Klimawandel und Urbanisierung – wie soll die Wasserinfrastruktur angepasst werden?

Conventional urban water servicing has successfully provided cities with clean water, sanitation and flood protection. Traditional approaches are unsuited to address future challenges like climate change and modern urban development trends (e.g. migration, aging population, densification). As well as increased risks of water scarcity and flooding, society's demands for urban amenity and healthy waterways in metropolitan areas also challenge these traditional principles of urban water management. It is increasingly recognized that solutions to these challenges will not be purely technological in nature; the socio-institutional contexts will also be critical. However modelling tools to support medium and long-term strategic planning of integrated social and infrastructural dimensions are lacking, leaving decision-makers with untested policy ideas. To identify possible transition strategies to a resilient city, the development of the DAnCE4Water (Dynamic Adaptation for eNabling City Evolution for Water) within the EU FP7 project “PREPARED: Enabling Change” as a strategic planning and decision-support tool is thus proposed. DAnCE4Water allows ‘What-if’ experiments by investigating possible consequences of policies and strategic actions, taking into consideration urban development, climate change, biophysical environment and societal dynamics. This paper presents the concept of the DAnCE4Water tool and its application to an example city's evolution 20 years into the future.     

Historical climate and stream flow trends and future water demand analysis in the Calgary region, Canada.

The city of Calgary has been one of fastest growing cities in Canada in recent years. Rapid population growth and a warming climate trend have raised concerns about sustainable water supply. In this study, historic climate, stream flow and population data are analyzed in order to develop models of future climate trends and river-water resource availability. Daily water demands for the next 60 years were projected using the relationship between daily maximum temperature and water demand under simulated climate and population growth scenarios. To maintain sustainable growth Calgary will require water conservation efforts that reduce per capita water use to less than half of the current level over the next 60 years, an interval when the civic population is expected to be doubled.     

Diffuse pollution abatement--a key component in the integrated effort towards sustainable urban basins.

Water bodies are highly stressed by overdrafts of water for many purposes upstream and in the cities, and effluent domination and excessive point and diffuse pollution downstream. Pollution is also caused by the urban landscape which prefers impervious rather than porous surfaces; fast-conveyance infrastructure rather than "softer" approaches like ponds and vegetation; and stream channelization instead of natural stream courses, buffers and floodplains, and development in the floodplains. In future, the comprehensive and complex problems of urban pollution must be solved within the framework of the total hydrological cycle concept. This provides a new impetus to diffuse pollution management in urban areas. The best management practices that have been developed in the past could become key components of the new urban total hydrological cycle paradigm for solving the water shortage and pollution problems in an integrated manner, and making the urban systems hydrologically and ecologically sustainable. The paradigm will include landscape changes (less imperviousness, more green space used as buffers and groundwater recharge) as well application of the best management practices that provide water conservation, storage and reuse.     

Climate Change and Water Resource Availability: An Impact Assessment for Bombay and Madras,India

ABSTRACT

Global climate change associated with rising atmospheric concentrations of greenhouse gases may alter regional temperature and precipitation patterns. Such changes could threaten the availability of water resources/Or rapidly growing Third World cities, many of which are already experiencing severe water supply deficiencies. This paper investigates the potential impacts of climate change on water resource availability for two Indian cities, Bombay and Madras. The paper begins by discussing future trends for population growth and water demand in each city. Nat, using climate change scenarios based on three general circulation models (GCMs), the paper assesses how climate change may affect water availability in the two urban regions. The assessment is conducted through the use of a monthly dryness index measuring potential evapotranspiration and precipitation. For each region, the dryness index under “normal” climatic conditions is compared with indexes created using GCM scenarios. The results of this assessment indicate that, unless large increases in regional precipitation accompany climate warming, higher rates of evapotranspiration will mean reduced water availability for both cities. The paper concludes by discussing some implications for water management in Third World cities.     

Economic assessment of climate adaptation options for urban drainage design in Odense, Denmark

Climate change is likely to influence the water cycle by changing the precipitation patterns, in some cases leading to increased occurrences of precipitation extremes. Urban landscapes are vulnerable to such changes due to the concentrated population and socio-economic values in cities. Feasible adaptation requires better flood risk quantification and assessment of appropriate adaptation actions in term of costs and benefits. This paper presents an economic assessment of three prevailing climate adaptation options for urban drainage design in a Danish case study, Odense. A risk-based evaluation framework is used to give detailed insights of the physical and economic feasibilities of each option. Estimation of marginal benefits of adaptation options are carried out through a step-by-step cost-benefit analysis. The results are aimed at providing important information for decision making on how best to adapt to urban pluvial flooding due to climate impacts in cities.     

Water Right Prices in the Rio Grande: Analysis and Policy Implications

Climate change, water supply limits, growing environmental values of water and worldwide population growth continue to raise the scarcity of water. These challenges have intensified the transfer of water from farms to cities. Water right transfers are an important international institution to stretch water supplies. In North America's Rio Grande Basin water right transfers are an especially important institution for meeting the growth in urban demands. Despite the importance of water right transfers as a social institution, sellers face uncertainty on the asking price, while buyers face similar uncertainty on the offer price. Weak information on water right prices stymies water transfers while limiting the future resilience of water transfers to address climate change and the need to cope with change in water supplies and demands. This paper describes the development of a database on water right prices using observed transactions from 1980 to 2007. An empirical model was developed using the data to identify important factors influencing those prices. Five water right price predictors were found to be significant: total regional urban water use, priority date of the water right, quantity of water rights offered for sale, regional reservoir storage volume, and regional farm income. Depending on the future status of food scarcity and urban water conservation programmes, water right prices in the basin could grow from zero to 27% over 2010–2020.     

碳中和愿景下城市供水面临的挑战、安全保障对策与技术研究进展

随着我国人口逐渐增多、经济迅猛发展、生活水平不断提高、城市化进程逐渐加速,城市面积扩大并发展成城市群,对水资源的需求持续增加.与此同时,工业、农业生产、人类活动等途径进入环境中的各类污染物总量也在增加、成分更加复杂,这些污染物最终进入城市水体.为满足水质要求,城市供水系统能源消耗逐渐增加,产生较多的碳足迹.一些城市群为...     

Spatial Optimization Models for Water Supply Allocation

Climate change is likely to result in increased aridity, lower runoff, and declining water supplies for the cities of the Southwestern United States, including Phoenix. The situation in Phoenix is particularly complicated by the large number of water providers, each with its own supply portfolio, demand conditions, and conservation strategies. This paper details spatial optimization models to support water supply allocation between service provider districts, where some districts experience deficits and others experience surpluses in certain years. The approach seeks to reconcile and integrate projections derived from a complex simulation model taking into account current and future climate conditions. The formulated and applied models are designed to help better understand the expected increasingly complex interactions of providers under conditions of climate change. Preliminary results show cooperative agreements would reduce spot shortages that would occur even without climate change. In addition, they would substantially reduce deficits if climate change were to moderately reduce river flows in Phoenix’s major source regions, but have little effect under the most pessimistic scenarios because there are few surpluses available for re-allocation.     

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.     

山地城市防洪标准评估及防洪能力提升的探讨——以南平为例

山地城市气候多变,区域内降雨时空变化大,地形复杂,同时受外洪、内涝、山洪的威胁,灾害叠加,复杂多样,城市的防洪能力迫切需要提升,然而单一通过提高防洪工程标准的做法并不能解决城市复杂的洪涝问题。本文以福建省南平市为例,利用水动力学模型,在科学评估山地城市防洪标准的基础上,通过上游蓄洪、下游分洪等综合工程措施,将受淹状态调控在可承受的范围之内,降低城区内河道水位0.38~0.97 m,有效提升了城市防洪能力。     

创建水生态文明城市的框架性构想

水是城市生存和可持续发展的根本保障,城市水生态系统也是支撑其他城市子系统存在和发展的基础与前提。采取"政府主导,市场参与,多部门介入,持续推动"的混合型推动模式,切实推动"城市水基础建设、城市水功能开发、城市水管理服务"三位一体的水生态横向业务板块,构建"供水系统、用水系统和排水系统"三位一体的水生态纵向流程板块,形成"水资源节约、水环境友好,水文化浓郁、水功能丰富,水管理有效、水服务优质"的城市水生态文明体系,把城市水资源建设开发成为城市的水资产,未来成为当代人留给子孙后代的水遗产。     

The Water-Economy Nexus: a Composite Index Approach to Evaluate Urban Water Vulnerability

Resource scarcity is a driving force behind water conservation and reuse as urban areas seek strategies to adapt to population growth and environmental challenges. Although there are numerous indicators that examine urban water resource and demand characteristics, these approaches do not tie together how aspects like economic health, environmental conditions, and population growth correlate with local water conservation to demonstrate a city’s ability to cope with water resource vulnerability. This research develops a conceptual framework for the Water-Economy Index (WEI) which characterizes social, economic, and environmental dynamics of water reuse and conservation. The application specifically utilizes a principal component analysis (PCA) to evaluate how hydro-economic indicators (including water demand intensity, demand for recycled water, economic productivity of water, unemployment, and allocations of water resources) are correlated and can impact sustainability goals. The PCA method aggregates indicators into three groups: socio-economic, water allocation, and socio-environmental indicators. The most influential indicators within each group are economic productivity of water, wastewater reuse, and consumptive water demand, respectively. The WEI ranks of 49 cities are compared to identify shared traits across individual indicators and to demonstrate the application of the WEI for benchmarking. The results provide insight into the complex relationship between the characteristics of an urban area’s water demand and socio-economic performance.

     

Managing Adaptation of Urban Water Systems in a Changing Climate

Current evidence is that climate change is occurring, it is largely manmade and it will have significant implications for human civilisation. Australia is particularly vulnerable to the anticipated effects of climate change, creating major challenges for water resource management and water supply security. Climate change adaptation offers a means by which we can reduce our exposure to future climate change risks, whilst at the same time exploiting any potential benefits that may arise from climatic changes. This review outlines the current major climate change adaptation challenges facing the water supply industry at large, with a particular focus on these challenges in an Australian context. It also aims to highlight the critical knowledge gaps and strategies required to assist in the formulation of adaptation responses to the range of potential impacts on water infrastructure and future water security. A diverse range of management and assessment techniques are used by relevant professions in industry. Here, an adaptive management approach is presented highlighting the important information required for robust assessment.     

The Added Value of Understanding Informal Social Networks in an Adaptive Capacity Assessment: Explorations of an Urban Water Management System in Indonesia

Social networks play an important role in environmental governance regimes, and they are a key to the adaptive capacity of systems that deal with complex, contextual and multi-faceted issues. Urban water systems are typical examples of complex systems facing many pressures, such as increased population, water quality deterioration, and climate change. This paper explores social networks of the key stakeholders engaged in urban water management, in Makassar City, Indonesia, in the context of exploring ways to improve management of an increasingly complex urban water system. Three social networks were explored; those constituted by formal and informal interactions and networks perceived by stakeholders to be “ideal”. Formal networks were identified through an examination of the legislative instruments and government agencies’ documents relating to water provision in Makassar, while the informal and “ideal” networks were investigated in collaboration with the stakeholders. The research found that the informal social network was more extensive than were the formally required networks, and the investigation of informal networks created a potentially more robust and adaptive water management system than would have occurred through inclusion of formal institutional arrangements. We suggest that in examination of the adaptive capacity of an urban water system, one also considers the informal arrangements and linkages, as this additional information about the system is necessary to enhance our understanding of potential adaptation of water management and improved urban water systems.     

Enhancing urban infrastructure investment planning practices for a changing climate.

Climate change raises many concerns for urban water management because of the effects on all aspects of the hydrological cycle. Urban water infrastructure has traditionally been designed using historical observations and assuming stationary climatic conditions. The capability of this infrastructure, whether for storm-water drainage, or water supply, may be over- or under-designed for future climatic conditions. In particular, changes in the frequency and intensity of extreme rainfall events will have the most acute effect on storm-water drainage systems. Therefore, it is necessary to take future climatic conditions into consideration in engineering designs in order to enhance water infrastructure investment planning practices in a long time horizon. This paper provides the initial results of a study that is examining ways to enhance urban infrastructure investment planning practices against changes in hydrologic regimes for a changing climate. Design storms and intensity-duration-frequency curves that are used in the engineering design of storm-water drainage systems are developed under future climatic conditions by empirically adjusting the general circulation model output, and using the Gumbel distribution and the Chicago method. Simulations are then performed on an existing storm-water drainage system from NE Calgary to investigate the resiliency of the system under climate change.     

Optimization of Retention Ponds to Improve the Drainage System Elasticity for Water-Energy Nexus

The purpose of this paper is to investigate the optimization of retention ponds for energy production by a low-head hydropower converter towards smart water grids and new flood adaptation solutions. Flood drainage systems are infrastructures essential in urban areas to control floods, which include retention ponds that can be used as innovative solutions adapted to climate changes and smart water grids to produce energy in a near future and to improve the drainage system elasticity. A catchment-scale water/energy management model is used for designing solutions by defining the characteristics of the urban area and the hydropower converters. The study area is based on Alcântara zone, in a district of Lisbon, a specific down-town zone close to the Tagus river, which has the backwater sea tidal influence. A solution based on the catchment of this area for extreme values of runoff induced by a significant climate changes event in these last years is analysed and then optimized in terms of energy production for different characteristic parameters. Finally, results are shown and discussed to reveal the most suitable solutions.     

Telecoupling in urban water systems: an examination of Beijing’s imported water supply

Urban centres increasingly have difficulties meeting water needs within their hydrologic basins. To sustain urban water supply, cities and water source regions have increased telecouplings (socio-economic and environmental interactions over distances). To analyse these complex interactions, we apply the new telecoupling framework to the water-stressed megacity of Beijing’s imported water supply. We found that Beijing’s remote water sources have lower risk than local supply, but connections impact the sending systems. The telecoupling framework provides a standard, systematic and flexible tool for evaluating the sustainability of urban water supply. It also identifies a number of research gaps for future quantification efforts.     

Blueprint for a greener city: growth need not cost the earth.

The current human use of global natural resources exceeds the long-term sustainable capacity of the planet. New and more sustainable ways of building cities and providing urban water services are needed. The Australian city of Sydney is expected to grow by more than 1 million people over the next 30 years. Water use from the Hawkesbury-Nepean River system already exceeds system capacity. Current proposals to allocate a greater proportion of low flows to meet environmental flow needs will limit urban water allocations and require the development of more efficient water and sewerage systems for new and existing urban development. This paper presents a hypothetical case study of how water supply and sewerage services might be provided for an additional 1 million people over a 25-year period. It compares traditional service provision with alternative scenarios incorporating water conservation measures, rainwater harvesting and water reuse. The paper presents both economic and environmental comparisons. The economic comparisons include valuations of environmental externalities in the form of environmental levies. It shows that the extra capital costs of water conservation, alternative water sources and water reuse scenarios are offset by operating savings and environmental benefits. Ecological footprints are reduced because of lower water diversions, discharges, energy use and CO2 emissions. The paper also discusses the implication of alternative infrastructure ownership and water pricing arrangements, and the opportunities to create incentives for additional investment in water conservation and reuse projects.     

Sustaining Urban Water Supplies in India: Increasing Role of Large Reservoirs

Urban water demand is rapidly growing in India due to high growth in urban population and rapid industrialization. Meeting this demand is a big challenge for the urban planners in India. Incidentally, the large urban areas are experiencing faster growth in population, and most of them are in arid and semi arid regions, which are naturally water-scarce. As a result, water supplies from local water resources including aquifers are falling far short of the high and concentrated demands in most urban areas. Under such situations, these large cities have to rely on distant large reservoirs. The analysis of 302 urban centers shows that cities with larger population size have much higher level of dependence on surface water sources. Also, greater the share of surface water in the city water supplies, higher was the level of per capita water supply. Multiple regression models are estimated for Class I cities and Class II towns in India. The results show that Population Elasticity of Water Supply (PEWS) change with time and space—for Class I cities it was 1.127 in 1988, whereas that with respect to 1999 population is 1.289. It also shows that Class I cities have better water supply (PEWS is 1.127 in 1988 and 1.289 in 1999) than Class II towns (PEWS is 0.396 in 1988 and 0.675 in 1999). Given the structure and pattern of urban population growth, economic conditions and water demands, large reservoirs will have a much bigger role in meeting urban water supply needs.     

Quantifying the Urban Water Supply Impacts of Climate Change

The difference in timing between water supply and urban water demand necessitates water storage. Existing reservoirs were designed based upon hydrologic data from a given historical period, and, given recent evidence for climatic change, may be insufficient to meet demand under future climate change scenarios. The focus of this study is to present a generally applicable methodology to assess the ability of existing storage to meet urban water demand under present and projected future climatic scenarios, and to determine the effectiveness of storage capacity expansions. Uncertainties in climatic forcing and projected demand scenarios are considered explicitly by the models. The reservoir system in San Diego, California is used as a case study. We find that the climate change scenarios will be more costly to the city than scenarios using historical hydrologic parameters. The magnitude of the expected costs and the optimal investment policy are sensitive to projected population growth and the accuracy to which our model can predict spills.