Showing papers in "Urban Water Journal in 2011"
TL;DR: In this paper, the authors proposed a methodology based on several leakage-assessment approaches from literature and on water distribution network modeling to assess the benefits that can be achieved by pressure management in Water Distribution Systems, particularly in terms of water production reduction.
Abstract: The occurrence of water losses in Water Distribution Systems is inevitable. Knowing that most of the real losses take place in distribution mains and in service connections, the methodology proposed in this paper is based on several leakage-assessment approaches from literature and on water distribution network modeling. This allows assessment of the benefits that can be achieved by pressure management in Water Distribution Systems, particularly in terms of water production reduction. Moreover, this approach can be useful for cost benefit analysis to help establish the level after which there is no more economic interest in reducing water losses (Economic Level of Leakage). Finally, the results from hypothetical case studies are presented and discussed, assuming the installation of Pressure Reducing Valves at District Metered Areas entry points.
76 citations
TL;DR: In this paper, a fuzzy-based algorithm has been employed that incorporates various uncertainties into different WDS parameters such as roughness, nodal demands, and water reservoir levels to detect and diagnose leakage in WDS.
Abstract: Loss of water due to leakage is a common phenomenon observed practically in all water distribution systems (WDS). However, the leakage volume can be reduced significantly if the occurrence of leakage is detected within minimal time after its occurrence. This paper proposes a novel methodology to detect and diagnose leakage in WDS. In the proposed methodology, a fuzzy-based algorithm has been employed that incorporates various uncertainties into different WDS parameters such as roughness, nodal demands, and water reservoir levels. Monitored pressure in different nodes and flow in different pipes have been used to estimate the degree of membership of leakage and its severity in terms of index of leakage propensity (ILP). Based on the degrees of leakage memberships and the ILPs, the location of the nearest leaky node or leaky pipe has been identified. To demonstrate the effectiveness of the proposed methodology, a small distribution network was investigated which showed very encouraging results. The proposed...
62 citations
TL;DR: A new method for identifying the segments that are formed after the installation and closure of isolation valves in a water distribution network is presented, able to identify segments also when one-way devices are installed in the network.
Abstract: This paper presents a new method for identifying the segments that are formed after the installation and closure of isolation valves in a water distribution network. This method is able to identify segments also when one-way devices are installed in the network. Thanks to its short computing times, the method enables the analysis of real networks which always comprise a large number of nodes and pipes. The numerical examples presented in this paper refer to two real water distribution networks. The first network is a part of a provincial network where two one-way devices are present; the second is a complex urban network without one-way devices. The method was first used to analyse the existing situation in both networks, i.e. the set of segments that are formed as a consequence of the present valve system. The method was subsequently used for the problem of the hypothetic redesign of the isolation valve system in the second urban network, i.e. the search for the optimal positions of the isolation valves...
57 citations
TL;DR: In this paper, an optimisation procedure is developed for calibration of the both types of hydraulic simulation models, demand driven and pressure dependent analyses, by using genetic algorithm, and the suggested calibration procedure is applied on a test network with different consumption scenarios and variables.
Abstract: In this paper, an optimisation procedure is developed for calibration of the both types of hydraulic simulation models, demand driven and pressure dependent analyses, by using genetic algorithm. Variables of pipe roughness coefficient, nodal demand and pipe diameter are investigated for calibration of the hydraulic models. Four scenarios of minimum, normal, maximum and fire consumption are considered for calibration. In addition, the leakage term is incorporated into the hydraulic equations to be able to evaluate the hydraulic situation more realistically in both demand driven analysis (DDA) and pressure dependent analysis (PDA) based models. The suggested calibration procedure is applied on a test network with different consumption scenarios and variables. It is found that the best results are obtained with fire consumption case and both variables of pipe roughness and nodal demand. Leakage consideration reduces the weaknesses of the low flow scenario and also PDA produces lower error values in compariso...
47 citations
TL;DR: In this paper, a bioswale integrating an engineered soil and trees was installed in a parking lot to evaluate its ability to reduce storm runoff, pollutant loading, and support tree growth.
Abstract: A bioswale integrating an engineered soil and trees was installed in a parking lot to evaluate its ability to reduce storm runoff, pollutant loading, and support tree growth. The adjacent control and treatment sites each received runoff from eight parking spaces and were identical except that there was no bioswale for the control site. A tree was planted at both sites. Storm runoff, pollutant loading, and tree growth were measured. There were 50 storm events with a total precipitation of 563.8 mm during February 2007 and October 2008. The bioswale reduced runoff by 88.8% and total pollutant loading by 95.4%. The engineered soil provided a better aeration and drainage for tree growth than did the control's compacted urban soil. The superior performance of the bioswale demonstrated its potential use for large-scale application in parking lots and roadsides to reduce runoff and support tree growth.
46 citations
TL;DR: In this paper, a costbenefit analysis of several static and dynamic solutions to mitigate CSO impact, based on the case-study of the Kessel-Lo catchment in Flanders/Belgium, is presented.
Abstract: In spite of considerable uncertainty reported on the impact of Combined Sewer Overflows (CSO), it is generally acknowledged to not be negligible. Not surprisingly CSO impact is considered – although indirectly – in driving European legislations regarding the wastewater pollution and treatment. Still, when looking at impact reduction, policy makers tend to resort rather to static solutions such as disconnection or the building of storage tanks. On the other hand they often seem to be put off by dynamic measures such as Real Time Control (RTC) of sewage systems because of its perceived complexity. This paper describes a cost-benefit analysis of several static and dynamic solutions to mitigate CSO impact, based on the case-study of the Kessel-Lo catchment in Flanders/Belgium. RTC turned out to be not only the most cost efficient measure for CSO impact mitigation but also the solution offering the most flexibility for further system upgrade.
43 citations
TL;DR: A general framework for a risk-based storm sewer network design, which is capable of taking future risk into account, is proposed and is able to identify the network design balancing the construction cost and flood risk.
Abstract: Storm sewer networks are usually designed under a certain predefined design storm. This paper proposes a general framework for a risk-based storm sewer network design, which is capable of taking future risk into account. In the framework, the flood risk evaluation is located within an optimisation loop. The flood risk is obtained by integrating the area under the probabilistic flood consequence curve, which is identified by simulations of sewer system performance under several design storms. The genetic algorithm is adapted for this specific optimisation problem in order to make the procedure computationally efficient. The framework is applied to the designs of a synthetic network and a real-world network. The results show that the general framework is able to identify the network design balancing the construction cost and flood risk.
36 citations
TL;DR: In this paper, a visual reconnaissance was used to document flowing stormwater outfalls in dry weather and a sampling program was conducted, in combination with decision-making tools, to identify possible sources of illicit discharges.
Abstract: Permit regulations in the U.S. for Municipal Separate Storm Sewer Systems (MS4) require the MS4 to develop a program that detects and eliminates illicit discharges (e.g., improper wastewater connections) into the storm sewer system. Municipalities are interested in cost-effective methods to meet the permit requirements of this federal mandate. Our demonstration project with municipalities in Western New York State evaluated low cost options for illicit discharge trackdown. First, a visual reconnaissance was used to document flowing stormwater outfalls in dry weather. Subsequently, a sampling program was conducted, in combination with decision-making tools, to identify possible sources of illicit discharges. Colorimetric techniques were tested for a number of chemical parameters and the Coliscan Easygel® system was tested for E. coli analysis. Results from these various cost-effective analytical techniques were compared with analysis by standard methods. The E. coli test, in particular, had good precision ...
35 citations
TL;DR: In this article, cognitive mapping is used to elicit perspectives on stormwater problems and solutions in West Auckland, New Zealand, and interviews with key stakeholders reveal three dominant perspectives that underlie contemporary approaches to stormwater management: conventional fixes, low impact solutions and community development.
Abstract: Cognitive mapping is used to elicit perspectives on stormwater problems and solutions in West Auckland, New Zealand. In-depth interviews with key stakeholders reveal three dominant perspectives that underlie contemporary approaches to stormwater management: conventional fixes, low impact solutions and community development. Analysis confirms that these perspectives are diverse and partially conflicting. Traditional engineering approaches to managing urban stormwater generate feedback loops that necessitate continued construction of infrastructure to the detriment of environmental systems. Low impact solutions are environmentally sensitive, but they do not break this feedback loop. Community development could reduce the need for more urban stormwater infrastructure in the long-term but it does not address current adverse impacts of urban growth. Analysis suggests that none of the perspectives in themselves will lead to sustainable outcomes. Rather, the transition to a water-sensitive future requires unders...
29 citations
TL;DR: In this article, a methodology for the inclusion of hydraulics uncertainty in contamination source identification is presented, which is based on a previous contamination source detection model developed by the authors which is further embedded in a statistical framework for quantifying the uncertainty of a contaminated source detection outcome.
Abstract: This study presents a methodology for the inclusion of hydraulics uncertainty in contamination source identification. Current research normally considers the system hydraulics as deterministic and the water quality sensors as ideal. In reality however only a small portion of the hydraulic data is known and most likely only Boolean sensor information of a contamination existence. There is a need to incorporate these considerations in contamination source identification models and to explore their influence on the modelling ability to correctly detect the characteristics of a contamination intrusion. This problem is addressed in this manuscript. The proposed method is based on a previous contamination source detection model developed by the authors which is further embedded in a statistical framework for quantifying the uncertainty of a contamination source detection outcome. The methodology is demonstrated on three example applications of increasing complexity through base runs and sensitivity analyses.
23 citations
TL;DR: In this paper, the conditions under which large solids move in sewers with unsteady flow pulses based on over 1200 experimental runs were determined based on the density of the solid, the slope of the sewer and the flow.
Abstract: At the upstream end of wastewater collection systems, the depth of flow is small and large solids have not disintegrated to any extent. Traditional tractive stress analysis for motion of solids in sewers may not be applicable for large solids which have a larger vertical dimension than the depth of the flow. This paper presents criteria to determine the conditions under which large solids move in sewers which have unsteady flow pulses based on over 1200 experimental runs. The important parameters are the density of the solid, the slope of the sewer and the flow (or in the case of short pulses, the volume of fluid in the pulse). The solids do not move as fast as the fluid. If the duration of the pulse is not sufficiently long, the solid may be picked up and deposited further downstream as the fluid ‘outruns’ the solid.
TL;DR: In this paper, a multidisciplinary Learning Alliance of water sector institutions to embark on a process to identify ways to improve sustainability of the city's water system was identified and a whole-of-system water balance model was used to score the indicators for future scenarios and strategies.
Abstract: Global change pressures such as climate change, water scarcity, population growth, full urbanisation of catchments and rising energy costs may increasingly affect the urban water system of Tel Aviv. These challenges formed the incentive for a multidisciplinary Learning Alliance of water sector institutions to embark on a process to identify ways to improve sustainability of the city's water system. Sustainability indicators were identified and a whole-of-system water balance model (AquaCycle) was used to score the indicators for future scenarios and strategies. Strategies included rainwater harvesting, stormwater use, permeable pavements, and wastewater reuse. The effect of the strategies on total water imported into the city was a reduction of 10% by rainwater harvesting and 32% by wastewater reuse at cluster scale. The latter strategy reduced energy consumption from 2.89 kWh per m3 of volume of water used (import + reuse) in the current situation to 2.45 kWh per m3.
TL;DR: In this paper, the authors analyzed the consumption of and the expenditure on chemicals and energy at Oslo's water treatment plants and wastewater treatment plants over time, and found that chemicals for water and chemicals for wastewater treatment, on an average account for
Abstract: Adopting a systems-approach to an urban water and wastewater system, while applying a triple bottom line strategy to management, entails a careful analysis of all the sub-systems and components thereof with a view to improving service levels, optimising expenditure, augmenting investments, and also reducing the life-cycle environmental impacts associated with setting up, maintaining and operating the system The scope for optimising expenses is system-wide, though it varies from one sub-system to another, depending on inherent lock-ins and external factors beyond the direct control of the water and wastewater utility Optimising the consumption of energy and chemicals and improving the cost-efficiency thereof, is always on the agenda of water treatment plants (WTPs) and wastewater treatment plants (WWTPs) This paper analyses the consumption of and the expenditure on chemicals and energy at Oslo's WTPs and WWTPs over time Energy and chemicals for water and wastewater treatment, on an average account for
TL;DR: In this paper, the characteristics of pollutants transported by stormwater and wastewater collection networks in two urban watersheds were discussed, along with an estimation of pollutant fluxes discharged into the Gohards River.
Abstract: A two-year study of pollutants in both the stormwater and wastewater of urban watersheds has been conducted in Nantes (France). The present paper discusses the characteristics of pollutants transported by stormwater and wastewater collection networks in two urban watersheds. A physicochemical characterisation of the effluents was performed, along with an estimation of pollutant fluxes discharged into the Gohards River. Suspended solids (SS), trace metals, polycyclic aromatic hydrocarbons (PAHs) and pesticides were studied. SS, Zn, Cu and glyphosate were the main pollutants in stormwater and wastewater. In the watersheds examined, the pyrolitic origin of PAHs (mainly from traffic) was determined through ratios, with fluoranthene and pyrene being predominant. Despite a reduction in the use of pesticides in Nantes Metropolitan area, herbicides containing glyphosate were still detected in stormwater. It should be noted that this herbicide is widely used by homeowners, a fact that may explain its occurrence in...
TL;DR: In this article, a hierarchy of LIUDD principles has been developed as a foundation for policy development in statutory and non-statutory plans and guidelines, accompanied by practical implementation methods using sustainable technologies in a local context.
Abstract: One method of enhancing the health of receiving water ecosystems is to ensure that local plans and practices guiding urban development are underpinned by appropriate design principles. This paper reports on a policy and practices framework developed in New Zealand, and investigates the uptake and implementation of Low Impact Urban Design and Development (LIUDD). A hierarchy of LIUDD principles has been developed as a foundation for policy development in statutory and non-statutory plans and guidelines. Each principle is accompanied by practical implementation methods using sustainable technologies in a local context. Greenfield developments in urban growth areas in the Netherlands, Australia and New Zealand are assessed with respect to elements of the framework. The assessments show that the LIUDD principles are relevant internationally across greenfield developments of similar town and catchment scales. Application of the principles can inform decision makers so that they become more critically aware of ...
TL;DR: In this article, the authors report on New Zealand case studies of Long Bay (North Shore), Flat Bush (Manukau) and Mapara Valley (Taupo) using low impact urban design and development.
Abstract: Where receiving-water health is the driver for a change from conventional urbanisation, the logical design and management framework is the catchment (river-basin). New Zealand examples of catchment-based structure planning use a common approach that meets the objectives of the practice of Low Impact Urban Design and Development (LIUDD). One key ingredient is the clustering of buildings in catchment ‘middle lands’ removed from environmentally sensitive areas such as erosion-prone escarpments, ridges, riparian corridors and wetlands. This facilitates additional open space creation enabling ecosystem protection or restoration, the optimisation of landscape qualities and recreational opportunities. Using New Zealand case studies of Long Bay (North Shore), Flat Bush (Manukau) and Mapara Valley (Taupo) this paper reports on progressive learning across municipalities, developers and communities that have used the LIUDD approach. It demonstrates progress towards merging Integrated Catchment Management (ICM) plann...
TL;DR: In this article, it is demonstrated that a good understanding of the system from raw water to tap is needed if cost effective models of appropriate fidelity are to be produced, and that appropriate systems models can incorporate, through empirical relationships, raw water quality variations based on river flow predictions, aspects of unit process management decision making variables as well as distribution system characteristics.
Abstract: Tighter regulatory standards for trihalomethanes in drinking water have been introduced in many countries in response to improved epidemiological evidence. This has led to the need to model better the THM concentrations in water distribution systems in order to manage efficiently economic, chemical and microbiological factors. THM modelling is a challenging process given the complex chemistry and dependence on river catchment, water treatment works and distribution system characteristics. It is demonstrated that a good understanding of the system from raw water to tap is needed if cost effective models of appropriate fidelity are to be produced. For appropriate systems models can incorporate, through empirical relationships, raw water quality variations based on river flow predictions, aspects of unit process management decision making variables as well as distribution system characteristics. In many systems model fidelity and hence efficient management is constrained by a lack of knowledge of system resp...
TL;DR: In this paper, an analysis of the inflows of materials and energy into the network and the corresponding outflows, facilitates the determination of the environmental impacts associated with the life-cycle stages of the pipeline network, and an examination of how the contributions of each of these phases to the whole, changes as the network ages and progresses towards saturation.
Abstract: Any saturated urban wastewater pipeline network has an ageing mix of pipelines of different lengths, diameters and materials of construction. Each of these pipe-lengths has its own life-cycle which encompasses the material production and pipe fabrication, installation, operation and maintenance during the use phase, rehabilitation and repair and finally retirement from service. An analysis of the inflows of materials and energy into the network and the corresponding outflows, facilitates the determination of the environmental impacts associated with the life-cycle stages of the pipeline network, and an examination of how the contributions of each of these phases to the whole, changes as the network ages and progresses towards saturation. The forecast of the future flows of materials which again, is highly interlinked with the historic flows provides insight into the likely future environmental impacts. The authors, in this paper, present a general methodology which can be applied with some tailor-making, ...
TL;DR: In this article, an assessment was done on the microbiological quality of water in hand-dug wells in urban communities in Kumasi, Ghana and the results showed a stronger influence of poor sanitation and improper placement of wells on water quality compared to improvements made from lining and protection of wells.
Abstract: Assessment was done on the microbiological quality of water in hand-dug wells in urban communities in Kumasi, Ghana. A total of 256 water samples were taken from eight wells and examined for faecal coliforms, enterococci and helminths. High contamination levels were recorded in the wells, more so in the wet season, with faecal coliforms levels between 6.44 and 10.19 log units and faecal enterococci between 4.23 and 4.85 CFU per 100 ml. Influence on protection and lining of wells on water quality was not pronounced but mechanization reduced contamination significantly by about 3 log units. This study shows a stronger influence of poor sanitation and improper placement of wells on water quality compared to improvements made from lining and protection of wells. In the race to increase access to drinking water in poor urban settlements, quality of groundwater could be a major barrier, if provision of drinking water is not matched with improvements in sanitation and urban planning.
TL;DR: In this article, two hydraulic software simulation tools and two stormwater quality model approaches are compared to assess CSO behaviour and the impact of different modelling approaches on the estimation of spilled pollutant loads in long-term simulations for an urban catchment area.
Abstract: In many countries traditional simple design approaches for combined sewer overflow (CSO) structures and storage tanks are used in general practice, neglecting the significant variability observed in real systems. In this paper, two hydraulic software simulation tools and two stormwater quality model approaches are compared to assess CSO behaviour and the impact of different modelling approaches on the estimation of spilled pollutant loads in long-term simulations for an urban catchment area. A good coherence of the two runoff models is observed. The more complex stormwater quality model approach leads to significantly lower TSS interception ratios for smaller specific storage tank volumes. For both the hydraulic CSO indicators and TSS interception ratios an important annual variability is observed. Therefore, using single design value approaches or short rainfall time series in modelling can lead to significant impact on the design ratio of storage tank and CSO structures.
TL;DR: In this article, an online survey of urban water management professionals in The Netherlands investigated professionals' receptivity to innovations and found that professionals are well aware of innovative technologies and expect application of these technologies in the near future.
Abstract: Despite widespread acknowledgement of the need for more sustainable urban water management and the availability of reliable technologies, implementation of new technologies remains limited to small-scale demonstration projects. The receptivity of professionals to innovations seems a determining factor for application of new technologies. An online survey of urban water management professionals in The Netherlands investigated professionals' receptivity to innovations. The results showed that professionals are well aware of innovative technologies. They expect application of these technologies in the near future. However, in general the appreciation of the potential contribution of these technologies to sustainability was moderate.
TL;DR: In this article, material flow analysis was applied to model different scenarios which help better identify and quantify water supply and wastewater pollution problems in the city of Kumasi, Ghana, and showed that despite a relative abundance of water resources in the surrounding area of the city, drinking water consumption will remain at a low level.
Abstract: Material flow analysis was applied to model different scenarios which help better identify and quantify water supply and wastewater pollution problems in the city of Kumasi, Ghana. Results show that despite a relative abundance of water resources in the surrounding area of the city, drinking water consumption will remain at a low level (from 49 ± 4 l/cap/day in 2006 to 59 ± 5 l/cap/day in 2015). Changing sanitation practices to using more flush toilets will require significantly more water if these toilets are to be used adequately. The water–nutrient balance shows that total nitrogen (N) and phosphorus (P) outputs of the modelled area are 10 times higher than system inputs, most of this being attributed to human wastes from sanitation. A number of possible measures to reduce nutrient flows into water bodies were identified and quantified, showing the usefulness of the applied model in providing estimates for municipal decision-makers.
TL;DR: In this paper, the authors proposed the concept of water metres to stimulate debate around further reduction in demand for potable reticulated water, and argued that the introduction of this concept will encourage greater on-site water capture for onsite use, and provide commensurate reductions in demand from bulk supplies for non-potable suburban use.
Abstract: With increased affluence and urbanisation a reliable water supply is regarded as a basic right of urban people in many countries. This has resulted in a paradigm shift in community attitudes to water, and governments increasingly encourage citizens to rethink attitudes to water use as one ‘tool’ to reduce demand. While a range of ‘tools’ are used to encourage water availability (dams, recycling, desalination, water efficiency), in urban centres conservation remains heavily reliant on water restrictions to deliver short-term reductions. To stimulate debate around further reduction in demand for potable reticulated water we propose the concept of ‘water metres’ (the distance water is transported from its point of capture to consumption). The concept parallels ‘food miles’. We argue that the introduction of this concept will encourage greater on-site water capture for on-site use, and provide commensurate reductions in demand for potable water from bulk supplies for non-potable suburban use.
TL;DR: In this paper, a new series of experimental measurements were conducted in actual sewers in order to investigate the influence of the major factors affecting sampling, such as water velocity, sampling velocity, and sampling tube location relative to the flow direction.
Abstract: Pollutant quantification offers a wide range of applications in the field of water resources. With respect to sewage, a key issue is sample representativeness, as samples are often collected under technically challenging conditions. A new series of experimental measurements were conducted in actual sewers in order to investigate the influence of the major factors affecting sampling. Such factors include water velocity, sampling velocity, sampling tube location and orientation of the sampling point relative to the flow direction. Results show that the influence of these factors remains within 5% of the mass of the total suspended solids concentrations, meaning that in most practical applications, this influence may be neglected.
TL;DR: In suburban Belgrade, there are some 200 local water supply systems which are not connected to either the Belgrade Water Supply System or to supply systems operated by municipal utilities.
Abstract: In suburban Belgrade, there are some 200 local water supply systems which are not connected to either the Belgrade Water Supply System or to supply systems operated by municipal utilities. The small systems in Belgrade suburbs are either operated by local municipality (local government) or even by the group of local citizens who have neither technical capability nor financial resources to do it properly. Roughly 200,000 of Belgrade's inhabitants obtain their drinking water from these water supply systems. The water quality delivered by these local water supply systems is often compromised in terms of microbiological, physical and/or chemical compliance with drinking water standards in addition to the general lack of strategy on water safety plans and risk assessment. WHO Guidelines on water quality standards as well as the recommendations on safety plans and whole risk assessment are strictly respected in the main (central) Water Supply System in Belgrade. Most frequently, elevated concentrations of ammon...
TL;DR: In this paper, the effluent and influent of a constructed wetland treating separately collected greywater were subjected to liquid/liquid extraction with dichloromethane as well as to solid phase extraction.
Abstract: Effluent and influent of a constructed wetland treating separately collected greywater were subjected to liquid/liquid extraction with dichloromethane as well as to solid phase extraction. Extracts were analysed by gas chromatography/mass spectrometry. More than 80 organics were tentatively identified or roughly characterised in the raw greywater by their mass spectra. A lower number (26) of organic compounds was tentatively identified in the constructed wetland's effluent. Major compounds found in at least one extract of the effluent were an alkane, a squalene isomer, hexadecanoic acid, two not exactly identified phthalates, tris-chloropropyl phosphate, an acephylline derivative and an unidentified nitrogenous heterocycle. The persistent flame retardant tris-chloropropyl phosphate and a couple of phthalates found in the biologically treated greywater are of concern when biologically treated greywater will be reused for high quality demand. Most of the trace organics found in the greywater samples were re...
TL;DR: A review of the state of technology for renewal of force mains is presented in this article, where the authors identify several needs, including the need for rational and common design approaches for rehabilitation systems, quality assurance/quality control procedures, and better practices for operation and maintenance.
Abstract: This paper presents the results of a review of the state of technology for renewal of force mains. Force mains are critical components of many sewer collection systems with significant environmental and cost consequences for failure. The review identified several needs, including the need for rational and common design approaches for rehabilitation systems, quality assurance/quality control procedures, and better practices for operation and maintenance. The difficulty in assessing the condition of sewer force mains, leaving many owners with questions about the integrity of their systems, and the limited amount of technologies available for renewing a deteriorated main, has limited the amount of renewal work in the past. Most of the renewal activity has involved complete replacement of the force main. As the nation's force mains age further, greater emphasis must be placed on finding cost-effective ways to renew these critical assets. Fortunately, new products and technologies are now emerging for conditio...
TL;DR: In this article, the authors developed a methodology to test existing stormwater draina, which is used to manage stormwater runoff in rapidly developing urban watersheds, in order to preserve water quality.
Abstract: Managing stormwater runoff is crucial to preserving water quality in rapidly developing urban watersheds. The objective of this study was to develop a methodology to test existing stormwater draina...
TL;DR: Wang et al. as discussed by the authors used the example of Yulin city in northwest China to assess the spatio-temporal characteristics and driving forces of annual river flow changes based on the long-term time series of hydrological data from 1956 to 2005, to analyse annual flow in four main rivers (Kuye River, Tuwei River, Wuding River and Jialu River).
Abstract: Climate change and human activities have changed a number of characteristics of river flow in the northwest of China. Numerous problems such as water resource shortage, drying up of rivers, water pollution are the direct consequences of these changes. In this paper, we used the example of Yulin city in northwest China to assess the spatio-temporal characteristics and driving forces of annual river flow changes. Our research was based on the long-term time series of hydrological data from 1956 to 2005, to analyse annual flow in four main rivers (Kuye River, Tuwei River, Wuding River and Jialu River). The river flow depends upon the runoff characteristics of the river catchment, therefore we used variation ratio, variation index, unevenness, Runoff-Concentration Degree (RCD) and Runoff-Concentration Period (RCP) to determine the change in runoff characteristics of the four main rivers flows of the Yulin city. We tested the tendency of runoff by the Mann-Kendall non-parameter statistical method to obtain the...
TL;DR: In this article, the authors used the same type of analysis used for grate inlets, and found that decks' minimum "worst case" permeability is higher than common natural rainfall intensities and at least as high as that of competing permeable surfacing materials.
Abstract: Decks or boardwalks are frame structures with plank surfaces for bearing pedestrian traffic. They offer a potential addition to the list of surfacing materials that maintain perviousness of land cover in the midst of urban development. In this study, using the same type of analysis used for grate inlets, it was determined that decks' minimum ‘worst case’ permeability is higher than common natural rainfall intensities and at least as high as that of competing permeable surfacing materials. Cost analysis demonstrated that the cost of deck construction is comparable to that of competing permeable surfacing materials. Diverse case studies illustrate that there is experience with decks in a variety of urban settings. Therefore it is recommended that decks be on any list of surfaces available for effectively reducing urban impervious cover, while continuing to limit their application to the traffic types for which they are suited.