Conventional and holistic urban stormwater management in coastal cities: a case study of the practice in Hong Kong and Singapore

This study compares stormwater management in two coastal cities: Hong Kong and Singapore. Hong Kong adopted conventional urban stormwater management for flood control and embraced hard-engineering infrastructure in the scheme. In contrast, Singapore has put in place a series of holistic management practices to manage urban runoff. By comparing the stormwater management practices in these two cities, the differences in approaches to non-structural and structural practices were elucidated. Life cycle costing and environmental benefit analysis indicate that holistic urban stormwater management can lead to higher economic efficiency, sustainability and environmental friendliness, compared to conventional urban stormwater management.     

Analysis and Modelling of Stormwater Volume Control Performance of Rainwater Harvesting Systems in Four Climatic Zones of China

Rainwater harvesting has been widely used to alleviate urban water scarcity and waterlogging problems. In this study, a water balance model is developed to continuously simulate the long-term (57 to 65 years) stormwater capture efficiency of rainwater harvesting systems for three water demand scenarios at four cities across four climatic zones of China. The impacts of the “yield after spillage” (YAS) and “yield before spillage” (YBS) operating algorithms, climatic conditions, and storage and demand fractions on stormwater capture efficiency of rainwater harvesting systems are analyzed. The YAS algorithm, compared with the YBS, results in more conservative estimations of stormwater capture efficiency of rainwater harvesting systems with relatively small storage tanks (e.g., ≤50 m³). The difference between stormwater capture efficiency calculated using the YBS and YAS algorithms can be remedied by increasing storage capacity and reduced by decreasing water demand rates. Higher stormwater capture efficiency can be achieved for rainwater harvesting systems with higher storage and demand fractions and located in regions with less rainfall. However, the lager variations in annual rainfall in arid zones may lead to unstable stormwater management performance of rainwater harvesting systems. The impacts of storage and demand fractions on stormwater capture efficiency of rainwater harvesting systems are interactive and dependent on climatic conditions. Based on the relationships among storage capacity, contributing area, water demand, and stormwater capture efficiency of rainwater harvesting systems, easy-to-use equations are proposed for the hydrologic design of rainwater harvesting systems to meet specific stormwater control requirements at the four cities.     

美国城市雨洪管理水文控制指标体系及其借鉴意义

我国在海绵城市建设试点阶段,亟待探讨如何构建适宜的水文控制指标体系。在近半个世纪的城市雨洪管理实践中,美国整合出一套水文控制指标体系,包括维持河湖湿地基流与地下水补给的入渗控制指标,减少雨洪面源污染的水质控制指标,防止河道侵蚀的水土侵蚀控制指标,以及避免小量级洪涝和减轻极端洪涝灾害的洪水控制指标。在调研美国城市雨洪管理沿革的基础上,对我国目前开展的海绵城市试点工作中的径流控制指标进行了对比研究;包括指标确定方法比较,指标划分与实施比较,以及指标的涵盖范围与效益分析。在此基础上,提出了我国海绵城市试点建设中确定水文控制指标所亟待开展的工作,包括基础科研领先,数据与成果共享,加强区域及部门间合作以及推行多指标水文控制体系的理念与实践。本文为海绵城市建设中合理确定适合各地具体条件的水文控制指标体系提供研究思路与参考。     

Utilising integrated urban water management to assess the viability of decentralised water solutions

Cities worldwide are challenged by a number of urban water issues associated with climate change, population growth and the associated water scarcity, wastewater flows and stormwater run-off. To address these problems decentralised solutions are increasingly being considered by water authorities, and integrated urban water management (IUWM) has emerged as a potential solution to most of these urban water challenges, and as the key to providing solutions incorporating decentralised concepts at a city wide scale. To incorporate decentralised options, there is a need to understand their performance and their impact on a city's total water cycle under alternative water and land management options. This includes changes to flow, nutrient and sediment regimes, energy use, greenhouse gas emissions, and the impacts on rivers, aquifers and estuaries. Application of the IUWM approach to large cities demands revisiting the fundamental role of water system design in sustainable city development. This paper uses the extended urban metabolism model (EUMM) to expand a logical definition for the aims of IUWM, and discusses the role of decentralised systems in IUWM and how IUWM principles can be incorporated into urban water planning.     

Commentary

This paper presents an urban water management framework consisting of six requisites for effective water management identified based on a literature review: source water protection; stormwater management; water conservation; water pricing; wetland conservation; and drought management. The objective was to test the requisite framework in three Canadian urban centres within a region of increasing water stress, the Canadian Prairie. The findings point to variable water management efficiency across the study region and to requisite selection being regionally dependent. A common set of requisites may not be suitable for all urban regions when attempting to assess effective urban water management.     

Hydrological analysis of single and dual storage systems for stormwater harvesting

As stormwater flows are intermittent, the requirement to store urban runoff is important to the design of a stormwater re-use scheme. In many urban areas, the space available to provide storage is limited and thus the need to optimise the storage volume becomes critical. This paper will highlight the advantages and disadvantages of two different approaches of providing storage: 1) a single shallow storage (0.5 m depth) in which stormwater capture and a balanced release to supply users is provided by the one unit; and 2) a dual system in which the functions of stormwater capture and supply release are provided by two separate deeper storage units (2 m depth). The comparison between the two strategies is supported by water balance modelling assessing the supply reliability and storage volume requirements for both options. Above a critical volumetric capacity, the supply yield of a dual storage system is higher than that from a single storage of equal volume mainly because of a smaller assumed footprint. The single storage exhibited greater evaporation loss and is more susceptible to algae blooms due to long water residence times. Results of the comparison provide guidance to the design of more efficient storages associated with stormwater harvesting systems.     

Impediments and constraints in the uptake of water sensitive urban design measures in greenfield and infill developments

Water sensitive urban developments are designed with integrated urban water management concepts and water sensitive urban design measures. The initiatives that may be included are the substitution of imported drinking water with alternative sources using a fit-for-purpose approach and structural and non-structural measures for the source control of stormwater. A water sensitive approach to urban development can help in achieving sustainability objectives by minimising disturbance to ecological and hydrological processes, and also relieve stress on conventional water systems. Water sensitive urban developments remain novel in comparison with conventional approaches, so the understanding and knowledge of the systems in regards to their planning; design; implementation; operation and maintenance; health impacts and environmental impacts is still developing and thus the mainstream uptake of these approaches faces many challenges. A study has been conducted to understand these challenges through a detailed literature review, investigating a large number of local greenfield and infill developments, and conducting extensive consultation with water professionals. This research has identified the social, economic, political, institutional and technological challenges faced in implementing water sensitive urban design in greenfield and infill developments. The research found in particular that there is the need for long-term monitoring studies of water sensitive urban developments. This monitoring is important to validate the performance of novel approaches implemented and improve associated guidelines, standards, and regulatory and governance frameworks, which can lead to mainstream acceptance of water sensitive urban development approaches. The dissemination of this research will help generate awareness among water professionals, water utilities, developers, planners and regulators of the research challenges to be addressed in order to achieve more mainstream acceptance of water sensitive approaches to urban development. This study is based on existing water sensitive urban developments in Australia, however, the methodology adopted in investigating impediments to the uptake of these developments can be applied globally. It is hoped that insights from this study will benefit water professionals in other countries where there is also a move towards water sensitive urban development.     

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.     

"Triple-bottom-line" assessment of urban stormwater projects.

New guidelines have been developed and trialled in Australia to assist urban stormwater managers to assess options for projects that aim to improve urban waterway health. These guidelines help users to examine the financial, ecological and social dimensions of projects (i.e., the so-called "triple-bottom-line"). Features of the assessment process described in the guidelines include use of multi criteria analysis, input from technical experts as well as non-technical stakeholders, and provision of three alternative levels of assessment to suit stormwater managers with differing needs and resources. This paper firstly provides a background to the new guidelines and triple-bottom-line assessment. The assessment methodology promoted in the new guidelines is then briefly summarised. This methodology is compared and contrasted with European guidelines from the "SWARD" project that have been primarily developed for assessing the relative sustainability of options involving urban water supply and sewerage assets. Finally, the paper discusses how assessment methodologies that evaluate the financial, ecological and social dimensions of projects can, under some circumstances, be used to evaluate the relative progress of options for urban water management on a journey towards the widely pursued, but vaguely defined goal of "sustainable development".     

Achieving multiple benefits from stormwater harvesting.

As the concept of integrated urban water management is incorporated into the practice of urban water servicing, new options, such as stormwater harvesting, which can have multiple benefits, are of increasing interest. The multi-functional benefits of stormwater harvesting include the potential to enhance urban stream health through improvements to the flow regime as well as providing a valuable water supply source. This paper synthesises a current research programme being undertaken to assess the viability of, and develop recommendations for, stormwater harvesting. The design of the collection, treatment, storage, flood protection, and distribution components of an integrated system are each discussed, along with the environmental flow consequences of urban stormwater harvesting. The incorporation of swales and biofilters into the collection system was not found to lead to significant exfiltration and evaporation losses in most circumstances and so can be employed as part of the treatment train. Further treatment can be provided by WSUD-type biophysical measures such as ponds, wetlands or novelly designed biofilters or physio-chemical treatment processes. Depending on the design, the stormwater storage component may or may not provide flood protection. In many circumstances, the storage capacity requirements are not considered to be a barrier to stormwater harvesting.     

Integrated solutions for urban runoff pollution control in Brazilian metropolitan regions

One of the most important causes for poor water quality in urban rivers in Brazil is the low collection efficiency of the sewer system due to unforeseen interconnections with the stormwater drainage system. Since the beginning of the 20th century, Brazilian cities have adopted separate systems for sanitary sewers and stormwater runoff. Gradually these two systems became interconnected. A major challenge faced today by water managers in Brazil is to find efficient and low cost solutions to deal with this mixed system. The current situation poses an important threat to the improvement of the water quality in urban rivers and lakes. This article presents an evaluation of the water quality parameters and the diffuse pollution loads during rain events in the Pinheiros River, a tributary of the Tietê River in S?o Paulo. It also presents different types of integrated solutions for reducing the pollution impact of combined systems, based on the European experience in urban water management. An evaluation of their performance and a comparison with the separate system used in most Brazilian cities is also presented. The study is based on an extensive water quality monitoring program that was developed for a special investigation in the Pinheiros River and lasted 2.5 years. Samples were collected on a daily basis and water quality variables were analyzed on a daily, weekly or monthly basis. Two hundred water quality variables were monitored at 53 sampling points. During rain events, additional monitoring was carried out using an automated sampler. Pinheiros River is one of the most important rivers in the S?o Paulo Metropolitan Region and it is also a heavily polluted one.     

城市绿色道路及雨洪控制利用策略研究

城市雨洪控制利用措施与城市发展及基础设施建设的不协调,导致城市化过程中水环境退化,产生严重的水涝、径流污染、地下水位下降等城市水环境和生态问题.道路作为城市的主要下垫面和重要的排水通道,雨水问题十分突出.针对我国传统道路排水的主要问题,总结国内外道路雨洪控制利用新思路——基于LID/GSI的绿色道路,结合我国研究现状,提出我国城市道路雨洪控制利用策略,并以杭州余杭塘立交为例,分析道路雨洪控制利用措施的应用.     

Offline Optimization of Sluice Control Rules in the Urban Water System for Flooding Mitigation

A real-time control (RTC) system can substantially improve the efficiency in urban flooding mitigation by optimizing the capacity of drainage and storage in existing drainage systems. However, few studies have investigated the RTC for an Urban Water System (UWS) in cities with a high water surface ratio for flooding mitigation. In this study, control rules of the actuators in an UWS were developed by an offline optimization system that combines a hydraulic model, the stormwater management model (SWMM) with an optimization model solved by the differential evolution (DE) algorithm. Iteratively simulating only the downstream UWS hydraulic model, the objectives of this study were to (i) minimize the flooding volume from the UWS and (ii) minimize the cumulative water depths above the control lines in real-time. Results showed that the optimal control rules outperformed the current fully open and closed rules, indicating the UWS’s retaining and draining capacity was effectively utilized through the offline optimization. This study also found that the robust control rules might be biased and have little effect under most rainfalls, especially mild storms, as they are derived from the system’s average performance under various rainfall conditions.

     

Stormwater reuse: designing biofiltration systems for reliable treatment.

Stormwater reuse is increasing in popularity as a technique for overcoming water shortages in urban Australia. However, technology for the reliable treatment of stormwater for reuse is still not fully developed. This paper presents the first steps in refining biofilters for stormwater reuse. Six different filter media were selected, to target specific stormwater pollutants, as well as support plant growth. They were tested in the laboratory, where the filters were dosed three times per week with semi-synthetic stormwater for five weeks. Pollutant removal performance was monitored, and revealed that all soil-based filters performed similarly (while sand filters behaved somewhat differently). All filters removed more than 80% of solids and greater than 90% of lead, copper, and zinc. Three filter types were able to remove some phosphorus (particularly in the top 30 cm of the media). Apart from sand, all filter media were net producers of nitrogen, leading to an important conclusion that non-vegetated, soil-based filters are not suitable for targeting nutrients. However, since heavy metals are the primary pollutant of concern with respect to stormwater reuse for irrigation (the most popular end-use), it was concluded that biofilters may be promising technologies for treatment of stormwater for reuse.     

城市水管理与海绵城市建设之理论基础—城市水文学研究进展

过去数十年来,我国经济社会快速发展,城市化进程不断加快,但由于不合理的城市规划和建设,自然水循环系统受到无序的干扰和破坏,引发了一系列城市水问题,城市水管理工作面临巨大挑战。城市水管理的理论支撑就是以研究城市水循环为核心的城市水文科学,"海绵城市"建设作为我国现代城市水管理的重大战略,必须以城市水文学理论为依据,深入研究城市水循环机理和规律。本文围绕城市水管理支撑理论,系统梳理了国内外在城市化水文效应、城市产汇流理论、城市雨洪模拟与管理方面的研究进展,指出城市水文观测与预报、城市化水文效应与产汇流理论、城市综合水系统模型研究是当前和未来一段时间研究的重点和难点。提出了我国当前城市水管理和海绵城市建设所面临的城市产汇流基础理论、城市气象水文监测和水文过程模拟技术问题,以及城市水文学研究应对变化环境下城市复杂的综合水问题开展基于多学科理论的全面精细化模拟分析的基本思路。     

城市历史水系修复规划思路与策略研究——以长春市为例

随着近年来城市水系治理和旧城更新、历史文化复兴的开展,城市历史水系的修复越来越受到各界的关注,如何使历史水系修复与规划设计体系相结合已然成为重要议题。借助于文献综述、历史地图分析、案例的实际应用等方法展开研究,并提出了城市历史水系修复的规划目标、指标和实施途径,以及水系修复项目的工作流程。在此基础上,以长春市老城区为例,对"一纵五横"历史水系的演变过程和现状进行了调研与评估,通过基于水系留存率、内涝黑臭、遗产保留状况等方面情况来确定水系的修复工程时序,提出了治理内涝黑臭、强化水系格局、盘活滨水空间及加强公众参与的修复策略。论文研究成果可为中国其他地区及历史文化名城的水系修复提供一定的参考。     

城市暴雨雨水水质管理模型简介

对目前国外常用的一些城市暴雨雨水水质管理模型作了较为全面的介绍和比较，阐述了各个模型的特点和适应性，有助于适当地选用这些模型，同时，对我国开展城市暴雨雨水管理系统的研究具有一定的借鉴作用     

Filter media for stormwater treatment and recycling: the influence of hydraulic properties of flow on pollutant removal.

Improved urban water management in Australia is of national importance. Water resources are stretched and urban runoff is a recognized leading cause of degradation of urban waterways. Stormwater recycling is an option that can contribute to easing these problems. Biofilters are effective structural stormwater pollution control measures with the potential for integration into stormwater treatment and recycling systems. However, premature clogging of biofilters is a major problem, with resulting decreased infiltration capacity (and hence the volume of stormwater the system can detain) and increased detention time. This paper presents preliminary findings with respect to the effect of clogging on pollutant removal efficiency in conventional stormwater filter media. A one-dimensional laboratory rig was used to investigate the impact of clogging on pollutant removal efficiency in a conventional biofiltration filter media (gravel over sand). Both the individual gravel layer and the overall multi-filter were highly efficient at removing suspended solids and particulate-associated pollutants. This removal efficiency was consistent, even as the filters became clogged. Removal of dissolved nutrients was more variable, with little reduction in concentrations overall. Although preliminary, these results challenge the concept that increased detention time improves the treatment performance of stormwater filtration systems.     

中国海绵城市开发与加拿大综合雨洪管理对比研究:以多伦多为例

介绍了加拿大城市流域雨洪规划管理的发展进程以及加拿大最大城市——多伦多市雨洪管理的政策、原则和标准,与中国的海绵城市建设技术指南进行对比,对指南中存在的一些问题,如指南未给出LID设计的检验和校核方案,也未充分考虑降雨等问题进行讨论,旨在为中国的雨洪管理提供新的研究思路和参考。