Development of a new comprehensive framework for the evaluation of leak management components and practices

Failures and leaks occur in mains and service connections in water distribution systems (WDSs) due to various factors. Non-revenue water (NRW) is defined as water delivered to WDSs but not charged (Lambert et al. 1999). The NRW volume includes the components of the real losses, apparent losses, and unbilled authorized consumptions (Pearson 2019). Globally, annual leakage rates in WDSs are in the range of 25–30% (European Commission 2014), while the NRW rate is around 30% (Liemberger & Wyatt 2019; Berardi & Giustolisi 2021). A significant part of water resources is lost in the network due to leakages. While the leakage rate is more than 50% in developing countries around the world, this rate is between 3 and 7% in well-maintained networks in developed countries (Puust et al. 2010; Gupta & Kulat 2018; Duan et al. 2020; Moslehi et al. 2021). Moreover, according to the World Bank, nearly 48 billion m³ of water gets lost annually from WDSs, costing US $14 billion to water utilities (Mutikanga et al. 2013; Gupta & Kulat 2018). In the report published by the Turkish Water Institute (SUEN), according to the data from 25 administrations, the average NRW rate is 42%, with the lowest and highest values being 22 and 67%, respectively (SUEN 2020). In addition, the total annual economic loss due to NRW in the administrations exceeded 7 billion Turkish Liras in the year 2017 (SUEN 2017).

Trends in climate change and global warming negatively affect surface and groundwater resources in terms of quantity and quality (IPCC 2015). In systems with high leakages, more water is supplied to the systems to meet the demand, existing resources are insufficient, and as a result, new resources are sought, and access to clean water becomes increasingly difficult with excessive water consumption. Therefore, these negative effects of NRW or leakages should be minimized (Bakhtiari et al. 2020). Reducing all water loss components to zero is neither technically possible nor economically viable. The water loss components should be accurately assessed and prioritized for minimizing loss (Al-Washali et al. 2020).

In the literature, basic methods, including pressure management (PM) (Kanakoudis & Gonelas 2016; Creaco & Walski 2017; Muhammetoglu et al. 2018), district metered area (DMA) planning (Ferrari & Savic 2015; Campbell et al. 2016), active leakage control (ALC) (Berardi et al. 2015; Candelieri et al. 2015; Cabral et al. 2019; Lipiwattanakarn et al. 2019), leakage modeling (Guo et al. 2021), failure repair, and maintenance and pipe material management (Deidda et al. 2014; Marchionni et al. 2016; Agathokleous & Christodoulou 2017), have been applied for the reduction, prevention, and management of leakages. However, before applying these methods, it is important to analyze the current state of the system and the current application levels of leakage management practices, in terms of reducing the initial investment and operation–maintenance costs (Yilmaz et al. 2021a).

A detailed analysis of the current state of the network, operating conditions, and system components is the first and critical step in developing a water loss management (WLM) strategy (Liemberger & Farley 2004; Farley & Limberger 2005). In WDS data, equipment and technical capacity should be sufficient for ALC, and failure repair and maintenance and PM strategies should be applied for ensuring a sustainable WLM. The network characteristics and operating conditions should be monitored regularly in order to define the prevailing situation correctly (Vicente et al. 2016; Monsef et al. 2018; Moslehi et al. 2021). The standard water balance table, minimum night flow (MNF), and component analysis (with failure records) methods have been applied for the estimation of leaks in WDSs. The failure rates, network conditions, and field data used in these methods are highly effective in estimating leaks (Amoatey et al. 2018). Unreported leaks, which constitute a significant part of the leaks in WDSs, occur mostly at the service connections. The ALC in DMAs should be applied in order to determine and reduce these leaks in the WDSs (Boztaş et al. 2019).

Water utilities work hard to reduce water losses, but this results in high costs. To control water loss, first, the relative contribution to the loss of the various components should be identified. Next, how much would have to be spent for loss reduction in a particular component should be considered. Based on this, what kind of investment has the greatest impact in terms of the least cost should be determined (Moslehi et al. 2021; Serafeim et al. 2022). In leakage management, the most appropriate level at which leaks can be reduced should be defined to ensure water, energy, and financial efficiency. Therefore, the current state of the systems should be analyzed, the application levels of the methods should be determined, and the requirements should be defined (Yılmaz et al. 2021b). A new algorithm was proposed by Firat et al. (2021) in order to define the economic leakage level (ELL) in WDSs. In this algorithm, parameters that include the consideration of the current state of the administration (current leakage rate, personnel, and equipment) and the current application levels of methods (DMA, PM, and ALC practices) are considered as the fundamental component (Firat et al. 2021). Wu et al. (2022) proposed a comprehensive solution framework for anomaly detection and localization by integrating data-driven analytics with hydraulic model calibration. The proposed approach has been proved to be effective at analyzing the monitoring data for flow and pressure to detect anomaly.

Leaks cause water resource inefficiency, an increase in operating costs, a decrease in service quality, and an increase in customer complaints. In the literature, studies were carried out within the scope of determining and analyzing leaks according to various methods in general. However, the methods applied to manage leaks are generally time-consuming and costly. Therefore, the current state of the administration, personnel, technical, and financial capacity should be examined, and the applicability of methods and the application levels of the currently applied methods should be analyzed on the basis of measurable, appropriate, and objective criteria. Therefore, in this study, a new comprehensive framework is proposed using the scoring table to evaluate and highlight the reliability of data and to analyze the current application levels of leakage management practices in WDSs. The developed framework consists of 60 sub-components determined to cover the WLM practices. The purpose of this study is not to calculate the level of leakage or the ELL. Rather, the quality of the data used in leakage management and analysis and the application levels of the applied methods are questioned. Thus, the data quality (quite good, good, doubtful, poor, and quite poor) is classified according to the application levels of the leakage management practices. The class of the component is determined according to the examination and evaluation made in the administration. This classification is not made by the personnel in the administration. Accordingly, it will be possible to provide more accurate data for sustainable leakage management in the administration and make field applications more systematic.

Leaks are one of the most fundamental problems in transmission lines and distribution systems. Some of the leaks that occur in WDSs are openly exposed (reported leaks). However, a significant part of the failures are unreported failures (Lambert et al. 1999; Pearson 2019). Passive leak control is applied to manage reported failures, while active leak control is applied to reduce unreported leaks. The most basic methods applied to reduce leaks are PM (García-Ávila et al. 2019; Özdemir et al. 2021), DMA planning and MNF analysis (Negharchi & Shafaghat 2020; Marzola et al. 2021), failure management (Arai et al. 2010; Kahn et al. 2020), and leak detection with regional or local acoustic equipment (Giaquinto et al. 2018; Shukla & Piratla 2020). However, these methods require team, equipment, institutional and personnel experience, and financial capacity. Therefore, the prevailing situation in the administration, its technical and institutional experience, applicability, and the necessity of methods should be evaluated in detail. Moreover, the current levels of the application of the WLM methods applied in the administration should be analyzed. The methods/processes that can be applied for the effective and sustainable management of the WLM components in the administration should be determined on the basis of this analysis.

The main problems encountered in WLM can be given as follows: (i) the lack of a roadmap for data collection, monitoring, and analysis, (ii) the lack of a methodology that evaluates the application levels of leakage components in detail, (iii) the absence of a method that identifies the weaknesses/strengths and the risks based on the current situation analysis, and (iv) the lack of setting appropriate targets based on the current situation analysis. Therefore, it is important to develop a current status evaluation framework for devising an effective, sustainable (which is applicable), and a long-term WLM strategy in administration.

A sustainable strategic WLM model, which includes a current condition evaluation matrix, a data matrix, a performance evaluation system, and a method recommendation matrix, has been proposed and outlined by Bozkurt et al. (2022). In this study, a new comprehensive framework for leakage management practices was developed on the basis of the WLM model proposed by Bozkurt et al. (2022). This assessment model is directly associated with the data used in leak analysis. Thus, it is planned to define the components that lack data or methods, to make gap analysis, to define the components that need improvement, and to identify the weaknesses and strengths of the system. In this model, a total of 60 components, which are grouped as ‘Basic-Level Practices’, ‘Moderate-Level Practices’, and ‘Advanced-Level Practices’, were defined to cover leakage management (Tables 1–3). The applicability, requirements (financial, data, technological capacity, and experience), and difficulty levels of the components in the field are considered in this grouping. While the scoring results in the administration are evaluated separately for these levels, a general evaluation is made for the whole matrix at the same time. The aim here is to reveal the current state of the administration at each implementation level. Thus, information that will form a reference in determining the priority sub-components in improvement will be produced.

The leakage components are scored between 0 and 5 (0 point (quite poor), 1 point (poor), 2 points (insufficient), 3 points (moderate), 4 points (good), and 5 points (quite good)) in the developed framework. Components with 0 and 1 points constitute weakness in leakage management (if data quality is poor, the components should be improved). The priority target for these components is determined as 3 points (moderate level), then 4 points (good level), and finally 5 points (quite good level). Similarly, components with 2 and 3 points constitute weakness in leakage management (if data quality is questionable, it needs improvement); however, they could be used in analysis. For these components, the priority target is 4 points (good level) and then 5 points (quite good level). On the other hand, if a component has a score of 4 (good data quality) or 5 (if data quality is very good, the current status should be kept), this component constitutes the strength of the administration. The final target for components with a current score of 4 were defined as 5 (quite good level) based on technical and economic criteria. Components with a current score of 5 are evaluated as ‘existing conditions should be kept’.

The framework proposed in this study was tested with real field data in pilot administrations. For this, the Bursa Water Administration (Administration 1), the Kayseri Water Administration (Administration 2), and the Denizli Water Administration (Administration 3) in Turkey were chosen as study areas (Figure 1). Administration 1, located in the west of Turkey, has a surface area of 10,820 km². This administration has a network main line length of approximately 7,100 km. The water requirement of the administration is met from surface and underground water resources. Administration 2, located in the west of Turkey, has a surface area of 12,321 km². This administration has a network main line length of approximately 3,000 km. The water requirement of the administration is met from surface and underground water resources. Administration 3, located in central Anatolia in Turkey, has a surface area of 17,000 km². This administration has a network main line length of approximately 8,000 km. The water requirement of the administration is met from underground water resources.

An on-site examination and scoring was made on the basis of the scoring tables for each variable in accordance with the situation prevailing in the administration. These components are not scored by the administration's technical staff or decision makers. In order to define the current state of the administration, each administration was visited separately by the authors (expert team in this article) at different times in 2021. In this context, all practices in the administration were evaluated in units, namely, the Drinking Water Management Department, the SCADA Department, the GIS Department, and the Information Technology Department. The activities and reports of the departments were examined to evaluate the quality of the practices for the determination of leakage components in the field. In addition, the quality of the system's basic data was evaluated by the queries made in the SCADA, GIS, and Information Technology Departments.

The score results and targets for basic-level practices in administrations are evaluated separately (Table 4). Gradual targets were defined by considering the current scores of the components in the basic-level practices (Table 4). If the current scores of the variable are 0 and 1, the primary target for these components is defined as a moderate-level target (Target I). Then, the targets defined for this variable are a good-level target (Target II) and a very good-level target (Target III), respectively. If the current scores of the variable are 2 and 3, the primary target for these components is defined as a good-level target (Target II). Then, the target defined for this variable is quite a good-level target (Target III). If the current score of the variable is 4, the primary target for these components is defined as quite a good-level target (Target III). If the current score of the variable is 5 (quite good level), it would be appropriate to keep the current situation as such. Thus, appropriate and realistic targets were determined in the administration according to the current conditions.

Network length and the number of service connections are the most basic data used in leakage management. Therefore, these data should be collected systematically. These components should be at least four points (good level) for ensuring an accurate and reliable leakage analysis. In pilot administrations, these components are generally at good or quite good level (ID2 is at the average level in Administration 2). The quality of the most basic data is at good level. Valves play quite an important role in shutting off the water in case of failure in the WDS, creating the network operation plan and applying DMAs on site. While the valve component is at a good level in Administrations 1 and 3, it is moderate in Administration 2, where this component should be improved and updated systematically.

SCADA and other information systems are important in monitoring hydraulic data in WDSs. In particular, hydraulic parameters should be monitored regularly for monitoring the water produced and supplied to the system, establishing the water budget, the analysis of MNF, the flow-pressure analysis, and WLM indicators. Information systems planning is at a good level in Administrations 1 and 2 and at an insufficient level in Administration 3. The water production SCADA component is at quite good level in all three administrations, and all resources are monitored regularly. The component of monitoring hydraulic data with SCADA in DMAs is at quite good level in Administration 2 and at moderate level in Administrations 1 and 3.

The GIS database (ID7) should be up-to-date in order to effectively manage all assets and to implement leak prevention and control strategies efficiently. Moreover, the regular Customer Relationship Management (CRM) component (ID8) in the administration should be at good level in order to systematically and quickly manage and repair the reported faults and to manage calls more systematically. These components are at quite good level in all three administrations in terms of effective management of faults and calls and the efficient implementation of leak prevention and control methods.

Leakage volume decreases in WDSs depending on the level of application of the leakage reduction and prevention method. Therefore, such methods should be applied correctly and systematically. The current application levels of components, ID11 (ALC), ID12 (DMA planning), ID13 (MNF analysis), ID14 (fault repair speed and time), and ID15 (water balance analysis), are questioned for systematic measurement and monitoring of leakages. These components are at good and/or quite good level in Administration 1, at good level in Administration 2 (ID12 and ID13 components are at moderate level), and at good level in Administration 3 (ID11 and D15 components are at moderate level). Accordingly, it is understood that an awareness for leak management practices in administrations is formed, and field applications for basic methods are at good level.

Leakage management methods are generally time-consuming and costly. Therefore, it is necessary to monitor the benefits from the methods and analyze the performances, the costs, and system operating efficiency. In the developed system, the components of ID16 (performance monitoring system), ID17 (monitoring of GIS update activities), ID18 (performance analysis and monitoring in DMAs), ID19 (fault repair costs), and ID20 (network operating efficiency monitoring) were defined and evaluated.

The components ID15, ID16, and ID17 are at good level in Administrations 1 and 2 and at moderate level in Administration 3. However, ID18, ID19, and ID20 components are generally at insufficient level in three administrations. Accordingly, these components should be applied more effectively in order to analyze and improve system operating efficiency in administrations.

In basic-level practices, the average scores of the components were calculated as 4.05 in Administration 1, 4.00 in Administration 2, and 3.30 in Administration 3. Accordingly, Administrations 1 and 2 are generally at good level in basic-level practices, while Administration 3 is at moderate level. In Administration 1, the components of ID6, ID18, ID19, and ID20 (performance monitoring and cost analysis) constitute the weakness of the administration and need improvement. In Administration 2, components ID3, ID13, ID18, ID19, and ID20 (performance monitoring and cost analysis) constitute the weakness of the administration and need improvement. In Administration 3, components ID2, ID4, ID6, ID9, ID11, ID15, ID16, ID17, ID18, ID19, and ID20 (data monitoring, performance evaluation, and cost analysis) should be improved.

The quality of basic data based on the measurement frequency, monitoring and database was evaluated within the scope of leakage management in the administrations. According to the scoring results, it was determined that the basic data measurement, monitoring, and storage components are at good level in three administrations and that the capacity and experience of the administrations are sufficient in this context. These basic data form the basis for the correct implementation of leakage prevention and reduction practices. Accordingly, it can be interpreted that the data situation required for detailed analysis and evaluation within the scope of leakage management in administrations is at good level. Similarly, the most basic leak management practices are generally at good level depending on good data quality in administrations. It is thought that the institutional and personnel experience are sufficient for the most basic practices in administrations. On the other hand, it was determined that the performance evaluation and monitoring components for the leakage components in the administrations are at moderate and/or insufficient level. These components create weaknesses in leak management and, therefore, they need to be improved as a priority.

The score results and targets for moderate-level practices in administrations are evaluated separately (Table 5).

The operating pressure (ID21) is the most basic operating data considered in leak management. Pressure should be measured regularly in order to monitor the changes in failures/leaks due to the pressure, to decide PM, and to define the most appropriate pressure level. This component is at good level in Administrations 1 and 2 and at insufficient level in Administration 3. A roadmap for WLM (ID22) is quite important for effective planning and implementation of WLM processes according to a specific flow in the field. This component is at good level in Administration 1 and at moderate level in Administrations 2 and 3.

Regular monitoring and systematic maintenance of the network are required in order to reduce operating costs. In this context, ID23 and ID26 components question maintenance and repair practices in the administration. Field works for these components in three administrations are at insufficient or poor level. A fault management system integrated with GIS (ID24) makes a significant contribution to more effective management of faults and the determination of factors. Moreover, the SCADA reservoir monitoring system (ID25) is useful for technical personnel in network operation and monitoring demand flow. These components are at good level in general.

Leaks in the WDSs and reservoirs should be identified and monitored on the basis of site inspections for ensuring an accurate leak analysis. In this context, the ID27 and ID28 components question the inspection of leaks in the distribution system and reservoirs. Moreover, the application levels of ID31, ID32, and ID33 components are highly effective in reducing leaks. The application of these components are at average level in the three administrations. The ID35 component (leakage performance monitoring) and the ID36 component (PM monitoring) are at good level in Administration 2 and at moderate level in Administrations 1 and 3. The components of ID38 and ID39 (the performance monitoring of MNF and leak detection practices) are at moderate level in Administrations 1 and 3 and at good level in Administration 2. Accordingly, performance analysis and monitoring practices are generally at good level in Administration 2.

Operation and production costs vary depending on the volume of leakage. Moreover, failure repairs cause significant annual costs. Therefore, these cost components should be analyzed with field data in order to analyze the system efficiency. The ID39 and ID40 components are at good and moderate levels in Administrations 1 and 2. The application level of these components in Administration 3 is at insufficient level.

In moderate-level practices, the average scores of the components were calculated as 3.25 in Administration 1, 3.55 in Administration 2, and 3.15 in Administration 3. Accordingly, while Administrations 1 and 3 are at moderate level, Administration 2 is at upper-moderate level. In this group, the components of maintenance and repair, cost analysis, and leak control are at moderate level in administrations and need to be improved.

The data, experience, equipment, and financial requirements of components in moderate-level applications are higher than in basic-level methods. Therefore, the application levels of the components in this group were obtained at lower level. In particular, it was determined that the scores of the failure maintenance, repair, and monitoring programs applications vary in general. On the other hand, it is seen that the practices to reduce and prevent leaks are at average level. It is thought that these methods have the potential to be applied more effectively and systematically in administrations by considering the requirements of these practices. Moreover, it was determined that the components of monitoring the performance of the most basic leak management practices are generally close to the average and/or good levels. Since the application level of the most basic methods is at good level in administrations, it is understood that the capacity and experience related to the performance monitoring is formed. The gradual target was defined by considering the current scores of the components (Table 5).

The score results and targets for advanced-level practices in administrations are evaluated separately (Table 6).

The ID41 (total service connection length on private property) component is particularly important for identifying and monitoring illegal uses or leaks on private property. This component is at good level in Administrations 1 and 2 and at moderate level in Administration 3. Leak inspection (ID44) in service connections on private property is at poor level in Administrations 1 and 3 and at quite good level in Administration 2.

The reported failures data (ID43) are required for water balance with component analysis and operating cost and leakage density analysis. A systematic analysis and monitoring of leak components requires the integration of data monitoring and management systems (ID45). Therefore, these components were considered and tested. These components are at good level in all administrations.

Leak detection equipment such as ground microphones, regional recorders, and correlators are applied to detect unreported leaks. The components of the hydraulic model (ID46), real-time system monitoring (ID47), hydraulic model–based leak detection (ID48), and leak detection with a local correlator/logger (ID49) are evaluated. The ID46 component is at good level in Administration 1 and at insufficient level in other administrations.

Leakage volume could be calculated with the bottom-up (MNF analysis) method (ID53) and component analysis (ID54) on the basis of field data, as well as top-down water balance. In administrations, the ID53 and ID54 components are generally at good level. Finally, the costs of field practices in WLM should be determined in order to check efficiency. Therefore, the cost components of ID57, ID58, ID59, and ID60 were evaluated in the three administrations. These components are generally at insufficient level in Administration 1, at good level in Administration 2, and at moderate level in Administration 3.

The average scores of the components in advanced-level practices were calculated as 2.70 in Administration 1, 3.35 in Administration 2, and 2.80 in Administration 3. Accordingly, Administrations 1 and 3 are generally at below moderate or insufficient level, and Administration 2 is above moderate or close to good level.

Field implementation and monitoring of components in advanced applications requires more data, equipment, and experience. Therefore, the scores of the components in this group are generally lower than the basic- and moderate-level practices. In this group, it was determined that especially the regional monitoring and detection of leaks had low scores. The equipment and economic capacity of the administrations need to be improved for the implementation of these components. On the other hand, since the most basic leak detection and prevention methods are applied at good level in administrations, leak estimation methods are also applied effectively according to the data obtained from these applications. However, more work should be done to make more effective cost–benefit analyses of the methods applied, especially for leakage prevention methods.

As a result, the general achievements obtained in this study can be given as follows: (i) the current application levels of leak management components in administrations are scored according to the dynamic structure of the administration, (ii) the weaknesses and strengths are defined in the scope of leakage management, and the components that need improvement are determined dynamically, (iii) realistic and appropriate targets are defined gradually (such as moderate, good, and quite good targets) on the basis of current scores on a component basis, and (iv) this model creates a roadmap in leak management, especially for decision makers and technical personnel, and serves as a reference in terms of ensuring efficiency.

In this study, a new framework has been developed to analyze and evaluate the current application levels of leakage management components in WDSs. The developed framework was tested in pilot administrations according to real field data. In basic-level practices, the average scores were calculated for Administration 1 (4.05), Administration 2 (4.00), and Administration 3 (3.30). Accordingly, Administrations 1 and 2 are generally at good level, while Administration 3 is at moderate level. It was determined that the basic data measurement, monitoring, and storage components are at good level in three administrations and that the capacity and experience of the administrations are sufficient in this context. It can be interpreted that the data situation required for detailed analysis and evaluation within the scope of leakage management in administrations is at good level. Similarly, basic leak management practices are generally at good level depending on good data quality in administrations. It is thought that the institutional and personnel experience is sufficient for the most basic practices in administrations. On the other hand, it was determined that the performance evaluation and monitoring components for the leakage components in the administrations are at moderate and/or insufficient level.

The average scores of the components in moderate practices were calculated as (3.25) for Administration 1, (3.55) for Administration 2, and (3.15) for Administration 3. Accordingly, Administrations 1 and 3 are generally at moderate level, while Administration 2 is close to good level. The data, experience, equipment, and financial requirements of components in moderate-level applications are higher than in basic-level methods. Therefore, the application levels of the components in this group were obtained at lower level. In particular, the leakage reduction and prevention practices are at average level. It is thought that these methods have the potential to be applied more effectively and systematically in administrations by considering the requirements of these practices. Moreover, since the application level of the most basic methods was at good level in the administrations, it was understood that the capacity and experience related to the performance monitoring is formed.

The average scores of the components in advanced practices were calculated as (2.70) for Administration 1, (3.35) for Administration 2, and (2.80) for Administration 3. Accordingly, Administrations 1 and 3 are generally at insufficient level and Administration 2 is close to good level. Field implementation and monitoring of components in advanced applications requires more data, equipment, and experience. Therefore, the scores of the components in this group are generally lower than the basic- and moderate-level practices. In this group, especially the regional monitoring and the detection of leaks had low scores. On the other hand, since the most basic leak detection and prevention methods are applied at good level in the administrations, leak estimation methods are also applied effectively according to the data obtained from these applications. However, more work should be done to make more effective cost–benefit analyses of the methods applied, especially for leakage prevention methods.

As a result, based on the scoring and evaluations, the proposed framework reveals the current situation according to the dynamic structure of the administration. Achievable targets and road maps are defined for each component by considering the available scores depending on this dynamic structure. It is thought that the framework developed will be a reference for the decision-making and technical personnel in the administrations, especially for defining the current situation in WLM and creating a roadmap.

This study was produced from the PhD thesis conducted by C.B.. The authors thank Inonu University, Scientific Research Project Funding for their financial support (FDK-2020/2262). This research was supported by TUBITAK (the Turkish National Science Foundation) under Project Number 220M091.

All relevant data are included in the paper or its Supplementary Information.