Intermittent Water Distribution Systems Research Articles

Placement Strategies for Water Quality Sensors Using Complex Network Theory for Continuous and Intermittent Water Distribution Systems

AbstractWater quality sensors are used to detect contamination in water distribution systems (WDSs) to help supply safe and quality drinking water to society. However, identifying the optimal location to place sensors is still an open challenge. Many approaches have been proposed in literature to solve this problem. Complex network theory‐based approaches (CNW) to sensor placement are simple, easy to implement, take less computational time even for large‐scale networks, and do not require calibrated hydraulic and water‐quality models. However, existing CNW methods perform well for only a subset of common objectives. Optimization‐based approaches offer better placement but are computationally costly and require detailed knowledge of the WDS. We proposed a new method, “EQ‐Water,” to identify the locations to place water quality sensors for continuous and intermittent WDS with variable demand patterns. EQ‐Water is based on complex network theory, but uses minimal additional hydraulic information. We validate the performance of EQ‐Water on four real networks: BWSN 1, BWSN 2, JPN, and D2B networks. We have compared the performance with a number of approaches from literature, including the popular TEVA‐SPOT tool. The comparison is based on the four objective functions, Z1–Z4, which are commonly used, and also on a weighted cumulative objective function. Our results indicate that EQ‐Water is among the top three methods for BWSN 1, JPN and D2B when using diverse weights for the objective functions, and it shows median performance for BWSN 2. We also observe consistently superior performance against other CNW, and it is competitive with simulation‐based approaches while taking lesser time and effort.

A Simplified Methodology for Optimal Location and Setting of Valves to Improve Equity in Intermittent Water Distribution Systems

In this paper, a simplified methodology to increase the water distribution equity in existing intermittent water distribution systems (WDSs) is presented. The methodology assumes to install valves in the water distribution network with the objective to re-arrange the flow circulation, thus allowing an improved water distribution among the network users. Valve installation in the WDS is based on the use of algorithms of sequential addition (SA). Two optimization schemes based on SA were developed and tested. The first one allows identifying locations of gate valves in order to maximize the global distribution equity of the network, irrespectively of the local impact of the valves on the supply level of the single nodes. Conversely, the second scheme aims to maximize the global equity of the network by optimizing both location and setting (opening degree) of control valves, to include the impact of the new flow circulation on the supply level of each node. The two optimization schemes were applied to a case study network subject to water shortage conditions. The software EPA Storm Water Management Model (SWMM) was used for the simulations in the wake of previous successful applications for the analysis of intermittent water distribution systems. Results of the application of the SA algorithms were also compared with those from the literature and obtained by the use of the multi-objective Non-Dominated Sorted Genetic Algorithm II (NSGA II). The results show the high performance of SA algorithms in identifying optimal position and settings of the valves in the WDS. The comparison pointed out that SA algorithms are able to perform similarly to NSGA II and, at the same time, to reduce significantly the computational effort associated to the optimization process.

Multivariate analysis of the pressure variation in intermittent water supply systems and the impact on demand satisfaction

Abstract In intermittent drinking water distribution systems, large volumes of the water are wasted due to leaks in the distribution networks. Similarly, user service is not always satisfied in the time required to fill the storage, nor with sufficient pressure. Hence the importance of this study. Measuring the variability of pressure in the distribution network and determining the factors that influence the definition of a sufficient minimum hours of service, is a first step to change to a continuous service 24/7, in order to minimize the volumes of lost water and meet demand. In total, 347 pressure sensors were placed in a network to detect changes in pressure and obtain data for 3 years. This study presents a new approach to determine the operating policy of the operating agency that provides the service intermittently. Two objectives are pursued: pressure variability – to minimize leaks – and define the minimum hours of service. The analysis was performed using multivariate statistical techniques, including principal component analysis, correlation matrix and ANOVAs, to explore the association between objectives. The results obtained show that the pressure distribution has a Gaussian behavior and that the hours of service have a Poisson distribution.

Optimal Location of Valves to Improve Equity in Intermittent Water Distribution Systems

This paper proposes a methodology to increase the level of water distribution equity in intermittent water distribution networks (WDNs) with users equipped with private tanks. The methodology makes it possible to identify optimal valve locations and settings to improve the distribution of water among users by rearranging the flow circulation in the network. Two optimization schemes based on the use of NSGA II were developed. The first scheme aims at maximizing the global distribution equity of a WDN through installation of valves fully closed. The second scheme looks also at the levels of supply of the individual nodes of a WDN and includes optimization of both locations and settings of control valves. The two optimization schemes are applied to the case study of a WDN in northern Italy considering a scenario of water shortage. The EPA’s Storm Water Management Model software was used for the pressure-driven simulation of an intermittent WDN. Results of the application of the two optimization schemes highlight the potential for an increase in the global equity of the WDN by installation of a few valves. However, some nodes of the WDN were penalized by the new flow circulation as obtained by solutions provided by the first scheme. In fact, these nodes unacceptably worsen their condition compared to the no-valve scenario. Conversely, solutions obtained with the second scheme allowed demand satisfaction levels to not worsen compared to the no-valve scenario for all nodes.

Analysis and Design of Continuous Water Distribution System against Existing Intermittent Distribution System for Selected Area in Pandharpur, M.S., INDIA

In infrastructural development the public drinking water distribution network which includes pipes, bents, valves, pumps, tanks etc. is one of the major investments. The design, modeling of distribution network with efficient outcome is an important task. Therefore, the present study is aimed at design of continuous as well as intermittent water distribution systems with adequate water pressure with the use of WaterGEMS Vi8 software. The study is carried out for Manisha Nagar and Padmavati in Pandharpur, Maharashtra. The system comprised of a pipeline network consisting of one source node and several demand nodes is considered to find its optimal geometrical layout which delivers known demands from source to consumers over a long period of time. The effect of forecasted resident population and floating population on demand, head loss gradient, pressure gradient is analyzed. This study is carried out for immediate stage - Year 2021, intermediate stage - Year 2036 and final stage - Year 2051. From the analysis it is observed that, as population increases from year 2021 to 2051, the demand, head loss gradient and pressure development increases.

A multi-objective optimization model for operation of intermittent water distribution networks

Abstract Intermittent operation of water distribution networks (WDNs) is an undesirable yet inevitable strategy under some circumstances such as droughts, development, electricity blackouts, and water pollution, mostly in developing countries. Intermittent utilization of WDNs poses several disadvantages encompassing water quality degradation, deterioration of the water-distribution system, and extra operational and maintenance costs due to frequently interrupted supply, unfair water distribution among consumers, and reduction of system serviceability. This paper proposes a multi-objective optimization model to address the negative consequences of intermittent water shortages. The model is intended to maximize the quantitative and qualitative reliability and the fairness in water supply, and to minimize the frequency of supply interruption. The developed model also considers pragmatic limitations, water quality, water pressure, and supply reservoir's constraints to plan the operation of intermittent water distribution systems under water shortage. The model's efficiency is tested with a WDN in Iran and compared with a standard operation policy (SOP) for water distribution. According to the evaluated efficiency criteria concerning reliability, resiliency, and vulnerability of water quality and quantity of water supply, the developed model is superior to the SOP rule and improves the performance of the network under intermittent operation. In addition, the results demonstrate there is a tradeoff between the uniformity of water distribution and the frequency of supply interruption that shows operators’ and customers’ conflicting priorities.

Using EPA-SWMM to simulate intermittent water distribution systems

ABSTRACTEPA Storm Water Management Model (EPA-SWMM), developed for the analysis of urban drainage systems, was used in a novel way to simulate the filling phase in intermittent water distribution systems. Firstly, the model was validated against field experimental observations from a filling test in a real water distribution network in Sicily. Then, model results were compared to those obtained by the use of a model based on the theory of the rigid water column, revealing the potential and limitations of the two approaches. The obtained results open new perspectives for the use of EPA-SWMM for the analysis of processes occurring in intermittent water distribution systems.

Assessment of domestic consumption in intermittent water supply networks: case study of Puerto Ayora (Galápagos Islands)

Intermittent water distribution systems are a stark reality in developing countries. Puerto Ayora, the centre of tourism of the Galapagos Archipelago, is not an exception, with its population and tourists suffering from scarce water resources. However, the extreme per capita consumptions, well above those in 24/7 supply situations in many other countries, contradict the (sense of) scarcity. In this study, 18 water meters were installed and a water-appliance diary was carried out in 15 randomly selected households in Puerto Ayora. The aim was to determine and analyse domestic water consumption, as well as the diurnal patterns, also by verifying per capita figures ranging from 40 to 380 litres per capita per day from a previous study. Also, the aim was to find a correlation between the consumption and schedules of distribution conducted by the municipality. The paper also elaborates on typical household appliances used, and gives an insight about a wide range of domestic demands in a predominantly water-scarce area. The conclusions indicate no influence of the specific intermittency patterns to the specific demand, but rather a wide range of different lifestyles, the possible presence of informal accommodations and excessive wastage.

Equity in water supply in intermittent water distribution networks

AbstractEquity in water supply is one of the major problems faced in intermittent water distribution systems. A new index ‘uniformity coefficient’ is introduced to measure the equity in distribution of water within the network, which may be useful for performance evaluation of water distribution networks (WDNs). An iterative head‐driven analysis technique is developed to compute the uniformity coefficient of a network. The effect of various design parameters of WDN on the uniform coefficient is studied. The results indicate that equity in water supply is significantly affected by the location of the tank and layout of the network. The equity in water supply can be improved in an existing network by staggered supply.

Impacts of supply duration on the design and performance of intermittent water distribution systems in the West Bank

This paper analyzes the intermittent water distribution system in the West Bank, Palestine. It quantifies the impacts of reduced supply duration on the hydraulics and costs of water distribution. It shows that designing systems based on intermittent supply criteria implies increasing the diameters of pipes significantly, which is expensive and infeasible. The paper recommends that studying the local conditions should precede the design of new systems to avoid reduced supply duration and related negative impacts. In addition, improving governance, revising tariffs, reducing leakage, saving water, involving the private sector, and improving water diplomacy should be considered in any water policy reform.

Leakage–pressure relationship and leakage detection in intermittent water distribution systems

Field investigations were conducted to identify the relationship between leakage rate and pressure in selected areas of the water distribution system of the Holy City of Makkah, Saudi Arabia. Noise correlators were used to detect leaks in areas where the water leakage exceeded 20% of the total water supplied. The leakage rate was found to be related to pressure raised to the n th power. The value of n was found to be 0.50 for the network of asbestos-cement pipes and 1.16 for the network of mixed pipes. Considering the age of the network, the leakage rate was found to be linearly related to the age of the network and related to pressure raised to the 1.10 power. About 63.15% of the leaks were found to be at the property connections. The rest were either in the service lines or at the junction of the service lines with the property connections. The galvanized iron property connections were found to be highly corroded, with circular holes and/or longitudinal corrosion cracks.

Managing urban water supplies in developing countries – Climate change and water scarcity scenarios

Urban areas of developing countries are facing increasing water scarcity and it is possible that this problem may be further aggravated due to rapid changes in the hydro-environment at different scales, like those of climate and land-cover. Due to water scarcity and limitations to the development of new water resources, it is prudent to shift from the traditional ‘supply based management’ to a ‘demand management’ paradigm. Demand management focuses on measures that make better and more efficient use of limited supplies, often at a level significantly below standard service levels. This paper particularly focuses on the intermittent water supplies in the cities of developing countries. Intermittent water supplies need to be adopted due to water scarcity and if not planned properly, results in inequities in water deliveries to consumers and poor levels of service. It is therefore important to recognise these realities when designing and operating such networks.The standard tools available for design of water supply systems often assume a continuous, unlimited supply and the supplied water amount is limited only be the demand, making them unsuitable for designing intermittent supplies that are governed by severely limited water availability. This paper presents details of new guidelines developed for the design and control of intermittent water distribution systems in developing countries. These include a modified network analysis simulation coupled with an optimal design tool. The guidelines are driven by a modified set of design objectives to be met at least cost. These objectives are equity in supply and people driven levels of service (PDLS) expressed in terms of four design parameters namely, duration of the supply; timings of the supply; pressure at the outlet (or flow-rate at outlet); and others such as the type of connection required and the locations of connections (in particular for standpipes). All the four parameters are calculated using methods and techniques that recognise the relationship between outflow at a water connection and the pressure experienced at that connection. The paper presents a case study where it is demonstrated that the new guidelines can provide an equitable and acceptable level of service throughout the design horizon of the project.

Modelling the risk of contaminant intrusion in water mains

The contamination of water distribution systems is widely recognised in the case of intermittent water supplies, where pipes are empty for many hours each day and thus under negligible or zero pressure. This allows contaminants from pollution sources such as sewers, open drains and surface water bodies to enter into the water distribution pipes through leaks and cracks during non-supply hours. In developing countries, where water supply is intermittent, contamination frequently occurs to the distribution network at unacceptably high levels, posing a threat to public health. The urban poor suffer most from contaminated water supplies and also suffer a far greater health burden, related in part to the consumption of poor quality water. There are no tools currently available to assist engineers in identifying the risks associated with contaminant intrusion into intermittent water distribution systems. This paper introduces a new tool called integrated risk assessment of water distribution systems (IRA-WDS). It is anticipated that the application of such tools will enable engineers to manage water quality more effectively by developing appropriate control measures to minimise the risks of contaminant intrusion. This paper summarises details of the mathematical models that form the basis of IRA-WDS and also describes the application of the tool to a real case study in India. The outputs from IRA-WDS are risk maps showing the risk of contaminant intrusion into the various parts of the water distribution system and an understanding of the main factors that contribute to risk. These risk maps will be invaluable to decision makers in that they can provide a guide to prioritise the operation and maintenance strategy in order to improve water quality.

Intermittent Water Supply under Water Scarcity Situations

This paper describes the recently developed ‘Guidelines for the design and control of intermittent water distribution systems’. These guidelines outline a new approach to the design of urban water distribution systems for developing countries in order to maintain adequate and equitable supplies under the common conditions of water resource shortage. The guidelines are novel in that they recognise the reality of intermittent supply and hence provide new methods of analysis and design, appropriate for such systems. Design objectives specifically tailored to intermittent systems are developed and drive the design process. These objectives are expressed in terms of equity in supply, adequate pressure at water connections and duration or time of supply that are convenient to the consumers. The modifications required to model such systems have been incorporated into a new network analysis simulation tool coupled with an optimal design tool.

IRA-WDS: A GIS-based risk analysis tool for water distribution systems

This paper presents the development of a new software tool IRA-WDS. This GIS-based software predicts the risks associated with contaminated water entering water distribution systems from surrounding foul water bodies such as sewers, drains and ditches. Intermittent water distribution systems are common in developing countries and these systems are prone to contamination when empty. During the non-supply hours contaminants from pollution sources such as sewers, open drains and surface water bodies enter into the water distribution pipes through leaks and cracks. Currently there are no tools available to help engineers identify the risks associated with contaminant intrusion into intermittent water distribution systems. Hence it is anticipated that IRA-WDS will find wide application in developing countries. The paper summarises the details of the mathematical models that form the basis of IRA-WDS. It also describes the software architecture, the main modules, and the integration with GIS using a tight coupling approach. A powerful GUI has been developed that enables data for the models to be retrieved from the spatial databases and the outputs to be converted into tables and thematic maps. This is achieved seamlessly through DLL calling functions within the GIS. This paper demonstrates the application of the software to a real case study in India. The outputs from IRA-WDS are risk maps showing the risk of contaminant intrusion into various parts of the water distribution system. The outputs also give an understanding of the main factors that contribute to the risk.

Guidelines for the design and control of intermittent water distribution systems

Water supply in many towns and cities is intermittent, with low and uneven pressures around the system. The guidelines described here help engineers design systems with a more equitable distribution of available water within the constraints of intermittent water supply.