Showing papers in "Urban Water Journal in 2017"

Recognising barriers to implementation of Blue-Green Infrastructure: a Newcastle case study

Abstract: There is a recognised need for a fundamental change in how the UK manages urban water and flood risk in response to increasingly frequent rainfall events coupled with planned urban expansion. Approaches centred on ‘living with and making space for water’ are increasingly adopted internationally. Nonetheless, widespread implementation of Blue-Green infrastructure (BGI) is currently hampered by barriers that impede uptake and innovation. We investigate the barriers to implementation of BGI in Newcastle, UK, through a series of semi-structured interviews with professional stakeholders. We identify and categorise 17 types of barrier and identify targeted strategies to overcome the dominant barriers. We recommend promotion of BGI’s capacity to meet the objectives of multiple organisations and Local Authority departments, in addition to managing urban water. We conclude that strong business cases, supported by monetised evidence of benefits, and collaborative, inter-agency working could advance implementation of BGI within the current flood risk management legislation.

A review of data-driven approaches for burst detection in water distribution systems

Abstract: This study focuses on data-driven approaches for burst detection and classifies them into three categories: classification method, prediction-classification method and statistical method. The performance of these methods is discussed. By analysing uncertainty in burst detection, this paper revealed that non-stationary monitoring data and limitations present in these methods challenge the reliability of detection results. Data pre-processing and probabilistic solutions to deal with the uncertainty are summarised. From these findings and discussions, this paper concludes and recommends that: a) data-driven approaches are promising in real-life burst detection and reducing false alarms is an important issue; b) more comprehensive performance evaluation might be necessary, in particular regarding detectable burst size; c) further research on new methods employing multivariate analysis and a new category based on clustering analysis would be beneficial to tackle uncertainty; d) more focus on the use of...

Stormwater control measure (SCM) maintenance considerations to ensure designed functionality

Abstract: Great investment is made in the design and installation of stormwater control measures (SCMs). Substantial research investment, too, is made to optimise the performance of SCMs. However, once installed, SCMs often suffer from lack of maintenance or even outright neglect. Key maintenance needs for wet ponds, constructed stormwater wetlands, bioretention, infiltration practices, permeable pavement, swales, and rainwater harvesting systems are reviewed with many tasks, such as the cleaning of pre-treatment areas and the preservation of infiltration surfaces, being common maintenance themes among SCMs. Consequences of lacking maintenance are illustrated (mainly insufficient function or failure). Probable reasons for neglect include insufficient communication, unclear responsibilities, lack of knowledge, financial barriers, and decentralised measures. In future designs and research, maintenance (and lack thereof) should be considered. Assessing the performance of SCMs conservatively and including safet...

Water services performance: do operational environment and quality factors count?

Abstract: Decision makers must keep in mind that water services have an invaluable ‘price’ for the public budget and society’s welfare. However, due to the specific features of the service, water utilities are prone to inefficiency. Thus, performance evaluation becomes indispensable to face this constraint. Besides the application of the traditional technique of Data Envelopment Analysis to evaluate the performance of Portuguese water utilities, this study also implements the robust technique of order-m to assess the influence of operational environment on water utilities’ performance. In spite of several reforms, the Portuguese water sector still reveals significant levels of inefficiency, partially caused by an inappropriate operating scale. Concerning the operational environment, it was possible to observe a positive influence of private sector participation, economies of scope, and groundwater sources on efficiency. The influence of the ‘quality of service provided’ was also studied in this performance ...

Defining green roof detention performance

Abstract: Although it is widely accepted that the detention performance of green roofs is of interest to stormwater engineers and planners, no single metric allows detention to be unambiguously defined. Detention effects are highly sensitive to rainfall characteristics and antecedent conditions, and individual roofs typically exhibit wide variations in detention performance between storm events. This paper uses a straightforward hydrological model to explore two alternative approaches to describing detention performance: a probabilistic approach based on long time-series simulations; and a design storm approach. It is argued that the non-linear reservoir routing parameters (scale, k and exponent, n) provide fundamental descriptors of the detention process, with modelling enabling performance to be determined for specific rainfall inputs. The study utilises 30-year rainfall time-series predictions for four contrasting UK locations to demonstrate the utility of the two proposed design approaches and to comment on loc...

State-of-the-art review of water pipe failure prediction models and applicability to large-diameter mains

Abstract: This paper provides an overview of the work performed in the last 13 years to predict the failure of large-diameter trunk water mains. Large-diameter water mains, defined as water mains with a diameter greater than 500 mm, form the main transmission lines in most water distribution systems. The consequences of their failure can be severe and costly. In order for predictive models to be applicable to large-diameter water mains, all models reviewed are capable of analysing individual pipes or pipe segments and calculate either an absolute probability of failure or the hazard of failure relative to other pipes in the system. These models can be divided into two broad categories: physical and statistical models. This review provides a description and a brief critique for each model presented.

A new experiments-based methodology to define the stability threshold for any vehicle exposed to flooding

Abstract: A vehicle exposed to flooding, after losing stability, becomes buoyant and may be washed away with potential injuries and fatalities. Such vehicles cause additional disruption to traffic that is already affected by flooding, which may lead to substantial indirect economic impact, especially in urban areas. Therefore, the analysis of the stability of vehicles exposed to flooding is important in order to make decisions to reduce damages and hazards. In this research, based on an experimental campaign that included a range of twelve car models, a new methodology to obtain the stability threshold for any real vehicle exposed to flooding is developed. A stability coefficient (SCmod) is derived with which the vehicles can be sorted by stability against water flows and their stability functions may be determined. The experiments were conducted with three different model scales (1:14, 1:18 and 1:24) and involved analysis of both friction and buoyancy effects, which made this the most comprehensive researc...

Using extreme learning machines for short-term urban water demand forecasting

Abstract: This study explores the ability of various machine learning methods to improve the accuracy of urban water demand forecasting for the city of Montreal (Canada). Artificial Neural Network (ANN), Support Vector Regression (SVR) and Extreme Learning Machine (ELM) models, in addition to a traditional model (Multiple linear regression, MLR) were developed to forecast urban water demand at lead times of 1 and 3 days. The use of models based on ELM in water demand forecasting has not previously been explored in much detail. Models were based on different combinations of the main input variables (e.g., daily maximum temperature, daily total precipitation and daily water demand), for which data were available for Montreal, Canada between 1999 and 2010. Based on the squared coefficient of determination, the root mean square error and an examination of the residuals, ELM models provided greater accuracy than MLR, ANN or SVR models in forecasting Montreal urban water demand for 1 day and 3 days ahead, and can...

Validation of a 1D-2D dual drainage model under unsteady part-full and surcharged sewer conditions

Abstract: This paper presents a 1D-2D dual drainage model to compute the rainfall-runoff transformation in urban environments. Overland flow in major drainage systems is modelled with the 2D shallow water equations, whereas the flow in a sewer network is computed with the 1D Saint-Venant equations using the two-component pressure approach to model pressure-flow conditions. The surface and sewer network models are linked through manholes, which allow water interchange in both directions. A new series of rainfall–runoff experiments in a real-scale physical model of a street section is used to validate the model under unsteady part-full and pressure flow conditions. The experimental measurements of water depth and discharge at several locations in a drainage network show a very satisfactory performance of the numerical model.

Amsterdam as a sustainable European metropolis: integration of water, energy and material flows

Abstract: ABTRACTAmsterdam has the ambition to develop as a competitive and sustainable European metropolis. The flows of energy, water and resources within the urban environment have a large potential to contribute to this ambition. Through a transition from a linear usage of resources and waste production towards a sustainable management of urban resources with circular flows of resources, the sustainability of cities can be increased. This Urban Harvesting Concept may be applied in Amsterdam. The challenge is how to operationalize this concept in practice. For two municipal companies in Amsterdam, Waternet (responsible for the water management) and AEB (the waste-to-energy company), initiatives were identified on how to do this. The focus is on water, energy, waste and material flows. Circular flows result in economic benefits and sustainability benefits, either expressed as Ecopoints or CO2-emissions. The integration of these flows is especially beneficial.

Standing on the shoulders of giants: Understanding changes in urban water practice through the lens of complexity science

Abstract: Scholars assert that traditional approaches to urban water management need reforming. These debates have identified the need to move toward systems and complexity thinking. The literature offers limited insight into the utility of complexity theory in enhancing urban water policy and practice. This paper aims to address this gap by: (i) synthesizing the intellectual history of complexity science, (ii) identifying key principles of complexity theory and (iii) providing insights into how complexity theory can contribute to twenty-first century urban water management. We reveal how Newtonian logic is deeply embedded in contemporary Western urban water policy and practice. We identify three insights from complexity science that could potentially yield better urban water policy and practice outcomes: system boundaries; agents and networks; and far from equilibrium. These theoretical insights offer an important contribution to scholarly debates as embedded normative frameworks need to be recognized, und...

Conventional and decentralized urban stormwater management: A comparison through case studies of Singapore and Berlin, Germany

Abstract: Urban stormwater runoff is both a significant pollution source and a potentially valuable resource. This study compares stormwater management in two cities: Singapore and Berlin, Germany. In comparing the strategies for stormwater management, we illustrate how differences in geography (e.g., land and water availability), urban infrastructure, regulatory regimes, legislation and intensives between the two cities have led to different solutions for stormwater management. Singapore, faced with a serious issue of water scarcity, has placed an increasing emphasis on stormwater management through developing a comprehensive network of drains and canals, mainly with the aim of controlling flooding and potable water supply. In contrast, in Berlin, concerns for the protection of surface water quality and non-potable water supply in the urban areas have resulted in a shift in management goals towards a low impact solution based on source control. The cost analysis indicated that the decentralized rainwater h...

Development and application of an automated subcatchment generator for SWMM using open data

Abstract: An open source subcatchment generator program was developed for the Stormwater Management Model (SWMM) to automate tedious stages in the model construction process. The generator divides the invest...

Assessing methods for predicting green roof rainfall capture: A comparison between full-scale observations and four hydrologic models

Abstract: To optimize the application of green roof technology, there is a need to quantify stormwater mitigation in advance of green roof construction. This study contributes toward meeting this need by assessing the utility of four hydrologic models for predicting green roof rainfall capture, including the: (1) curve number method, (2) characteristic runoff equation, (3) Hydrological Evaluation of Landfill Performance (HELP V3.9D) model, and (4) Storm Water Management Model (SWMM V5.1). Modeling results were compared to over twenty-four months of observed runoff data, collected between June 2011 and December 2013, from two full-scale green roofs in New York City (NYC). Both the curve number method and characteristic runoff equation had the highest Nash-Sutcliffe efficiency index (NSEI) between modeled and observed cumulative runoff depth per event (NSEI = 0.97) due to parameter calibration requirements, where error was mainly due to variations in green roof antecedent moisture conditions. The HELP model was origi...

Mesocosm study of enhanced bioretention media in treating nutrient rich stormwater for mixed development area

Abstract: A well-designed engineered soil for bioretention is important as it ensures that pollutant removal requirements are met. This laboratory study investigated the nutrient removal efficiency of bioretention media enhanced with 10% (by volume) additives from various waste materials (cockle shell, newspaper, printed paper, coconut husk and tyre crumb) and planted with Red Hot Chinese Hibiscus (Hibiscus rosa-sinensis), a common landscape shrub in tropical countries. The results showed that media enhanced with shredded newspaper demonstrated a significant improvement in total nitrogen (TN) removal (80.4%), compared to standard bioretention media (57.5%) without compromising total suspended solids (TSS) and total phosphorus (TP) removal, when dosed with actual runoff. The thick root system and rapid growth rate of the plant was proven to contribute to TN removal. This study concluded that shredded newspaper can be a potential addition to enhance bioretention media performance in treating stormwater, espec...

The hydrologic outcome of a Low Impact Development (LID) site including superposition with streamflow peaks

Abstract: Hydrology plays a key role in mitigating environmental impacts with Stormwater Management (SWM). Site-level Low Impact Development (LID) is a promising approach but impeded by a lack of experience, performance metrics and comprehensive analysis. This study investigated the hydrologic performance of a small LID site (0.15 km2) including superposition with high flows of the receiving stream by monitoring precipitation, discharge and streamflow for 30 months. The results (73% event capture, 66–87% volume reduction, 39 L/ha/s peak discharge, 4.5% streamflow amplification) implied that site-level LID provides an alternative to conventional SWM even for unfavourable conditions. Weak performance related to underground storage, antecedent conditions, storm characteristics and freezing periods occurred seasonally; and a minimum storm capture volume could not be observed, but a maximum retention capacity. Future LID site designs should consider these characteristics and limitations, together with a differen...

Pipeline failure prediction in water distribution networks using evolutionary polynomial regression combined with K-means clustering

Abstract: This paper presents a new approach for improving pipeline failure predictions by combining a data-driven statistical model, i.e. evolutionary polynomial regression (EPR), with K-means clustering. The EPR is used for prediction of pipe failures based on length, diameter and age of pipes as explanatory factors. Individual pipes are aggregated using their attributes of age, diameter and soil type to create homogenous groups of pipes. The created groups were divided into training and test datasets using the cross-validation technique for calibration and validation purposes respectively. The K-means clustering is employed to partition the training data into a number of clusters for individual EPR models. The proposed approach was demonstrated by application to the cast iron pipes of a water distribution network in the UK. Results show the proposed approach is able to significantly reduce the error of pipe failure predictions especially in the case of a large number of failures. The prediction models we...

The physical factors affecting heavy metals accumulated in the sediment deposited on road surfaces in dry weather: a review

Abstract: The main objective of this review is to identify and analyse physical factors (PF) involved in the heavy metal accumulation phenomenon in the road-deposited sediment (RDS) in dry weather. Electronic databases were used to establish an order of prevalence by establishing quartiles (Q-citation frequency) for the PF identified. The results show that the eleven PF can most likely be classified into three categories: climatic-anthropogenic-morphometric. The studies most frequently referenced land use (Q1), rainfall (Q2), particle size (Q2) and vehicles (Q3) as key PF. There is a similar behaviour between the concentrations of Zn-Pb-Cu associated with the RDS in dry weather and the dissolved fraction washed from the surface in road runoff. The size fraction <250 μm is representative of RDS to characterize the metals. The review expands knowledge about the influences of the PF in the processes of deposition-suspension-interception-removal of the metals load in road environments.

Evaluation of functional resilience in urban drainage and flood management systems using a global analysis approach

Abstract: Enhancing resilience in urban drainage systems (UDSs) requires new evaluation approaches that explicitly consider vital interactions between threats, system performance and resulting failure impacts during both normal and unexpected (exceptional) loading conditions. However, current reliability-based approaches only focus on prevention of functional (hydraulic) failures resulting from a specified design storm. In this study, the global resilience analysis (GRA) approach is further extended for evaluation of UDS performance when subject to a wide range of random functional failure scenarios (extreme rainfall) with varying magnitude, duration, and spatial distribution. The resulting loss of system functionality during the simulated failure scenarios is quantified using total flood volume and mean flood duration. System residual functionality for each considered rainfall block loading scenario is quantified using the functional resilience index. The developed approach has been successfully applied to...

Metabolism-modelling approaches to long-term sustainability assessment of urban water services

Abstract: There is a discernible need for a holistic, long-term and sustainability approach in decision-making in water and wastewater utilities around the world. Metabolism-based modelling, which can quantify various flows within an urban water system (UWS), has shown its effective usability for a more comprehensive understanding of the impacts of intervention strategies and can be used by any water utility for future planning of UWS. This study presents the main principles of a holistic Sustainability Assessment Framework which can be simulated by using two analytical, conceptual, mass-balance-based models to quantify relevant key performance indicators (KPIs) associated with the metabolic flows of the urban water cycle. These two models are WaterMet2 (WM2) and dynamic metabolism model (DMM), developed recently under the aegis of the EU TRUST (Transitions to the Urban Water Services of Tomorrow) project. There are clear differences between the two models which make them useful in different contexts and ci...

Experimental study on the hydrological performance of a permeable pavement

Abstract: Permeable pavements play an essential role in urban drainage systems, making them the subject of great interest to both researchers and practitioners. However, previous studies have demonstrated a significant degree of uncertainty regarding both the hydrological performance and the maintenance requirements of this type of pavement. Within this context, the presented research involved the construction of a one metre square surface area of permeable pavement and a laboratory rainfall simulator to investigate the influence of rainfall intensity on the hydrologic response of permeable pavements. The design of the permeable pavement complied with the SuDS Manual guidance and British Standards (BS 7533-13:2009). The laboratory test programme was designed to investigate the influence of rainfall intensity on the hydrologic response of permeable pavements. The results demonstrate that the hydrologic performance varied according to rainfall intensity. The total volume of discharge from the permeable paveme...

Innovative modeling framework for combined sewer overflows prediction

Abstract: Combined sewer overflows (CSOs) and street flooding are undesirable consequences of insufficient capacity of sewer networks and wastewater systems. These conditions degrade the water quality of the receiving waters, potentially damage infrastructure, and threaten public health. Significant efforts to prevent CSOs and alleviate flooding have been undertaken in Chicago, with the construction of the tunnel and reservoir plan (TARP). This study analyses the hydraulic response of the first tunnel built in Chicago “The Lawrence Avenue Tunnel” through a framework of hydrological and hydraulic models. This framework proved effective in CSO's volume, frequency and duration predictions as it yields simulation results of existing conditions that match well with available records. The findings also provide insights into the importance of system operation on CSOs occurrence and magnitude. Adaptive management of the tunnel during storm events is recommended to minimize the impact of CSOs.

Nutrient recovery and crop yield enhancement in irrigation with reclaimed wastewater: a case study

Abstract: The paper reports results of treated wastewater reuse field experiments carried out in Apulia (Southern Italy). Fennel and lettuce were irrigated with four different water sources: three reclaimed wastewater streams, obtained by applying different treatment schemes to the same municipal wastewater, and a conventional source (well water). Differences between the three effluents were significant in terms of suspended solids and faecal indicators. Both lettuce and fennel yields were enhanced by the high content of nutrients in the effluent of one of the treatment plants, which had been operated for partial nitrogen removal. In particular, fennel productivity was enhanced by replacing chemical fertirrigation with the supply of nutrients contained in the irrigation water.

A comprehensive and well tested energy balance for water supply systems

Abstract: This paper presents a novel energy balance scheme and performance indicators for assessing energy efficiency in water supply systems. This assessment consists of a three-step procedure: system characterisation and data collection, energy balance calculation and energy performance indicators assessment. The main innovation is the integrated approach between energy and water balances allowing the quantification of energy inefficiencies directly associated with water losses. Comprehensive energy performance indicators can be calculated by utilities with different maturity levels allowing a fair comparison of energy efficiency between systems with different layouts and operational schemes. This energy balance scheme has been applied by 17 water utilities in Portugal. Results have shown that systems provide more than twice the minimum energy necessary to supply their consumers and, consequently, there is a significant energy saving potential: 40% through water loss reduction, 30% for changes in network...

Coping strategies of households affected by flooding: A case study of Sekondi-Takoradi Metropolis in Ghana

Abstract: Annually, rivers close to communities within Sekondi-Takoradi Metropolis overflow their banks, especially during the rainy seasons; displacing thousands of residents. Despite this, little is known about the coping strategies used by the residents when flooding occurs. Using mixed method, this article examines the coping strategies employed by households within three communities at risk. Two hundred and seven heads of households residing in Eshiem, Kansawurodo and Whindo were systematically selected to fill in questionnaires, while six key informants comprising chiefs and representatives of flood management institutions were chosen for in-depth interviews. The findings suggest that the commonest coping strategies adopted by residents in all the communities were: temporary vacation of homes, transfer of relevant properties to neighbors and building of flood steps. However, the coping strategies employed by the residents varied by communities, although the majority of them resorted to self-sustaining...

Controlling sewer systems – a critical review based on systems in three EU cities

Abstract: The term Real Time Control (RTC) is widely used to describe all types of control systems in sewer systems. Today the term covers everything from the simplest to the most advanced types of control systems, making it difficult to communicate about sewer system control in a precise manner, as well as search and find specific types of control systems for comparison. Through a survey of implemented control systems in three EU cities today and with the perspectives of current research within the field of sewer system control, the needs for a new control system design framework is identified. With the basis of existing frameworks for control system design, a new time-scale dependent framework is proposed. We believe this comprehensive time-scale dependent framework can help water utilities to retrofit and design new control solutions and facilitate knowledge sharing about existing designs.

A dimensionless approach for the urban-scale evaluation of domestic rainwater harvesting systems for toilet flushing and garden irrigation

Abstract: A dimensionless methodology to evaluate the water saving obtainable from large-scale implementation of domestic rain water harvesting (RWH) systems in urban areas is presented. The methodology combines the use of regressive relationships for water saving evaluation based on the results of the dimensionless rainwater tank water balance and of catchment-wide information obtained from geospatial databases. The adopted RWH scheme included internal use of rainwater for toilet flushing and external use for garden irrigation. An application to a portion of the city of Rome, Italy showed the methodology to allow systematic and accurate evaluation of RWH system performance at the selected urban scale. Results pointed out high water saving potential for toilet flushing ranging between 38–65% for tank sizes within 1–50 m3. Furthermore, more than one third of the systems provided water saving benefit for irrigation larger than 20% by using a 50 m3 tank.

The relevance of sewer deterioration modelling to support asset management strategies

Abstract: Deterioration modelling can be a powerful tool to support utilities in planning efficient sewer rehabilitation strategies However, the benefits of using deterioration models are still to be demonstrated to increase the confidence of utilities toward simulation results This study aims at assessing the performance of a statistical deterioration model to estimate the current condition and predict the future deterioration of a sewer network The prediction quality of the deterioration model GompitZ has been assessed using the extensive data-set of 35,826 inspections performed in the city of Braunschweig, Germany The performance of the statistical model has been compared with the performance of a simple model based only on the condition of observed sewers Results show that the statistical model performs much better than the simple model for simulating the deterioration of the network The findings highlight the relevance of using modelling tools to simulate sewer deterioration and support strategic

An ensemble wavelet bootstrap machine learning approach to water demand forecasting: a case study in the city of Calgary, Canada

Abstract: This paper explores a hybrid wavelet, bootstrap and neural network (WBNN) modeling approach for daily (1, 3 and 5 day) urban water demand forecasting in situations with limited data availability. This method was tested using 3 years of daily water demand and meteorological data for the city of Calgary, Alberta, Canada. The performance of the WBNN method was compared to that of three other methods: traditional neural networks (NN), wavelet NNs (WNN), and bootstrap-based NN (BNN) models. While the hybrid WBNN and WNN models equally provided 1-day lead-time forecasts of greater accuracy than those obtained with other methods, for longer lead-time (3- or 5-day) forecasts the WBNN model alone outperformed the other models. The confidence bands generated using the WBNN model displayed the uncertainty associated with the forecasts.

Illicit intrusion characterization in sewer systems

Abstract: A very important aspect in sewer systems management is represented by the detection of illicit intrusions, which recently supported the development of online sensors for wastewater quality monitoring. The present paper proposes a new methodology for characterizing an illicit intrusion in a sanitary or combined sewer system, using on-line pollutant concentration measurements. The source identification is formulated as an optimization problem, solved combining the hydraulic and quality simulation tool storm water management model (SWMM) with the GALib code. The methodology, which includes a pre-screening procedure useful for complex and large systems, is applied to a literature scheme and a real test-case, showing promising results. An uncertainty analysis is also performed for checking its robustness with respect to inflow uncertainty and in the presence of measurement errors.