mohammadreza jalili ghazizadeh

In the realm of hydraulic modeling for water distribution networks, the calibration process plays a pivotal role. Calibration involves precise adjustments to align a model with observed data. However, when the measured data is scarce, the calibration process becomes challenging. In such cases, laboratory models prove valuable for simulating real-world conditions. Variability in parameters like pipe dimensions, length, roughness coefficients, and nodal demand as well as nodal elevations often leads to disparities between computer-based model outcomes and reality. Despite extensive research on computer-based models, laboratory water distribution network models and their calibration have received relatively limited attention due to the challenges and costs associated with them. In this study, a laboratory model of a water distribution network was constructed and subjected to hydraulic calibration. Roughness coefficients and minor head losses within the network were determined using a meta-heuristic method. Then, pipe roughness coefficients for polyethylene pipes were assessed and compared with values from scientific references. In the following, hydraulic validation of the network was conducted using the water quality simulation of a conservative substance. This approach illustrates the level of concurrence of flow ratios in the network pipes between the model and reality.The laboratory network was made of PE40 and consists of a square looped system with 1-meter pipe lengths, employing a 1000-liter tank to maintain a constant water head. This research was conducted in three stages. In the first stage, network calibration was performed using piezometric pressure and output flow data. Roughness coefficient and pipe minor head loss coefficients were selected as decision variables. The objective function was defined to minimize the total weighted difference in piezometric head and discharge between the model and reality. In the second stage, validation was performed based on pressure and output flow data. In the third stage, the network's hydraulic validation with respect to pipe flow rates was performed through the modeling of a conservative substance. This is because the dissolution of a conservative substance occurs solely due to mixing at nodes and flow division, allowing it to represent the correspondence of flow ratios in network pipes between the model and reality. In this research, pressure data was recorded using piezometers, and salt concentration was calculated using TDS (Total Dissolved Solids) sensor. After performing the optimization, a value of 0.008 was obtained for the Darcy-Weisbach friction coefficient (ɛ), This value aligns well with the assumption of new pipes in the network, in agreement with previous research (e.g., 0.050 by The Plastics Pipe Institute, 2008, and 0.070 by Padilla et al., 2013). Also, values of 1.20 and 0.89 were obtained for the minor loss coefficients of 0.5 and 1-meter pipes, respectively. Furthermore, the optimized minor loss values effectively reflect differences attributed to the number of connections in the 0.5 and 1-meter pipes, falling within recommended scientific ranges. Notably, unlike previous field studies, this research uniquely focuses on a laboratory model.After hydraulic calibration and validation using pressure and output flow data, further validation was conducted using the water quality model. The saltwater solution was injected at a specific point in the network, and the TDS quality parameter was measured at the two points in the network. Subsequently, utilizing the TDS values and the established relationship between TDS and salt concentration calculated in the laboratory, the salt concentration at the location of two sensors was determined. It's worth mentioning that the network's water supply contained dissolved solids. Subsequently, initial and injection concentrations were applied to the model and, the simulation was performed. A comparison of salt concentration results at two sensor locations revealed an 8.5% error in the first experiment and 2.5% in the second, confirming excellent agreement between the laboratory and computer-based network hydraulic model.

The entry of large volumes of industrial effluents containing organic pollutants and dyes into water has made pollution an important issue and led to more attention being paid to advanced oxidation processes for industrial wastewater treatment. Cavitation, due to its ability to produce active free radicals, is a technique that has been considered to increase the efficiency of water and wastewater treatment processes in order to remove organic chemical compounds and decompose pollutants resistant to biological decomposition. The purpose of this research is to use hydrodynamic cavitation to remove the methyl orange dye and optimize the operating parameters for color removal efficiency. For this purpose, cavitation was produced through the use of a pump and an orifice plate with a 4 mm diameter hole, and methyl orange with a concentration of 2 mg/L was tested at each stage. In the following, the effect of operating parameters, including pressure in the range of 0.5 to 6.5 bar, temperature in the range of 8 to 40 °C, pH in acidic, neutral, and alkaline conditions after 135 minutes was determined to achieve the maximum decolonization in optimal conditions. In this study, optimal conditions for achieving the highest removal efficiency (51.7%) were obtained at an inlet pressure of 5.5 bar and a cavitation number of about 0.14 (Ca≈0.14). The results of this investigation showed that the decomposition and removal of methyl orange dye using the hydrodynamic cavitation method is sensitive to the pH of the solution, especially in acidic conditions, which are more suitable conditions for the production of hydroxyl radicals than in alkaline conditions, and has higher efficiency in acidic conditions. Also, increasing the temperature of the solution due to the effect on the saturated vapor pressure will increase the decolonization rate.

To estimate the rate of leakage in the water distribution networks, the International Water Association recommends measuring the rate of night flow by creating District-Metered Areas (DMAs). However, in creating DMAs, especially for the existing and old WDNs, minimizing the boundary pipes between the DMAs, leakage, cost, and stable hydraulics should be taken into account. The layout should be optimally designed regarding geometry and the optimum number. In this study, the results of two-objective algorithms have been compared in creating DMAs. NSGAII, MOGWO, SPEA2, and MOPSO algorithms are used to select the best optimization algorithm in the physical partitioning. The results showed that the SPEA2 algorithm performs better than other algorithms. By examining the creation of different DMAs by changing the number and geometry of the areas in the networks, the optimal case of the areas was calculated according to two optimization goals, as well as different indicators such as modularity and nodal pressure values.

This study presents a new method to create DMAs in the existing water distribution network with cost and leakage reduction approaches. The creation of areas with these two approaches has yet to be investigated in past studies. This method includes the phases of clustering, physical partitioning, and analysis of the results. The presented method was used on the ZJ water distribution network in China. Also, the results of the two-objective algorithms have been compared for the first time in creating DMAs.

The results showed that the standard deviation of the nodal pressure of the network has decreased by 14.8% and the nodal leakage rate of the network by 5.8% compared to the case without creating DMAs. In addition to controlling leakage in the network, the creation of DMAs has led to pressure management and leakage reduction in the water distribution network.

The presented method creates DMAs with the lowest cost and rate of leakage and pressure control in helping justice of the water distribution network. Also, the SPEA2 two-objective algorithm is suggested as the best algorithm for creating DMAs among the four reviewed algorithms.

The piano key side weir is introduced as a new hydraulic structure to improve the outflow performance where the opening length of distribution channels is restricted. This study used 370 high-resolution tests on three linear and 24 triangular piano key side weirs. The study experimentally investigates the effects of different upstream angles on the discharge coefficient of the triangular piano key side weirs with various geometries. In these tests, continuous improvement has been achieved by reducing the ratio of upstream angles for triangular piano key side weirs with the same crest length. The estimation of discharge coefficients using De Marchi’s equation shows an average increase of 7.2% to 17% for the triangular piano key side weirs, considering the variation of upstream angles. The data analysis shows that the deflection angles of triangular piano key side weirs are also vital for outflow efficiency. A new reliable equation is proposed to estimate the discharge coefficient of piano key side weirs based on some dimensionless parameters (different ratios of upstream angles (δ1/δ2), dimensionless weir length (L/W), dimensionless weir height (h1/P), dimensionless overhang length (h1/ Bi), and the downstream Froude number (F2). Also, the statistical indices were used to evaluate the precision of the nonlinear equation for triangular piano key side weirs. The R2 and MAE for 70% of the experimental data were 0.91 and 0.052, respectively.

Water supply networks are considered as critical infrastructures in urban systems, the use of which has always been associated with many challenges. In these networks, the problems such as pipe breaks, water leakages and, non-uniform distribution of nodal pressures are considered as frequent challenges. In this study, a time-based scheduling approach for the use of pressure control equipment in the water network has been presented. In this regard, two operational scenarios consisting of simultaneous use of individual pressure reducing valves in the first scenario (individual scenario) and the hybrid use of pressure reducing valves with a variable speed pump in the second scenario (hybrid scenario) have been investigated. In this case, Operational programs have been developed with the aim of achieving the benefits of pressure management based on providing minimum temporal and spatial pressure variations, using a genetic algorithm as an optimization tool. Finally, the proposed strategies based on dual scenarios were validated in the context of a theoretical network as well as a real network. The optimal scenario was determined by calculating the hydraulic evaluation indicators of the network. The results show that the simultaneous use of pressure reducing valves with a variable speed pump (hybrid scenario), has been more effective in reducing pressure variations and increasing desired pressure coverage, in comparison with the individual scenario.

The leakage is one of the main challenges in the operation of water distribution networks. In the present study, leakage location is detected using Feedforward Artificial Neural Networks (ANNs). For this purpose, two scenarios are considered for training the ANNs. In the first scenario, two simultaneous leakages with equal values, and in the second scenario, two simultaneous leakages but with unequal values are applied to every pair of network node. The training data are analyzed by EPANET2.0 hydraulic simulation software linked with the MATLAB programming language. In both scenarios, first, ANNs are trained using flow rates of total pipes number. Then, sensitivity analysis is performed by Hybrid ANNs for the flow rates of different percent of pipes number. The results of the proposed Hybrid ANNs indicate that in the first scenario, by having the flow rates of 10% of the total pipes, the locations of two simultaneous leakages are successfully determined. However, for the second scenario, while the difference between the two leakages is less than 80% of the maximum leakage (up to ratio value of 10 and 90 % leakages), by having the flow rates of 10% of the total pipes, the locations of the two leakages are still successfully determined. But for larger differences, only the location of the bigger leakage can be detected. Despite the complexities of the second scenario, the proposed ANNs could successfully detect the location of the bigger leakage.

Water supply networks are directly related to the economic and social development of urban communities. Due to the rapid increase in population and urbanization, these networks should be properly maintained and rehabilitated. In this paper, an unsupervised learning method with OPTICS density-based clustering algorithm is used to determine the priority areas for rehabilitation. 361 burst event data in one of the Mashhad water network zones were analyzed. The algorithm identified a total number of 16 clusters at 5 different levels of importance. These 16 clusters, which are considered sub-clusters for higher levels, were compared in terms of burst rate. Three clusters with failure rates of 79.1, 62.2, and 50.1 (failures/100 km/year) were introduced as the main priorities for rehabilitation and renovation, respectively. The average burst rate in the whole network was 14.8. The identified clusters were examined in terms of pipe material and diameter and their most affecting factors on the burst rate. The obtained results showed that the OPTICS clustering algorithm has a significant ability to determine priority zones for the rehabilitation plan, by identifying multiple clusters and their according levels. Therefore, the proposed method can be used as a practical and flexible tool to prioritize the rehabilitation process of water networks and identify the main causes of failure events, avoiding complex computational methods or the personal judgment of experts.

As the main component of real water losses, leakage afflicts most water networks worldwide; even the best Water Distribution Networks (WDNs) have leakage in their network infrastructure. Several methods and strategies have been developed for leakage reduction and performance improvement in WDNs. In practice, leakage control strategies, including active leakage control, passive leakage control, pressure management, and infrastructure asset management, are performed by water utilities to reduce leakage. The main question is, which of these leakage management strategies are the most appropriate for a specific WDN? The answer to this question is obtained by analyzing the economic level of leakage (ELL). In fact, the essential component of a leakage control strategy is that its target is set in terms of the economic level of leakage (ELL). This paper provides a comprehensive review of the estimation of the ELL at different time frames, including short-run, long-run, and sustainable in WDNs. In addition, a procedure to estimate the ELL is proposed according to the conditions in each network or the relevant water utilities. Results of this review could be a valuable reference resource for practitioners and researchers dealing with non-revenue water in WDNs.

Side weirs are a type of hydraulic structures that can be used as a deviator structure for controlling and dispensation of discharge in flood and high velocity flows. The flow on these structures is spatially varied flow type with decreasing discharge. Due to the applications of side weirs for transferring and controlling discharge in flood flows and considerable velocities, its very likely to have supercritical flow on these kind of structures. Piano key and labyrinth side weirs can be used, when the width of the weir opening is limited. The increase in side weir's effective length relative to its opening is one of the advantages of these side weirs. The majority of studies done on the Piano key weirs had been limited to experimental methods, due to the limited conditions of laboratory, high cost and recent development in numerical models, its important to simulate these weirs in fluid dynamics software’s. In this research side weirs with different plans have been simulated by FLOW-3D. The FLOW-3D numerical model has been calibrated and verified for simulating side weirs using experimental results. Determination and presentation of the relation between the kinetic energy correction factor () and the momentum correction factor (β), discharge coefficient for Piano key side weirs in supercritical flow and comparing the shapes of piano key side weirs are some of the results of this research. These results can be used in designing these side weirs.

One of the advantages of designing water distribution networks (WDNs) as a district metered areas (DMAs) is to identify the leakage in each area by controlling the input and output flow, which of course requires the separating areas and installation of flowmeters between the interconnect pipes of areas. Considering that the most existing WDNs have been expanded traditionally and not as DMA, turning them into DMAs would require huge costs and might not be even practical in some networks. In this paper, a theoretical idea of virtual DMA is presented to identify the leakage in each areas. The innovation of this paper is the ability to transform networks into DMAs using a combination of the graph theory and artificial neural network to find leaks without using a flowmeter. The proposed method, in addition to reducing costs for the flowmeters, also increases the speed of detection of leakage areas. In addition, there is no need to specify the number of leakage nodes before the leak operation begins. The proposed method has been applied for the Balerma WDN in Spain with 443 nodes and 454 pipes for two, three and four simultaneous leaks. The results of this paper show that the proposed theory in this method is able to detect leakage in each area, and this method can determine the number of optimal virtual DMA for each network. In all examples, the leakage area was correctly predicted and the maximum leakage error was about 6.5%.

Leaks in water supply networks cause problems such as water loss and contamination. Due to the difficulties of the current leak detection methods, some methods are recently being developed that use network field data (in the form of flow or pressure) and hydraulic simulation to determine the location of leaks. In this paper, a new method is proposed for locating the leaky areas in water supply networks, based on the results of field pressure measurements and investigating the hydraulic grade line. Suggestions on the number and arrangement of pressure meters in the network were also recommended. The obtained results for three scenarios in a looped water network with 30 junctions were presented. The results showed that this method can correctly identify the leak areas with no limitation on the number of simultaneous leaks in the network. On the other hand, this method is verifiable, unlike the most commonly leak analytical methods. In this methodology, if the number of field pressure meters increases, the reported leaky areas become smaller. As a scenario, by increasing the number of pressure meters from 3 to 4, the reported area gets halved. The proposed method can be utilized by operators of water distribution and transport networks.

Side weir has many applications in water distribution and regulation in irrigation and flood control. For a constant opening length, weir crest can be design as labyrinth or piano key shape to increase the developed length and discharge coefficient. Another way to increase the side weir efficiency is oblique design, which make the weir crest aligned with the diverted flow. Combining the two noted approach leads to design a side weir with longer developed crest length and aligned with flow which has high performance. In this study, piano key side weirs with different key angles were studied. Flow characteristic including deflection angle and streamlines and also discharge coefficient were studied. Results show that angled keys aligned with the flow direction, increases performance of the piano key side weir up to 12 percent in high Froude numbers. Oblique keys can reduce the turbulence usually occurs in symmetric piano key side weir and results in higher discharge coefficient. The results can be used to design a side weir with which applied in conditions with high Froude numbers such as flood control.

Leakage in water distribution system is a crucial issue because of problems such as water loss, water pollution, and land subsidence. Current leakage detection methods are usually costly and time-consuming, therefore new methods have been developed based on water networks simulation. In this paper, a new method for identifying the location and amount of leakage in water distribution system based on a two-step Algorithm is introduced. The first (Stepped Algorithm) and second (Firefly Algorithm) steps for determination of leak location and amount of leakage are respectively used which is applicable for even two simultaneous leaks. The proposed method is based on the comparison of the network hydraulic simulation results and some field network data (pressure or flow or their combination). The obtained results for six examples in a looped-water network are presented. The results show that the proposed algorithm is able to locate either one leak or two simultaneous leaks and their leakage values with less than 8% error. The proposed method developed in this paper can be utilized by operators of water supply networks for identifying the position and amount of leaks.

One of the most effective methods of coping with leakage in water distribution networks is pressure management. Therefore, a proper understanding of leakage behavior and its relationship with pressure variations can play a significant role in water loss control. The use of high-density polyethylene (HDPE) pipes has increased in recent years in water distribution networks so that in some rural area and small cities, these pipes have been utilized only. The aim of this study is to investigate the leakage behavior of orifices in HDPE pipes.

In the present study, the leakage behavior of polyethylene pipes has been investigated numerically and experimentally. In this study, the effect of temperature as one of the main factors on leakage behavior has been considered.

The results showed that the Torricelli's classic relationship for the orifices can be used and the amount of leakage exponent for the orifices is approximately 0.5. This study shows that the discharge coefficient of the outflow from the orifices is dependent on some parameters such as Reynolds number, the thickness of pipe wall, orifice diameter, surrounding environment and orifice deformation.

The assumption of no deformation for the orifices in HDPE pipes with increasing pressure, particularly at high temperatures, is not necessary true. The symmetry state of the orifices in low-elastic pipes is removed with the pressure increase, due to the distribution of stress at the opening and also the effect of the Poisson coefficient, thereby reducing the discharge coefficient.

Pressure management (PM) is one of the most effective methods of leakage management in water distribution networks (WDNs). In addition to reducing leakage, it provides many benefits for water utilities. The purpose of this paper is an economic analysis of the PM through a comprehensive cost-benefit analysis, taking into account the various aspects of the implementation of PM in WDNs. For this purpose, a mathematical model was developed for evaluating the benefits arising from implementing PM on the reduction of leakage, pipe breaks, active leakage control, water consumption, energy consumption, building damages and the increase of customer satisfaction and the costs of purchase, installation, operation and maintenance, and revenue reduction due to the reduction of water consumption. Using the developed model, the net benefit and benefit/cost ratio can be calculated for each PM scheme. As a case study, the advanced PM system was implemented through the installation of time modulated (TM) and flow modulated (FM) pressure reducing valves (PRVs) in a district metered area (DMA) located in Mashhad city. The net benefit and benefit/cost ration was then estimated by the developed mathematical model. The results showed that the net benefit of PM system through FM is greater than TM and the benefit/cost ratio was obtained 3.7 and 3.2 respectively. The developed mathematical model will assist water managers and practitioners in comprehensive understanding of the benefits and economic justification for implementing PM schemes.

Piano Key Weirs, a developed scheme of labyrinth weirs. In this study, 36 trapezoidal Piano Key Weirs models were conducted in 360 different geometric and hydraulic conditions. Experiments were conducted in a 11 m long flume with a rectangular cross section of 49 cm width and 70 cm height in which the effect of dimensionless ratios on the discharge coefficient was investigated. The results showed that L/W=6.54, B/P=2.33 and Wi/Wo=1.33 compared with other values ​​that have been tested in this study, increasing the discharge coefficient 113, 63 and 33 percent respectively, Therefore, they are suggested as optimal ratio for trapezoidal plan. Which is close to the ratio that other researchers have proposed for the rectangular plan. Also, by using SPSS software and taking correlation coefficient (R2) and Normalized Root Mean Square Error (NRMSE), relations was proposed to estimate the discharge coefficient and the sensitivity of the proposed relationship to its parameters showed that this relation shows the highest and lowest sensitivity to the L/W and Wi/Wo parameters respectively.

For better utilization of water distribution networks (WDNs), it is recommended that the existing networks be converted into Distinct Metered Areas (DMAs). Due to the complexity of the old networks, the conversion of these networks into DMA is a costly and sensitive issue. In this paper, a model has been developed to optimize implementation of the old networks into DMA by using the graph theory and water distribution system modeling software (EPANET), while the minimum required standard pressure is met and the number of linked pipes between the proposed areas is minimum. The minimum number of linked pipes will minimize the cost of the needed flowmeters. The developed model has been successfully applied for Poulakis WDN with 30 nodes and 50 pipes in different statuses and for the actual Bushehr WDN with about 3740 nodes and 3980 pipes. The output result shows that the developed model, in a satisfactory way, converts water distribution networks into DMAs with respect to the hydraulic constrainsts.

One of the main responsibilities of water and wastewater companies in the field of operating of water distribution networks (WDNs) is the management and control of leakage from these networks. In this regard, active leakage control (ALC) is one of the main strategies in reducing leakage and achieving economic level of leakage (ELL). In this paper, a practical methodology was developed to determine the ELL which is included the steps determining the points of pressure and flow rate measurements, collecting of required field data and cost data, the estimation of leakage level in the network and the determination of the ELL of the network based on the ALC strategy. Economic performance indicators such as the economic leakage index (ELI) and the economic network efficiency (ENE) are also obtained using the determined ELL. The developed methodology was applied for a district of the WDN of Mashhad. The results showed that the ELL in the study area is 27.5 m3/connection/year. While the current level of leakage was estimated to be around 49.2 m3/connection/year, based on the minimum night flow (MNF) analysis. Moreover, the ELI and ENE were calculated 1.79 and 56% respectively. The developed methodology in this paper can assist practitioners and managers of water and wastewater companies for target-setting of the level of leakage and determining of the ELL based on it.

Anomaly or outlier detection of flow data in water distribution networks (WDNs) is implemented in data preparation and prepossessing step to achieve reliable historical data; it is important to improve the leakage assessment and management methods and the operations of the network efficiently. The main objective of this paper is to develop a new methodology based on unsupervised learning methods for anomaly or outlier detection in a flow data set in WDNs. The developed methodology includes three steps 1- required data acquisition, 2- data validation and normalization, and 3- anomaly or outlier detection using the density-based spatial clustering of application with noise (DBSCAN) algorithm. The proposed methodology is applied for inflow data into an area in Tehran's urban water distribution network with 15-min sampling intervals for 1394. The results showed that the developed methodology is capable to the detection anomalies due to different type of pipe breaks and unusual legitimate consumption such as water usage due to changes in water consumption pattern or unauthorized consumption. Therefore, this methodology can be used as an applicable and flexible tool for monitoring flow data and detecting and eliminating of different types of outliers from them.

Leakage in water distribution networks (WDN) causes loss of water and energy resources. The amount of leakage in WDNs is influenced by pressure. Leakage prediction and optimal decision making on leakage control strategies require a deep understanding of the leakage-pressure relationship. High-density polyethylene pipes (HDPE) have been used extensively in water distribution networks in recent decades, and leakage behavior in this material is still debatable. The purpose of this study was to better understand the leakage behavior of the longitudinal slits of the high-density polyethylene pipes and the effective parameters in their elastic phase.
Material and To achieve the objectives of this research, a semi-industrial laboratory model was developed. Based on the preliminary studies and literature review, effective parameters were extracted and then 10 samples were prepared by considering the parameters of diameter and thickness of pipes, dimensions of slits, and temperature. Then, the samples were pressurized by a high-pressure pump and by setting the pressure, the leakage discharge of the longitudinal slits and also the temperature were measured for each pressure during the test. Using the dimensional analysis method, the results were analyzed. In the longitudinal slit of HDPE pipes, the leakage flow was a function of changes in the area of the leak. Our results showed that there is a relatively linear relation between the change in the effective area of the leak position and the pressure in the elastic state. Also, the rate of changes in the area relative to pressure variations depends on the parameters such as the dimensions of slits, pipe diameter and thickness, and temperature. Among these parameters, the effect of the slits’ length and the temperature had a greater effect on the amount of leakage in longitudinal slits. Using experimental results and dimensional analysis, a relationship was developed to estimate the effective area change of the leak in the longitudinal slits in the HDPE pipes. Using this relationship, leakage can be calculated at different pressures. In the present study, the leakage exponent for longitudinal slits in the HDPE pipe was calculated in the range of 0.44 to 1.44 and was consistent with the proposed relationship. In the elastic state, if any of the effective parameters such as slits’ length or pressure increased, the leakage power approached 1.5. Given the uncertainty about the size of the slits in the water distribution networks, an exact number cannot be proposed for the leakage power, but the average leakage power in our experiment was equal to one. In another experiment, the effect of temperature on leakage was investigated independently at a pressure of 5 bar and showed that an increase in temperature could increase the leakage in HDPE pipes. Also, at 40 °C, it exited from the elastic state, and the slope of the changes increased significantly. The mean value of the leakage power for the current experiment was equal to one, which corresponds to the previously reported amount that was used to estimate the leakage rate of WDNs. According to this study, a relationship was used to estimate the variation in the area of the leak in terms of the shape and material of the pipe, the shape of the slits and the temperature relative to the pressure. For the first time, the temperature parameter was also investigated in relation to the variation in the area of a slit and discharge leakage. Considering the significant effect of temperature, it is suggested a new relationship to be used in the tropics to estimate the amount of leakage.

Besides reducing leakage and consumption, pressure management affects occurrence of new bursts in water supply systems. Over the past two decades, several researchers throughout the world have studied the benefits of pressure management on reduction in the burst frequencies. During this period a wide assortment of empirical models have been developed to determine pressure-burst relationships such as pressure-leakage relationships. This paper aims to conduct a comprehensive review of these studies, relationships and empirical models pertaining to the effects of pressure management on the break rates of pipes in water supply systems. For this purpose, the developed relationships and empirical models by various researchers over the last twenty years were discussed and the advantages and disadvantages of them were summarized. Based on the review, the better understand of pressure- burst relationships could be founded and the results could be used in the analysis and evaluation of pressure management schemes in water supply systems.

Pressure management is an effective method for water demand management. For evaluation of the effects of pressure changes on leakage level of water networks, the FAVAD equation is usually used. However, in this equation, exponent of pressure parameter (N) needs to be determined. For estimation of N, either some information about the leak opening is necessary or network’s leakage level needs to be known which is very difficult to measure. On the other hand, available studies about the effects of pressure changes on water consumptions and leakage don’t seem to be enough. In the present study, a new analytical method is proposed for calculation of N, in which direct measurement of leakage level, does not need. In order to test ability of the proposed method as well as the pressure effects on leakage and water consumption, an isolated water network in Tehran city has been selected.
Different pressure patterns were implemented on outlet of a pressure reducing valve and variation of the minimum night flows, customers’ water consumption and inlet flow discharge were then measured in the pilot network. In this study, implementation of the pressure management could reduce the minimum night flow, water inflow and customer's consumption up to 50, 21 and 30 percent, respectively. Furthermore, using the obtained data, different equations for estimation of pressure effects on reducing of night flow, total inflow and water consumption are presented.
Considering water scarcity, population growth, increase of water consumption per capita and high cost of drinking water production, optimum usage of existing water resources is a vital issue. Pressure management is one of the most effective solutions among the water demand management methods to help solving these problems.
Although pressure management is one of the best methods for water demand management, some operation managers ignore using this method in their water distribution networks and would prefer to use other methods such as water rationing when they face water scarcity. It may be because of lack of experience on pressure management. The main objective of this paper is to show the good results and practicability of pressure management especially for old and existing water distribution networks.
N parameter in the FAVAD’s pressure-leakage formula, represents the power-law relationship between leakage rate and pressure. The value of the exponent N may vary from 0.5 for “Fixed Area” leaks to 1.5 or more for “Variable Area” leaks where leak area varies with pressure. In this paper a new modified method of calculation the N exponent is shown.
An isolated water distribution network in Tehran city was chosen for this study (Figure 1). Region is supplied with only one reservoir. After isolation of the region, a modulated PRV in the entrance of the isolated region was assembled, moreover, a pressure regulator were installed to induce different pressure patterns. Also an ultrasonic flowmeter was used in downstream of the reservoir to measure input flow to the isolated region.
Since at the begging of study the optimum pressure pattern was not exactly known, therefore after preparation of isolated region and setting up the equipment, different pressure patterns were applied to the modulated PRV as try and error process to find the best pattern. These patterns are shown in Figure 2. This process continued by applying more pressure reduction to the PRV until the first complaint was received from the customers. On the other hand, by having different pressure patterns and measurement of night flow for each one, it could be possible to follow changing of night flow with water pressure variation.
For each patterns inflow was recorded in 10 minute intervals and the measurements were continued for a week. Output pressure of PRV before installation of modulated PRV was 50 meters. It should be noticed that output pressure patterns of PRV were adjusted such that the costumers didn’t face any pressure shortage and no complaint was reported during the study.
Different conditions and information of measurements are shown in Table 1. For better comparison of mentioned patterns (Figure 2), average amount of applied pressure patterns during 24 hours is also mentioned in table.
After completion of measurements, the data was analysed and following results are obtained: Results show that with no complaints of consumers, total inlet flow reduced about 21 percent in final week. Inlet flow is composed of network leakage and consumer’s consumption, reduction of inlet flow means lower consumers’ consumption and/or lower network leakage.
To study the effects of pressure management on the consumers’ consumption, 64 consumers were selected as sample of total consumers and their domestic water consumptions measured by reading their flow meters in different weeks during the study period. Results for domestic water consumptions are shown in Table 2.
Results show more than 30 percent water saving for the consumers’ consumption in final week. Minimum night flow is composed of network leakage and consumer’s night consumption. Since amount of consumer’s night consumption is almost constant, the minimum night flow could be a convenient indicator for estimation of network’s leakage. Minimum night flow occurs at midnight hours and especially between 12 to 4 AM.
The trend of results shows a reduction of minimum night flow with reduction of pressure and a potential for reduction of night flow more than 30 percent. It should be also mentioned that no complaint was received from consumers when final pattern was applied to the modulated PRV. Table 3 shows the measurement results of minimum night flow in the different weeks (weeks).
In this study, using data obtained from the pilot, a novel analytical method for estimation of the pressure exponent (N) has been presented. Using this method N=1.15 was estimated for the network under study.
In present study, results of pressure management on distribution network show that with no complaints of consumers, some benefits such as leakage reduction and consumer’s consumption are practically achievable.
A novel analytical method for estimation of the pressure exponent (N) in the FAVAD equation as well as analytical equations for evaluation of pressure management’s effects on leakage and water consumption have been recommended.
Considering complexity of water networks in term of flow hydraulic, geometrical and material of pipes, more research are still needed to study the relation between pressure, leakage and consumers’ water consumption.

An objective of the Targeted Subsidy Act in Iran, which came into effect in 2010 in Iran, is to manage water demand. Despite the importance of this Act, evaluation of its effects especially on urban water networks has been rarely reported. The present study aims to investigate the impacts of the first phase of its implementation on the water consumption for different uses in the city of Mashhad. For this purpose, the data records of water consumption over a period of 10 years were analyzed and expert views were collected. Results indicated that although the Act in its early years of implementation led to reduced consumption and a shift was observed in water consumption for different uses, the increasing trend of water consumption was later resumed. It was also found that as reductions in water consumption for different urban uses is directly related to the users’ interests. Water consumption reduction fits the gamma probability density function. Based on the data obtained, water production and supply did not decline during the study period despite the reduction observed by authorized users. It may, therefore, be inferred that illegal connections increased during the study period. Thus, the Act did not seemingly have the impacts, at least as much as expected, on reducing urban water consumption.