagrams

This paper describes a novel approach to the analysis of supply and demand of water in California. A stochastic model is developed to assess the future supply of and demand for water resources in California. The results are presented in the form of a Sankey diagram where present and stochastically-varying future fluxes of water in California and its sub-regions are traced from source to services by mapping the various transformations of water from when it is first made available for use, through its treatment, recycling and reuse, to its eventual loss in a variety of sinks. This helps to highlight the connections of water with energy and land resources, including the amount of energy used to pump and treat water, the amount of water used for energy production, and the land resources that create a water demand to produce crops for food. By mapping water in this way, policy-makers can more easily understand the competing uses of water, through the identification of the services it delivers (e.g. sanitation, food production, landscaping), the potential opportunities for improving the management of the resource and the connections with other resources which are often overlooked in a traditional sector-based management strategy. This paper focuses on a Sankey diagram for water, but the ultimate aim is the visualisation of linked resource futures through inter-connected Sankey diagrams for energy, land and water, tracking changes from the basic resources for all three, their transformations, and the final services they provide.     

北京市雨水利用政策体系研究

北京水资源严重匮乏,加大城市雨水利用对缓解水资源供需矛盾意义重大。分析了北京市雨水利用现状、利用潜力,回顾了2000年至今北京市雨水利用政策现状的发展历程,并对现有政策体系进行剖析,结合国外雨水利用的管理政策体系,从四方面提出北京市雨水利用政策建议。法律上要尽快建立全国性或全市性的法律法规;技术上要加快雨水利用相关技术标准的制定和修订工作;经济上需制定相关的经济补偿或奖励措施;管理上应建立统一职能管理部门。     

北京市雨水收集利用蓄水池容积计算与分析

基于北京市1984—2013年的日降雨资料,以北京林业大学林业楼及其周边绿地为研究区,设置3种用水情景(冲厕、绿地灌溉及冲厕+绿地灌溉),采用连续模拟法,分别绘制3种用水情景下雨水收集利用工程的雨水截留率、自来水替代率、供水保证率以及效益费用比变化曲线,并通过综合分析这些曲线的变化特征确定雨水蓄水池最佳设计容积(60~82 m3)。同时采用设计暴雨法计算1~5年不同重现期的蓄水池设计容积(77~248 m3)。结果表明,连续模拟法计算过程相对复杂,但可用于综合衡量雨水收集利用工程的雨洪管理效益,以及缓解水资源短缺效益、供水可靠性及经济可行性分析。     

The Use of System Dynamics Model to Enhance Integrated Resources Planning Implementation

Elsinore Valley Municipal Water District (EVMWD), like many other water agencies in southern California, relies heavily on imported water supply. The uncertainty associated with reliable imported water supplies due to drought conditions and climate change, and the increasing cost of imported water are areas of concern for EVMWD. Considering these conditions, EVMWD, which serves one of the fastest growing regions within Riverside County, embarked upon the development of its first Integrated Resources Plan (IRP) – a long term strategy for providing reliable water supplies to its growing customer base. The IRP’s evaluation methodology consists of three steps: Identification of potential water supply projects, project evaluation, and recommendation of a water supply portfolio comprised of the specific projects. A System Dynamics (SD) Water Resources Decision Support System (WRDSS) was used to evaluate different scenarios and examine EVMWD’s vulnerability to risks such as water supply shortage, and changes to water quality and/or water demand projections. Even though SD has been extensively applied to many water resources planning modeling efforts, based on our literature review, there is not a documented case of SD modeling applied to an IRP project. The recommended water supply portfolio represents the most cost effective option. It meets the forecasted long term deficit and provides the best reliability while providing good quality water supplies to EVMWD’s customers. The recommended water supply portfolio will be implemented using an adaptive management approach to adjust to changing conditions, coupled with long-range resource management policies that optimize water supply and storage assets in times of both drought and surplus.