A decision support tool for sustainable planning of urban water systems: Presenting the Dynamic Urban Water Simulation Model

Population growth, urbanisation and climate change represent significant pressures on urban water resources, requiring water managers to consider a wider array of management options that account for economic, social and environmental factors. The Dynamic Urban Water Simulation Model (DUWSiM) developed in this study links urban water balance concepts with the land use dynamics model MOLAND and the climate model LARS-WG, providing a platform for long term planning of urban water supply and water demand by analysing the effects of urbanisation scenarios and climatic changes on the urban water cycle. Based on potential urbanisation scenarios and their effects on a city's water cycle, DUWSiM provides the functionality for assessing the feasibility of centralised and decentralised water supply and water demand management options based on forecasted water demand, stormwater and wastewater generation, whole life cost and energy and potential for water recycling. DUWSiM has been tested using data from Dublin, the capital of Ireland, and it has been shown that the model is able to satisfactorily predict water demand and stormwater runoff.     

Estimating the impacts of climate change and urbanization on building performance

Over the past 15 years, much scientific work has been published on the potential human impacts on climates. For their Third Assessment Report in 2001, the United Nations International Programme on Climate Change developed a set of economic development scenarios, which were then run with the four major general circulation models (GCM) to estimate the anthropogenesis-forced climate change. These GCMs produce worldwide grids of predicted monthly temperature, cloud, and precipitation deviations from the period 1961–1990. As this period is the same used for several major typical meteorological year data sets, these typical data sets can be used as a starting point for modifying weather files to represent predicted climate change. Over the past 50 years, studies of urban heat islands (UHI) or urbanization have provided detailed measurements of the diurnal and seasonal patterns and differences between urban and rural climatic conditions. While heat islands have been shown to be a function of both population and microclimatic and site conditions, they can be generalized into a predictable diurnal and seasonal pattern. Although the scientific literature is full of studies looking at the impact of climate change driven by human activity, there is very little research on the impact of climate change or urban heat islands on building operation and performance across the world. This article presents the methodology used to create weather files which represent climate change scenarios in 2100 and heat island impacts today. For this study, typical and extreme meteorological weather data were created for 25 locations (20 climate regions) to represent a range of predicted climate change and heat island scenarios for building simulation. Then prototypical small office buildings were created to represent typical, good, and low-energy practices around the world. The simulation results for these prototype buildings provide a snapshot view of the potential impacts of the set of climate scenarios on building performance. This includes location-specific building response, such as fuel swapping as heating and cooling ratios change, impacts on environmental emissions, impacts on equipment use and longevity comfort issues, and how low-energy building design incorporating renewables can significantly mitigate any potential climate variation. In this article, examples of how heat island and climate change scenarios affect diurnal patterns are presented as well as the annual energy performance impacts for three of the 25 locations. In cold climates, the net change to annual energy use due to climate change will be positive – reducing energy use on the order of 10% or more. For tropical climates, buildings will see an increase in overall energy use due to climate change, with some months increasing by more than 20% from current conditions. Temperate, mid-latitude climates will see the largest change but it will be a swapping from heating to cooling, including a significant reduction of 25% or more in heating energy and up to 15% increase in cooling energy. Buildings which are built to current standards such as ASHRAE/IESNA Standard 90.1-2004 will still see significant increases in energy demand over the twenty-first century. Low-energy buildings designed to minimize energy use will be the least affected, with impacts in the range of 5–10%. Unless the way buildings are designed, built, and operated changes significantly over the next decades, buildings will see substantial operating cost increases and possible disruptions in an already strained energy supply system.     

Modeling the reduction of urban excess heat by green roofs with respect to different irrigation scenarios

Urban heat reduction by evaporative cooling from extensive green roofs is explored by applying irrigation scenarios to green roofs located in different climate zones using a coupled atmosphere-vegetation-substrate green roof model. The model,which is integrated in the building energy simulation software Energy Plus,is validated with eddy covariance surface energy fluxes from a green roof in Berlin,Germany. The original model wasmodified to include interception and an improved runoff calculation. Three irrigation scenarios were defined( no irrigation,sustainable irrigation by harvested runoff water,unrestricted irrigation) to study the heat reduction potential in terms of surface energy partitioning and sensible heat fluxes( QH). The irrigation scenarios are compared to two white roofs( albedo equal to 0. 35 and 0. 65) and a black roof.High correlation of sensible and latent heat( QE) fluxes between measured and modelled data for the original and the modified version of the green roof model were observed( for the original model,R~2= 0. 91 and 0. 81 for QH and QE,respectively,while for the modified version R~2= 0. 91 and 0. 80,respectively). The modified version was applied to study irrigation,due to lower systematic errors for QH,QEand better performance for the substrate moisture content. In comparison to a black roof the green roof reduces urban excess heat by 15%-51%with sustainable irrigation,by 48%-75%with unrestricted irrigation,but drops to 3% for unirrigated roofs in the different cities. Sustainable irrigation can be effective in climates with high annual( or summerly) precipitation.     

基于CMIP6的多情景上海雨洪风险 时空格局评价及规划响应对策

气候变化带来的雨洪灾害是城市发展的巨大挑战之 一,评估城市未来的雨洪风险并开展有效的规划应对是目前城 市发展的重大需求。未来气候情景下上海极端降水的时空格局 还未得到充分研究。利用第六次耦合模式比较计划(CMIP6) 中12个全球模式气候数据耦合上海市10个气象站点历史数 据,选用Delta降尺度方法预测上海市SSP245、SSP585 情景下的2025—2055和2070—2100年重现期为5、10、 20、50、100年的降水。使用SCS-CN模型模拟得到了多情 景下上海市径流深度,结果表明21世纪末期比21世纪中期最 大径流深度最高增加100%。结合各区域排水能力,划分了上 海市多情景下的雨洪风险等级。结果表明,上海市中心城区排 涝标准较高,雨洪风险较低,而中心城区以外区域风险相对较 高。针对不同风险等级区域,从流域视角统筹城市雨洪设施建 设,合理布局,提出防洪、除涝、雨水排水相互协调的规划响 应对策。     

Exogenous pressures and probabilistic assessment of risk and vulnerability of urban water systems in Ghana

ABSTRACT

Risk and vulnerability assessment of urban water systems can be extended to include several components. This work formulates a probable quantitative assessment of risk and vulnerability of urban water system based on climatic conditions and urban population growth. Climate change scenarios and population projections are used to estimate susceptibility to water supply systems’ risk and vulnerability. Quantile regression was used to establish the exponent correlation between the climate variables and population; and evaluate their consequential influences on urban water supply systems. We complemented the analysis with a probabilistic model to assess the robustness of urban water system that depends wholly on the climate for freshwater source. The study established that Climatic conditions, though uncertain, point to freshwater deficiency in the future. Moreover, population trends project a higher urban population thereby increasingly lowering water per capita and subsequently leading to doubtful urban water system’s resilience to the exogenous pressures.     

Becoming places: urbanism/architecture/identity/power,by Kim Dovey,London, Routledge, 2009, 204 pp., £25.99, ISBN 978-0-415-41637-5 (paperback), £95.00, ISBN 978-0-415-41636-8 (hardback)

Urban planning can contribute to reducing vulnerability to the impacts of climate change (including the expected increased occurrence of extreme weather events) in metropolitan areas. However, lack of urban governance and planning focusing on the metropolitan area as a whole, and decisions that do not take into account sufficiently the occurrence of such events, can substantially increase the cost of recovery from weather-related disasters. This policy study connects climate change adaptation, urban planning and metropolitan governance issues in the Hungarian context, focusing on the June 2010 floods in the town of Fels?zsolca, in the Miskolc metropolitan area. A review of key literature is provided on the impacts of climate change in cities and on governing climate action in metropolitan areas. Events leading up to and following the June 2010 Fels?zsolca floods are analysed from the perspective of urban planning. Based on evaluation criteria including effectiveness, cost-effectiveness, institutional capacity, transparency, political feasibility and time, four policy options are identified for climate action-related governance and planning in metropolitan areas, in the Hungarian context. Based on the above criteria, formalized horizontal partnerships between local authorities within the metropolitan area are chosen as the most favourable and currently most feasible policy option in Hungary.     

How gender disparities in urban and rural areas influence access to safe drinking water

Urban and rural populations face disparities in gender equality as well as access to safe drinking water, which have deleterious consequences for their well-being. Past studies highlight interdependencies between gender equality and sustainable water management, but they fail to account for effects of shifting urban and rural populations. We find that improved gender equality and access to safe drinking water are likely to persist within urban populations, and empowering women in urban areas could increase access to safe drinking water. Our research aims to enhance the understanding of sustainable provision of water under the circumstances of rapid urbanisation and climate change.     

Field simulation of urban surfaces runoff and estimation of runoff with experimental curve numbers

In this study, runoff responses of typical urban surfaces were investigated by scale models under artificial rainfall simulation, and the Soil Conservation Service (SCS) model was used to assess the impacts of land use changes and green infrastructures implementation on surface runoff of Beijing urban areas. The results showed that: Runoff coefficient of the impervious surface was about 2.1 times than that of the grassland. Time to runoff of the grassland was about 22.0 times that of the impervious surface. The concaved grassland, compared with the impervious surface, can significantly delay by 6.2 minutes the time to runoff, while the porous pavement significantly reduces 28.1% of the runoff coefficient. The runoff coefficient of Beijing urban areas increased from 0.68 in 2002 to 0.72 in 2012, due to the substantially increased impervious surfaces. The runoff coefficient decreased by 2.7%, 15.3% and 22.2% respectively under three green infrastructure scenarios.     

URBAS: forecasting and management of flash floods in urban areas

Recent studies on climate change indicate a growing frequency and intensity of flash flood events in western Europe. Flash floods are caused by extreme local precipitation. The URBAS project is concentrating on the urban occurrence of flash floods in Germany. URBAS has as a main objective to increase the preparedness and the range of possible actions of urban actors (e.g. communities, public enterprises) before and during rare small-scale flood events. Within URBAS the meteorological parameters, runoff and damage of flash floods are investigated. Innovative and feasible actions and precautionary measures at a reasonable cost-value-ratio are to be developed.     

Living with uncertainty: climate change,river flows and water resource management in Scotland

The recent increased variability of Scotland's hydroclimate poses major problems for water resource managers charged with making informed investment decisions given the likely impact of future climate change. Two strategies are developed in this paper to assist managers faced with this environmental uncertainty. The first involves trend analysis of precipitation and runoff since the 1960s and 1970s viewed against longer-term variability reported from instrumental records. The second strategy is based upon current climate change scenarios coupled with GCMs, and downscaling of precipitation and temperature to provide inputs to rainfall-runoff models. The long-term records of precipitation (back to the 1860s) and runoff (back to the 1930s) reveal the late 1980s and early 1990s as the wettest period on record for the west but not for the east. Over the period 1961-1996 the precipitation gradient has intensified across Scotland: wetter west; relatively dry east. Changes in runoff over the period 1970-1996 are also reported with increases in annual flows at 33 out of 38 stations (significantly at 12 stations) and decreases in low flows at 21 out of 38 stations (significantly at one station). The bulk of these flow increases occurred in the south and west especially in the autumn and spring. In terms of high flows over the period 1970-1996, four out of 44 stations reported a change in magnitude and 15 reported an increase in the frequency of POT events. In terms of future climate change, Hulme and Jenkins (1998) predict annual precipitation increases of 6-16% (Scotland) and 6-14% (Scottish Borders) from the 2020s to the 2080s based on the Hadley Centre model (HadCM2) medium-high scenario. Seasonal changes are concentrated in the autumn (SON) and winter (DJF) with increases as high as 24 and 29% for the autumn by the 2080s. (Arnell NW, et al. Institute of Hydrology Report No. 107, Wallingford, 1996), using an earlier transient Hadley experiment (IS92a), predict a 5-15% increase in annual runoff across Scotland by the 2050s, locally rising to 25%. Simulation flow duration curves for the 2050s generate Q95 values up by 5% or less (Rivers Don, Almond and Nith) and Q5 up by 10-24% (Rivers Don, Almond, Nith and Lyne Water). In terms of water resource planning, these predicted changes should be regarded as first order approximations, as they take no account of natural climatic variability, and could generate different absolute values if other scenarios were used. The predictions are, however, broadly consistent with trends in precipitation and runoff for Scotland since the 1970s. Major issues of concern to water resource managers are identified and commented upon in the light of these predictions.     

西北半干旱地区既有城市道路海绵化改造模式探索——以西宁为例

西宁属于西北高海拔半干旱地区,具有年均降雨量少、蒸发量高的气候特征.城市道路是城市径流雨水产流的主要组成部分.西宁现状城市道路均采用传统快排方式,存在雨水利用不佳、污染城市末端水系生态环境等问题.根据城市道路等级、下垫面及现状植被生长情况,分析西宁海绵城市建设试点区道路改造项目的 特点,定制城市道路海绵化改造的技术路线...     

Impact of urban geometry on outdoor thermal comfort and air quality from field measurements in Curitiba,Brazil

Urban climate can have severe impacts on people who use outdoor spaces within a city. In its essence, urban climate is directly linked to the configuration of street axes, building heights and their attributes. Thus, the role of urban planners can be crucial for guaranteeing outdoor thermal comfort and air quality in open spaces. This paper presents observed and estimated relations between urban morphology and changes in microclimate and air quality within a city center. Two approaches are presented, showing results of field measurements and urban climate simulations using the ENVI-met software suite. From measured microclimatic data and comfort surveys, carried out in downtown Curitiba, Brazil, the impact of street geometry on ambient temperatures and on daytime pedestrian comfort levels was evaluated, using the sky-view factor (SVF) as indicator of the complexity of the urban geometry. The impact of street orientation relative to prevailing winds and the resulting effects of ventilation (air speed and spatial distribution) on the dispersion of traffic-generated air pollutants were additionally analyzed by means of computer simulations. Results show the impact of urban geometry on human thermal comfort in pedestrian streets and on the outcomes of pollutant dispersion scenarios.     

Impacts of Climatic Change on River Flow Regimes in the UK

Much has been written in recent years about the potential threats posed by increasing greenhouse gas concentrations. This paper summarizes the implications of global warming for hydrological processes in general and river flow characteristics in the UK in particular, emphasizing the present high degree of uncertainty. Current climate change scenarios for the UK imply that rainfall between autumn and spring will increase, and this may have beneficial implications for UK water resources. However, the effect of this increase may be outweighed by higher evapotranspiration. Average annual runoff in a catchment in southern UK may be reduced by around 5% by the middle of the next century, but this estimate is very uncertain: runoff may reduce by 30% or increase by 30%. Runoff in northern and western UK is likely to show a slight increase (but with similarly large confidence intervals). It is probable that river flows in the UK will be much more concentrated in winter than at present. The effect of a given climate change scenario on monthly flow regimes depends on the current summer water balance and on catchment geological conditions.     

Spatial analysis of urban stormwater quality: Ramallah district as a case study, Palestine

Urban runoff pollution sources are formidable obstacles to achieving water source goals in numerous municipalities. Ramallah district currently holds one of the highest rates of urbanization in Palestine causing a significant increase in surface runoff. Consequently, this causes increased flooding and a significant decrease in water quality due primarily to the accumulation of pollutants. To date, most research has focused on specifying temporal variations of stormwater quality parameters that include high uncertainties and also increase the risk of pollution control structures' failure. Spatial variations of the runoff quality are the key factor in nonpoint source pollution studies. This research investigates the spatial variability of urban runoff quality parameters in relation to land use of urban catchments. The research estimated pollutant concentration for improved and efficient design of pollution control structures for each land use.     

Private initiatives in German urban development policy

Business Improvement Districts (BID) and Housing Improvement Districts (HID) are a new instrument of urban development policy in Germany. Their use reflects the fact that public assistance for urban development, while necessary, is not sufficient on its own to bring about the required change. They can be seen as a specific version of public–private partnership, which is to some extent also the philosophy underlying government-backed public assistance. Based on private initiative, they may be formalized (on the basis of legislation) or more informal. The first formalized German BID was established in Hamburg in 2005; a HID will follow soon. The Federal Ministry of Transport, Building and Urban Affairs has set up a scientific research initiative, Urban Improvement Districts in Urban Restructuring, with 14 model projects around Germany, on a more informal basis. The Ministry wants to learn how BIDs and HIDs will fit into legislation on, and give financial assistance to, urban development, as public engagement will increasingly reach its fiscal limits and the role of private initiatives in urban development will increase.     

Linked models to assess the impacts of climate change on nitrogen in a Norwegian river basin and FJORD system

Dynamically downscaled data from two Atmosphere-Ocean General Circulation Models (AOGCMs), ECHAM4 from the Max-Planck Institute (MPI), Germany and HadAm3H from the Hadley Centre (HAD), UK, driven with two scenarios of greenhouse gas emissions (IS92a and A2, respectively) were used to make climate change projections. These projections were then used to drive four effect models linked to assess the effects on hydrology, and nitrogen (N) concentrations and fluxes, in the Bjerkreim river basin (685-km(2)) and its coastal fjord, southwestern Norway. The four effect models were the hydrological model HBV, the water quality models MAGIC, INCA-N and the NIVA FJORD model. The downscaled climate scenarios project a general temperature increase in the study region of approximately 1 degrees C by 2030-2049 (MPI IS92a) and approximately 3 degrees C by 2071-2100 (HAD A2). Both scenarios imply increased winter precipitation, whereas the projections of summer and autumn precipitation are quite different, with the MPI scenario projecting a slight increase and the HAD scenario a significant decrease. As a response to increased winter temperature, the HBV model simulates a dramatic reduction of snow accumulation in the upper parts of the catchment, which in turn lead to higher runoff during winter and lower runoff during snowmelt in the spring. With the HAD scenario, runoff in summer and early autumn is substantially reduced as a result of reduced precipitation, increased temperatures and thereby increased evapotranspiration. The water quality models, MAGIC and INCA-N project no major changes in nitrate (NO(3)(-)) concentrations and fluxes within the MPI scenario, but a significant increase in concentrations and a 40-50% increase in fluxes in the HAD scenario. As a consequence, the acidification of the river could increase, thus offsetting ongoing recovery from acidification due to reductions in acid deposition. Additionally, the increased N loading may stimulate growth of N-limited benthic algae and macrophytes along the river channels and lead to undesirable eutrophication effects in the estuarine area. Simulations made by the FJORD model and the HAD scenario indicate that primary production in the estuary might increase up to 15-20%, based on the climate-induced changes in river flow and nitrate concentrations alone.     

Designing and calibrating an agent-based platform to evaluate the effect of climate variables on residential water demand

Many Iranian metropolises, including Shiraz, are situated in arid and semi-arid regions, lacking sufficient renewable water resources. In recent years, climate changes, including drought and rising temperatures, have led to changes in water supply and demand. Given the necessity and importance of urban water supply, this study investigates the impact of different climate scenarios on residential water demand. Many studies, in their models, do not consider the social interactions between household water consumers and the change in their consumption behaviour, which serves as a fundamental drawback. Thus, the present research attempts to propose an agent-based framework by modelling social interactions via the diffusion process to investigate water consumption behaviour efficiently. The model is calibrated and applied to Shiraz City in Iran, according to the data from 2006 to 2019, and it is used to simulate each scenario for the following years until 2032. The findings show that temperature has a positive and significant effect on residential water consumption; yet, rainfall negatively affects water consumption. The simulation results of these scenarios for temperature increase or decrease and rainfall changes are estimated. In addition, the developed agent-based platform can be easily calibrated and adjusted based on the data of any other city to simulate water demand estimation under different climatic and even economic scenarios. Urban water managers can benefit from such estimates to plan future infrastructure development and proactive management of seasonal water resources under the growing pressure of potential climate change because construing the sensitivity of seasonal water consumption to climate conditions is essential to respond to variations in demand.     

Drivers of urban sprawl in urban areas of Iran

During the recent decades, debates about urban sprawl have increased strongly in Iran. Literature review shows that there are few studies about causes of sprawl in urban areas of Iran. This paper analyses driving forces in creation or intensification of urban sprawl in Iranian cities. The methodology of the research is based on documentary and survey method. Results indicate that the most important drivers of urban sprawl are 22 factors in Iran. By using exploratory factor analysis, 22 factors are summarized in eight main factors. These factors include population growth, land value, political fragmentation, land speculation, transportation policies, exterior pressure, management system and land use. The eight main factors are able to explain an average of 76.9% of the urban sprawl phenomenon in Iran. The analysis of variance indicates that none of them can be effective in explaining urban sprawl alone in Iran that they were explained by each factor on urban sprawl. The population growth has the highest impact by 13% and land use has the lowest impact by about 7%. The margin of discrepancy between variance was explained by factors that suggest all of the eight extracted factors play a key role in the urban sprawl of Iran. Policies for controlling and reducing consequences of this phenomenon should be initiated by the government by considering the influential role of government in the urban sprawl of Iran. In particular, it can be helpful to establish integrated urban management, a compilation of comprehensive law about urban land and pay attention to worn-out textures and brownfield development.     

城市建设强度与热岛的相关性——以重庆市开州区为例

城市建设强度是城市热岛形成与演变的主要驱动因素,为了揭示两者之间的量化关系,以重庆市开州区为例,在用地地块、规则网格和建筑斑块3个空间尺度上,使用ArcGIS提取地表温度(LST)与建设强度指标,利用SPSS分析其相关性并构建多元回归模型。结果表明:用地地块尺度上,LST与绿化率、建筑密度和容积率之间均呈现显著的负相关,与建筑底面积和总建筑面积之间均呈现显著的正相关。规则网格尺度序列上,LST与建设强度各指标之间的相关性系数随网格面积的增大而增大,在840m网格时达到最大值;总体上LST与绿化率之间呈显著的负相关,与建筑密度和容积率之间呈显著的正相关。建筑斑块的尺度上,LST与建筑层数之间有显著的负相关关系,与总建筑面积之间有显著的正相关关系。城市建设强度直接或间接影响了城市热岛的形成与演变,而相关分析发现,建设强度指标并非都与LST之间呈正相关关系,这表明城市热岛除受建设强度的影响外,还受区域气候、城市形态、城市性质、交通方式以及建筑材质与色彩等多种因素的协同影响,是一个非线性的复杂过程。     

Mercury mobilization in urban stormwater runoff

Urban stormwater runoff has been identified as a leading cause of waterway impairment for many pollutants, but there has been a lack of research that directly measures Hg in urban stormwater runoff. The objectives of this research were: to use high frequency sampling to characterize the Hg export dynamics from an urban micro-catchment (i.e. a parking lot) during individual rain events; determine the relationship between suspended sediments and Hg transport; assemble event-scale mass balances of atmospheric Hg inputs, surface storage, and Hg export in runoff to evaluate the relative importance of rainfall-derived Hg and surface-derived Hg in runoff; and finally, to compare the yield of Hg from the urban micro-catchment to that of a larger mixed land-use urban catchment to evaluate the feasibility of scaling the results. The results found that the highest Hg concentrations in runoff were observed during the rising limb of the hydrograph (first flush effect), which was dominated by particulate bound Hg (84+/-8%). There was a significant relationship between the Hg and total suspended solids (TSS) concentrations in runoff. For all events, the largest Hg flux occurred during the period of peak discharge, even though the Hg concentrations were substantially lower during this period. The catchment surface Hg load (i.e. street dust) varied over the course of the study, but the changes were not clearly linked to the rain events. The mass balance of the Hg inputs and outputs from the catchment showed that it could act as a Hg sink or a source depending on the rainfall characteristics. The export of Hg from the larger mixed land-cover catchment were all within the range of the values from the parking-lot catchment, though tended to be lower as a result of increased retention and fewer sources/disturbance within the catchment.