DETERMINISTIC MODELS FOR PREDICTING RESIDENTIAL WATER CONSUMPTION1

ABSTRACT: Forecasts of future urban water demand traditionally have been made by the projection of historic trends in per capita consumption and population. This paper outlines the use of two deterministic models to forecast the residential component of urban water demand. The models incorporate specific representation of the activities which result in water consumption at each residence. Predictions of water use can then be made by modeling the changes expected in the number of these activities and the consumption for each such activity.     

Using nighttime light data to estimate water evaporation inside buildings in China's urban areas

Urbanization has a great impact on urban evapotranspiration. Water evaporation inside buildings is an important part of urban water vapor resources and a crucial core of urban hydrological processes. The systematic studies on building water evaporation (BWE) are mostly the method of experimental monitoring. This study proposed a new method to simulate and estimate water evaporation flux inside buildings in urban areas. Based on the nighttime light data and urban per capita gross domestic product (GDP), a new modeling system was built to simulate the total BWE. Building area was calculated using the nighttime light data. And the BWE coefficient D_f was estimated according to the important indicator of economic development per capita GDP value. Then the water evaporation inside urban buildings and the spatial distribution of water evaporation inside buildings in typical cities could be obtained. The results showed that the total amount of water evaporation inside buildings in China's urban areas was 24.5 billion m³. Among the 31 provincial capitals in China, Shanghai had the largest BWE of 1.08 billion m³. The minimum water evaporation of buildings in Lhasa was 20.0 million m³. Studies of BWE can assess urban water budgets, support on-demand allocation of water resources, and provide a fundamental understanding of the relationship between water resources and energy heat island effects in urban areas.     

Efficiency evaluation for regional urban water use and wastewater decontamination systems in China: A DEA approach

Rapid economic growth and urbanization in China have resulted in great water consumption in recent years. China has been facing increasingly severe water shortage crisis, especially in urban areas. This paper focuses on performance analysis for regional urban water use and wastewater decontamination systems in China. To this end, a DEA-based approach is developed. In the proposed approach, the efficiency of the system is decomposed into water use efficiency and wastewater decontamination efficiency. In the wastewater decontamination sub-system, the purified wastewater (reusable water) is treated as a desirable output; while in the water use sub-system, it is incorporated as a fixed input, which cannot be decreased in the process of efficiency optimization. The efficiency of the system is defined as the average of the two sub-systems’ efficiencies. The proposed approach can find inefficiencies caused by the internal factors between sub-systems, which cannot be identified using the traditional DEA approaches. We finally apply the proposed approach to analyze the efficiencies of regional urban water use and wastewater decontamination systems in China. Based on the application results, some findings and implications for efficiency improvement of urban water management in China are achieved.     

Impact of Urban Sprawl on Water Quality in Eastern Massachusetts,USA

A study of water quality, land use, and population variations over the past three decades was conducted in eastern Massachusetts to examine the impact of urban sprawl on water quality using geographic information system and statistical analyses. Since 1970, eastern Massachusetts has experienced pronounced urban sprawl, which has a substantial impact on water quality. High spatial correlations are found between water quality indicators (especially specific conductance, dissolved ions, including Ca, Mg, Na, and Cl, and dissolved solid) and urban sprawl indicators. Urbanized watersheds with high population density, high percentage of developed land use, and low per capita developed land use tended to have high concentrations of water pollutants. The impact of urban sprawl also shows clear spatial difference between suburban areas and central cities: The central cities experienced lower increases over time in specific conductance concentration, compared to suburban and rural areas. The impact of urban sprawl on water quality is attributed to the combined effects of population and land-use change. Per capita developed land use is a very important indicator for studying the impact of urban sprawl and improving land use and watershed management, because inclusion of this indicator can better explain the temporal and spatial variations of more water quality parameters than using individual land use or/and population density.     

Testing the environmental Kuznets curve hypothesis for water footprint indicator: a cross-sectional study

The water footprint analysis has become a rapidly growing field of research although little attention has been paid to its relationship with economic growth. Using the available cross-section data, this study examines how the per capita water footprint varies as a function of per capita income within the environmental Kuznets curve framework at both aggregated and disaggregated level of water footprint. In addition, the issue of omitted variables is investigated by incorporating a number of control variables. Estimation results show no evidence in favour of an inverted-U environmental Kuznets curve, but they yield, in most cases, an evolution into an N-shaped relationship. This means that water footprint rises in the beginning with incomes, then falls as nations grow wealthier to rise again at very high income levels. This calls into question the traditional economic view of income growth sustainability as it applies to water.     

Environmental space and barriers to local sustainability: Evidence from Edinburgh, Scotland

This paper steps into the minefield that is urban sustainability studies. It defends a rigorous definition of sustainable development called Environmental Space. This approach starts from the assumption that (1) there are limits to the biophysical capacity of the ecosystem and (2) that — within these limits — each individual has equal access rights to natural capital. On this basis, per capita sustainable consumption targets are calculated which can be (and are being) used as policy objectives. The paper explores how environmental space has influenced local sustainability politics in Edinburgh, Scotland. By doing so, it finds that environmental space targets are still far from being achieved. Reasons for this failure are investigated and Edinburgh's continued commitment to the material growth of her economy is identified as one key barrier. This point is illustrated through the investigation of recent policy decisions in Edinburgh which were justified as being necessary for growth, but which clearly contradict the aims of sustainable development.     

THE W-INDEX FOR RESIDENTIAL WATER CONSERVATION1

ABSTRACT: An index of residential water efficiency - a “W-Index” - can serve as a measure of effectiveness of water conservation features in the home. The index provides a calculated numerical value for each dwelling unit, derived from the number and kind of water-saving features present, including indoor and outdoor water savers and water harvesting or recycling systems. A W-Index worksheet, devised for on-site evaluation of single-family residences in the Tucson, Arizona, region shows that a nonconserving residence with all the water-using features would use 151,000 gallons per year or 148 gallons per capita per day (gpcpd), while the fully conserving model would use 35,300 gallons per year or 35 gpcpd and with water harvesting and graywater recycling systems would have a maximum W-Index of W-160. A Tucson water conservation demonstration home, Casa del Agua, received a rating of W-139, and field tests of about 30 homes in new Tucson subdivisions show values ranging from W-75 to W-100, indicating the incorporation of some water conservation in current new models. By adjustment of some climatic or water-use parameters, the W-Index format can be applied to various types of dwelling units or to other urban areas. The W-Index can be used by individual homeowners or builders to evaluate water efficiency of residential units, or by water providers or water management agencies as a device for promoting and achieving water conservation goals.     

COST BEHAVIOR AND WATER SYSTEMS1

ABSTRACT: Several factors theoretically affect the cost behavior of water systems. These factors include scale, consumer density, and per capita usage. This analysis examines the several possible influences on the unit costs of water service. The statistical analyses indicate that among the factors of scale, per capita use, and consumer density, only the first two factors are important influences on water system costs. Water consumers appear to benefit from being served by large systems and being located in service areas characterized by relatively high per capita consumption. There is little statistical evidence indicating that more dense areas can be provided water service at lower costs than less dense areas.     

A MUNICIPAL WATER SUPPLY INVESTMENT PROBLEM IN RHODE ISLAND1

ABSTRACT: The traditional “requirements” approach to water system planning presumes perfectly inelastic demand and arbitrarily selects a fixed water requirement per capita per day as a planning target. Economists have often pointed out that such a policy leads to over-investment in water supply facilities; a superior approach would maximize some measure of net benefits incorporating price-sensitive demand. Using a dynamic programming model to depict an investment problem in Rhode Island, we find that ambiguities about how to incorporate price-sensitive demand into a decision framework may make such an approach as arbitrary as the requirements approach. Water conservation responses may be a function of other social parameters than water price; if so, variations in these social parameters should be regarded as economic alternatives to water supply investments.     

湖南城乡居民虚拟水消费结构及其用水效率评价

运用水足迹方法,根据2000—2008年的统计资料,对湖南省城乡居民虚拟水消费结构和城乡居民用水效率进行综合评价。结果表明,近年来湖南省总水足迹和人均水足迹均呈下降趋势;城镇居民虚拟水消费结构多样性指数值高于农村,城镇居民消费观念和消费模式更为合理;虚拟水消费结构多样性指数整体呈上升趋势,居民消费结构逐渐转向多元化;社会水资源稀缺指数不高,水资源利用还有较大空间,利用效率有了明显提高。     

Travelling Distances,Modal Split and Transportation Energy in Thirty Residential Areas in Oslo

A study of the use of car and public transport among residents in 30 residential areas in Greater Oslo indicates that urban planning variables have a significant influence on the energy use per capita for local transport. Residents in local communities with a high density and a short distance to downtown Oslo travel considerably shorter distances and use considerably less energy per capita than those who live in low-density, outer areas. This is true also when the effects of other variables are neutralized. The influence of urban planning variables on the modal split is lower than on energy use. The distribution between public and private transport is influenced most of all by car ownership.     

Water conservation due to greywater treatment and reuse in urban setting with specific context to developing countries

In India, the per capita water availability is reducing day by day due to rapid growth in population and increasing water demand. Greywater treatment and reuse is one of the feasible options in developing countries like India to overcome this problem. A greywater collection, treatment and reuse system was designed and implemented in an urban household having a water requirement of 165 liter per capita per day (lpcd) and a greywater generation rate of 80 lpcd. An upflow-downflow greywater treatment plant having a screening, sedimentation, filtration and disinfection as major treatment processes was constructed and treated greywater is used for toilet flushing and to irrigate the vegetables in the backyard of the household. Greywater characterisation indicates that COD and BOD are sufficiently reduced during the treatment and there is also substantially reduction in Escherichia coli count. The payback period of this greywater treatment and reuse system is estimated to be 1.6 year.     

PROJECTED INCREASES IN MUNICIPAL WATER USE IN THE GREAT LAKES DUE TO CO2-INDUCED CLIMATIC CHANGE1

ABSTRACT: Two scenarios of CO₂-induced climatic change are used to estimate changes in water use for a number of municipalities in the Great Lakes region of Canada and the United States. Both scenarios, based on General Circulation Models produced by the Goddard Institute for Space Studies (GISS) and Geophysical Fluid Dynamics Lab (GFDL), project warmer temperatures for the region. Using regression models based on monthly potential evapotranspiration for individual cities, it is projected that annual per capita water use will increase by a small amount, which will probably have only a marginal effect on water supplies in the Great Lakes basin. This method could also be used to assess the potential impacts of CO₂-induced climatic change on water use by the agriculture and power sectors, as well as the effectiveness of water policy initiatives, such as price changes. More work is needed to project water use during peak periods (warm dry spells), which may occur more frequently in a 2 × CO₂ climate in this region.     

System dynamics modeling for municipal water demand estimation in an urban region under uncertain economic impacts

Accurate prediction of municipal water demand is critically important to water utilities in fast-growing urban regions for drinking water system planning, design, and water utility asset management. Achieving the desired prediction accuracy is challenging, however, because the forecasting model must simultaneously consider a variety of factors associated with climate changes, economic development, population growth and migration, and even consumer behavioral patterns. Traditional forecasting models such as multivariate regression and time series analysis, as well as advanced modeling techniques (e.g., expert systems and artificial neural networks), are often applied for either short- or long-term water demand projections, yet few can adequately manage the dynamics of a water supply system because of the limitations in modeling structures. Potential challenges also arise from a lack of long and continuous historical records of water demand and its dependent variables. The objectives of this study were to (1) thoroughly review water demand forecasting models over the past five decades, and (2) propose a new system dynamics model to reflect the intrinsic relationship between water demand and macroeconomic environment using out-of-sample estimation for long-term municipal water demand forecasts in a fast-growing urban region. This system dynamics model is based on a coupled modeling structure that takes into account the interactions among economic and social dimensions, offering a realistic platform for practical use. Practical implementation of this water demand forecasting tool was assessed by using a case study under the most recent alternate fluctuations of economic boom and downturn environments.     

秦皇岛市城镇水土保持工作主要做法及成效分析

随着城镇建设的迅猛发展,项目开发建设占用大量具有生态功能的地表,人为造成的水土流失日趋严重,因此做好城镇水土保持工作至关重要。秦皇岛市从2004年起通过制定规划、建立工作体系、强化预防监督、加强宣传等措施,水土保持工作取得了显著成效:提高了全民水保法制观念,规范了城镇建设项目管理工作,城郊水土流失治理度达90%以上,城区碧水工程已基本完成,实施了城市雨水资源利用试点工程,城市区人均绿地面积达到12 m2,森林覆盖率达40%以上。     

烟台市水环境污染与经济发展的关系研究

对烟台市2001~2017年水环境质量与经济发展的系列数据进行收集、整理及分析后,建立以环境库兹涅茨曲线(EKC)及其相关理论为基础的烟台市人均GDP与烟台市水环境污染指标的计量模型。对结果进行分析后发现:烟台市工业污水排放量对数值与人均GDP对数值间关系呈倒“N”形曲线,烟台市城乡居民生活污水排放量与人均GDP间关系大致呈倒“U”形曲线。烟台市的水环境问题在一段时间内有所缓解,但随着经济发展有出现新问题的可能,为了持续对污水排放进行防治,烟台市应继续采取因地制宜的水环境保护措施。     

COMPUTATIONAL IMPROVEMENT FOR STOCHASTIC DYNAMIC PROGRAMMING MODELS OF URBAN WATER SUPPLY RESERVOIRS1

ABSTRACT: This paper describes two methods that are introduced to improve the computational effort of stochastic dynamic programming (SDP) as applicable to the operation of multiple urban water supply reservoir systems. The stochastic nature of streamflow is incorporated explicitly by considering it in the form of a multivariate probability distribution. The computationally efficient Gaussian Legendre quadrature method is employed to compute the conditional probabilities of streamflow, which accounts for the serial correlation of streamflow into each storage and the cross correlation between the streamflow into various storages. A realistic assumption of cross correlation of streamflow is introduced to eliminate the need to consider the streamflow combinations which are unlikely to occur in the SDP formulation. A “corridor” approach is devised to eliminate the need to consider the infeasible and/or inferior storage volume combinations in the preceding stage in computing the objective function in the recursive relation. These methods are verified in terms of computational efficiency and accuracy by using a hypothetical example of three interconnected urban water supply reservoirs. Therefore, it can be concluded that these methods allow SDP to be more attractive for deriving optimal operating rules for multiple urban water supply reservoir systems.     

Are denser cities greener? Evidence from China, 2000–2010

Whether a city develops into a more compact one with a higher density or a more sprawling one may affect multiple aspects of the urban environment, including ecosystem health, greenhouse gas emissions, and quality of life. Using panel data gathered from China's cities from 2000 to 2010, we take advantage of the significant variation in the temporal change of density across cities to estimate the relationship between gross urban population density and multiple indicators of urban greenness. Fixed‐effects estimates support the widely held belief that density improves air quality and reduces the per capita carbon footprint. Results also suggest that higher density reduces the growth of road infrastructure and vehicle ownership and promotes walking. While density often translates into proximity and accessibility, higher density does reduce a city's per capita urban park and green space. This study strengthens the urban policy and planning literature with much needed longitudinal evidence. Our overall findings support higher density as opposed to lower density urban development in China.     

Probabilistic Flood Inundation Forecasting Using Rating Curve Libraries

One approach for performing uncertainty assessment in flood inundation modeling is to use an ensemble of models with different conceptualizations, parameters, and initial and boundary conditions that capture the factors contributing to uncertainty. However, the high computational expense of many hydraulic models renders their use impractical for ensemble forecasting. To address this challenge, we developed a rating curve library method for flood inundation forecasting. This method involves pre‐running a hydraulic model using multiple inflows and extracting rating curves, which prescribe a relation between streamflow and stage at various cross sections along a river reach. For a given streamflow, flood stage at each cross section is interpolated from the pre‐computed rating curve library to delineate flood inundation depths and extents at a lower computational cost. In this article, we describe the workflow for our rating curve library method and the Rating Curve based Automatic Flood Forecasting (RCAFF) software that automates this workflow. We also investigate the feasibility of using this method to transform ensemble streamflow forecasts into local, probabilistic flood inundation delineations for the Onion and Shoal Creeks in Austin, Texas. While our results show water surface elevations from RCAFF are comparable to those from the hydraulic models, the ensemble streamflow forecasts used as inputs to RCAFF are the largest source of uncertainty in predicting observed floods.     

MISCELLANEOUS PUBLICATIONS AND FILMS

Ten years ago in the United States, per capita water use for all purposes was about 1500 gallons a day. By the year 2000, our population will have grown from 200 to 350 million, and each person, in effect, will be using 2500 gallons per day, This could result in our using as much as 75 percent of the total average runoff from US. Rivers
Perhaps as much as 40,000 cubic miles of saline water are stored in rocks at various depths underlying extensive areas of the United States, according to the U.S. Geological Survey. This water, once considered of no value and even a nuisance, now represents a vast potential source of water, either as replacement of fresh water for certain uses or as the raw material for desalting techniques which have been studied intensively in recent years. Desalination creates new water in the sense that saline water, never before used, becomes part of our water economy.