A hybrid knowledge-based method for pipe renewal planning in Water Distribution Systems with limited data: Application to Iran

Depósito de Investigación de la Universidad de Sevilla https://idus.us.es/ This is an Accepted Manuscript of an article published by Elsevier In Utilities Policy, Vol. 78, on October 2022, , available at: https://doi.org/10.1016/j.jup.2022.101407 Copyright 2022 Elsevier. En idUS Licencia Creative Commons CC BY-NC-ND CORRECTED PROOF Utilities Policy xxx (xxxx) 101407 Contents lists available at ScienceDirect Utilities Policy journal homepage: www.elsevier.com/locate/jup A hybrid knowledge-based method for pipe renewal planning in Water Distribution Systems with limited data: Application to Iran Sattar Salehia,*, Alicia Robles-Velascob, Ali Seyedzadehc, Aliakbar Ghazalic, Mohsen Davoudisereshtc aDepartment of Civil Engineering, Garmsar Branch, Islamic Azad University, Garmsar, Iran bDepartment of Industrial Organization and Business Management II, University of Seville, Seville, Spain cOffice of Demand Management, Customer Service and Water Loss Reduction, National Water and Wastewater Engineering Company, Tehran, Iran ARTICLE INFO Keywords: Water distribution system Renewal planning Negotiation and group decision ABSTRACT This study uses a hybrid knowledge-based method for pipe renewal planning in Water Distribution Systems (WDSs), which is useful when data are limited. The method is applied to eight Iranian WDSs to demonstrate its effectiveness. An evolutionary systems design negotiation method was used to identify planning criteria for pipe renewal by a 17-member team of expert planners. A group of 48 experienced system operators then ranked the criteria by a nominal group technique. The results indicate when accurate operational data are limited, it is possible to use the combined expertise of knowledgeable planners and experienced operators for planning pipe renewal. Abbreviations ESD Evolutionary Systems Design E-negotiations Electronic-negotiations NGT Nominal Group Technique WDS Water Distribution System 1. Introduction Among the main activities in water and sewerage companies is the renewal of Water Distribution System (WDS) assets such as pipes (Adeoti and Fati, 2020;Cabral et al., 2019;Di Nardo et al., 2018). Since pipes are one of the main components of WDSs, the design of a proper renewal plan for these assets has considerable importance (Li et al., 2016;Yoo et al., 2014;Morrison et al., 2013). For this purpose, numerous studies have been conducted in the last decade for rehabilitation planning of the WDSs; and this planning has been assessed from different viewpoints (Salehi and Fontana, 2022;Robles-Velasco et al., 2021; Elshaboury et al., 2020a;Bałut et al., 2019;Dini and Tabesh, 2019; Salehi et al., 2018a;Așchilean and Giurca, 2018;Salehi, 2017;Zayed and Mohamed, 2013;Tabesh and Saber, 2012;Saldarriaga et al., 2010). In this approach, the water pipelines are ranked for renewal works, and then the strategies for these works are identified (Kızılöz et al., 2022; Salehi et al., 2021;Moslehi et al., 2020). In most studies, the renewal of the WDSs has been mainly considered a decision-making problem (Salehi et al., 2022;Tabesh et al., 2020b;Gül and Firat, 2020;Phan et al., 2019;Minaei et al., 2019; Winkler et al., 2018;Salehi et al., 2018a;Choi et al., 2015;Scholten et al., 2014;Trojan and Morais, 2012). In the development of a decisionmaking problem, one or more people participate in solving a problem based on identified criteria; and finally, they offer alternatives as solutions to achieve specific goals. Decision-making problems can be mainly divided into individual or group decisions and, further, based on a single criterion or multiple criteria (Zolghadr-Asli et al., 2021;Kilgour and Eden, 2010). In renewal planning for WDS pipes, it is essential to consider many criteria that may include technical, operational, economic, urban, social, and security variables (Dell’Aira et al., 2021;Salehi et al., 2021; Tabesh et al., 2020b;Tabesh et al., 2020a;Cabral et al., 2019;Abd Rahman et al., 2018;Tscheikner-Gratl et al., 2016). Hence, most of the studies conducted in this field are based on multi-criteria decisionmaking methods (Gül and Firat, 2020;Salehi et al., 2018a;Tscheikner- *Corresponding author. , " style="border-top-width:0px; border-bottom-width:0px; border-left-width:0px; border-right-width:0px; padding-top:0px; padding-bottom:0px; padding-left:0px; padding-right:0px; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; display:inline; line-height:12.8px; vertical-align:baseline; fontsize:9.6px; position:relative; font-style:normal; font-weight:400; text-transform:none; font-variant:none; text-indent:0px;">[email protected], sattar.saleh [email protected] (S. Salehi), [email protected] (A. Robles-Velasco), [email protected] (A. Seyedzadeh), E-mail addresses: [email protected], [email protected] [email protected] (A. Ghazali), [email protected] (M. Davoudiseresht). https://doi.org/10.1016/j.jup.2022.101407 Received 13 March 2022; Received in revised form 21 July 2022; Accepted 21 July 2022 0957-1787/© 20XX Note: Low-resolution images were used to create this PDF. The original images will be used in the final composition. CORRECTED PROOF S. Salehi et al. Utilities Policy xxx (xxxx) 101407 Gratl et al., 2017;Lück and Nyga, 2017;Rahmani et al., 2015;Scholten et al., 2014;Salehi et al., 2018b;Zarghami et al., 2008). However, the data related to these criteria are unavailable in many WDSs, limiting the development of data-based methods for planning pipe renewal. Therefore, using knowledge-based decision-making methods based on groups of experts could be helpful in these systems. In addition, the costs related to the renewal works are significantly high. Consequently, decisions about these works cannot be made individually and must necessarily be undertaken by groups (Salehi and Fontana, 2022;Tabesh et al., 2020b;Fontana and Morais, 2017;Morais et al., 2014;Trojan and Morais, 2012;Roozbahani et al., 2012;Morais and de Almeida, 2007). Thus, it can be acknowledged that the decision-making in the field of WDS renewal is preferred to be understood as a group decisionmaking problem. Nevertheless, and according to the existing literature, only a few studies have assessed the group decision-making in this field (Salehi et al., 2021;Tabesh et al., 2020b;Salehi et al., 2018a;Trojan and Morais, 2012;Morais and Almeida, 2010;Morais and de Almeida, 2007). Salehi et al. (2021) presented a multi-criteria group decisionmaking model based on risk components called the RC-WDSR model (Risk Component-based Water Distribution Systems Renewal) to develop a strategy for WDS pipe renewal. In this model, the risk components (probability/consequence) were used independently, and the strategy for pipe renewal was identified. Their study used Fuzzy TOPSIS as multi-criteria decision model. However, group decision-making was only used to determine the weight of existing criteria, and the criteria affecting the renewal of pipes were not specified. Gül and Firat (2020) investigated the prioritization of the different WDS areas for renewal. In their study, ELECTRE I and PROMETHEE II were used as multi-criteria decision models. Additionally, the ENTROPY method, a commonly used weighting method to measure the dispersion of criteria value in decision-making and determining the criteria weights, was used to determine the coefficients of decision criteria. However, this study did not consider the use of group decision-making. Phan et al. (2019) developed a risk-based decision model to prioritize the maintenance operations of the WDS pipes. In this research, a fuzzy inference system (FIS) and an algebraic connection method were used to analyse the risk of water system pipes. However, in this study, the decision-making criteria were limited, and the developed model was not group-based. Salehi et al. (2018b) presented a multi-criteria decision model based on hybrid risk for planning the rehabilitation of water system pipes. The method proposed in this work was based on design parameters, but the research does not consider group decisionmaking. Fontana and Morais (2017) focused their study on the zoning of WDSs to implement maintenance operations. This study developed a multi-criteria group decision model to consider costs, benefits, and a group approach in the system zoning process. However, in this study, the renewal planning of pipes was not considered. Trojan and Morais (2015) presented a decision model for planning maintenance activities of WDSs. In this work, the systems were divided into three areas of correction, prevention and prediction based on the need for maintenance activities. The multi-criteria decision method used in this research was the ELECTRE II model. In addition, the group decision-making has been considered in this work which has been implemented on one of the WDSs in Brazil. However, this study did not consider identifying planning criteria for pipe renewal. Morais et al. (2014) investigated one of the WDSs in Brazil in their research. This study proposed a multi-criteria prioritization model to reduce water loss. For this purpose, the SMAA-TRI method was used to implement group decision-making. This method is based on Stochastic Multi-Criteria Acceptability Analysis (SMAA), and it allows ELECTRE TRI to be used with imprecise, arbitrarily distributed values for weights and the lambda cutting level (Figueira et al., 2004). However, in this study, the renewal of WDS pipes was not explicitly considered. Mutikanga et al. (2011) presented a multi-criteria decision model for strategic planning of water loss management in Kampala, using the PROMETHEE II method. In this research, the group decision-making method has also been used, but the rehabilitation of WDS pipes was not faced. Meanwhile, Morais and Almeida (2010) specifically assessed how to implement a group decision model for planning the renewal of WDS. Nevertheless, in this study, the planning criteria for pipe renewal were not improved. Considering the studies conducted in the field of group decisionmaking for planning the renewal of WDSs, it is evident that using the knowledge-based methods for pipe renewal is under-researched; nevertheless, experts' knowledge and experience could aid decision-making in this area. These methods could be especially useful in WDSs whose available data is limited. Therefore, the shortcoming related to this field is improved in this research. Moreover, the water distribution and sanitation industries have recently started automating data collection from their systems. In this regard, most available data are structural or physical variables, as seen in the literature review developed by Robles-Velasco et al. (2020). However, other relevant aspects such as operational or external factors are less common because they are difficult to record. In this study, we try to overcome this weakness by using planners' knowledge-based criteria and system operators’informed opinions to optimize the decisions on pipe renewal plans. For this purpose, an extensive expert team from Iran has participated in this research. In this regard, experts’knowledge and experience is used to identify planning criteria for renewing pipes in WDS. For this purpose, a hybrid method of electronic negotiations and group decision-making is proposed. Eight systems in Iran are investigated to assess this method. First, planning criteria for pipe renewal are identified by conducting electronic negotiations between 17 planners. These negotiations are held using the Evolutionary Systems Design (ESD) method. Based on the collective knowledge of 48 local water system operators, the criteria identified in the previous stage are then ranked. The method used in this stage is based on the Nominal Group Technique (NGT). 2. Methodology In general, there are various planning criteria for pipe renewal in Water Distribution Systems (WDSs). These criteria could be different in each WDS based on the purposes of renewal works; and thus, include many variables such as technical, operational, economic, urban, social, and security factors. However, the availability of these criteria could be limited, which leads to reducing the accuracy of results of data-based methods for pipe renewal. In this regard, using methods that do not require these data and instead rely on the expert knowledge and experience could be helpful for pipe renewal in distribution systems where operational data are limited. This study's objective is to identify planning criteria for pipe renewal based on a hybrid knowledge-based method in which the results are obtained from the viewpoints of experienced experts. In the proposed method, pipe renewal planning criteria are not obtained from the data-based methods but rather from the deep experience of experts who have been engaged with the water systems for many years. In the present research, the use of a hybrid method including planners' negotiations and knowledge-based group decision-making by system operators is proposed. In order to improve the validation of the results of the proposed method, this is considered a hybrid technique. Accordingly, this method includes two main steps. First, the planning criteria for pipe renewal are identified by negotiations between planners with sufficient knowledge in the related field (e.g. experts of water companies and academic professors). Then, in the second step, other operators who are faced with WDSs should rank these criteria. Since the renewal of WDSs in various regions is based on different purposes, us- 2 CORRECTED PROOF S. Salehi et al. Utilities Policy xxx (xxxx) 101407 ing the second step is vital for the proposed method. Indeed, this step ensures that pipe renewal planning is based on the local concerns of each WDS. The case study considered in this research consists of eight WDSs in Iran. However, this research could be reproducible in different countries by using the proposed method. The general stages of the method proposed in this work and related case studies are shown in Fig. 1. As shown in Fig. 1, this study is based on four steps which are described separately below: Step 1. Selecting a team of planners In the first step of this research, a 17-member team of Iranian planners was selected. This selection has been conducted by the Iran (National) Water and Sewerage Engineering Company. The planners were identified based on their experiences and knowledge in the maintenance and rehabilitation of WDSs in the different provinces of Iran. Within the group are five experts with doctoral degrees and eight with master's degrees. The other members of the group had bachelor's degrees. As we consider practical knowledge very relevant in pipe renewal, 82% of the group, i.e., 14 experts, worked at WDS companies. A more theoretical viewpoint was also introduced by including three academic professors and engineers working at Iranian consulting companies, all experts on the topic. The degree and years of experience of the selected planners and their areas of expertise are presented in Table 1. However, it should be mentioned that since all of them had high knowledge of the issue, it was assumed to give the same value to all their comments. Thus, they were not weighted based on their profiles. Step 2. Planners' negotiation using Evolutionary System Design (ESD) Method The main part of this research is the second step. In this step, several sessions of negotiations were held electronically between the 17- member planner team. These Electronic-negotiations (E-negotiations) aimed to identify planning criteria for pipe renewal. The application used for this purpose was called “Skype for Business”. These negotiations were conducted following the Evolutionary Systems Design (ESD) method. The ESD is a well-known method in the field of conducting negotiations. In this method, a general structure can be designed to define and resolve a specific problem using the alternatives suggested in the negotiations (Kilgour and Eden, 2010). Indeed, this method defines a system by assessing different configurations of its elements' relationships. In this research, the objective of renewal works of water pipelines was considered the main structure of planners' negotiations; then, the variables for achieving this objective were assessed. In the ESD method, two hierarchical techniques are considered to investigate the relations of the elements, named types 1 and 2 (Kilgour and Eden, 2010). In general, the hierarchical method of ESD type 1 is used if the relations among the elements of a problem are clear. This type of ESD method was used in this research. The steps of the hierarchical method of type 1 are included as follows (Kilgour and Eden, 2010): 1. The main objectives (values) of the problem are identified; 2. By investigating the relationship between the objectives and the related variables, the goal criteria are identified; 3. Finally, the control sub-criteria are identified by assessing the relationship between the goal criteria and the variables affecting these criteria. As a result of the ESD-based E-negotiations (electronic negotiations conducted using the ESD method), the main objective, the goal criteria Fig. 1. The Steps of the present research and related case study. 3 CORRECTED PROOF S. Salehi et al. Utilities Policy xxx (xxxx) 101407 Table 1 The degrees and years' experience of the planners selected in this research. No. Expertise Degree Years' Experience 1 Civil Engineering - Seismic Engineering Ph.D 22 2 Civil Engineering - Hydraulic Ph.D 15 3 Civil Engineering - Water Engineering Ph.D 10 4 Civil Engineering - Water Engineering Ph.D 8 5 Civil Engineering - Water and Wastewater Engineering Ph.D 5 6 Civil Engineering - Geotechnics Master 20 7 Civil Engineering - Water Quality Master 18 8 Civil Engineering - Water Distribution Systems Master 16 9 Civil Engineering - Water Distribution Systems Master 12 10 Civil Engineering - Water Engineering Master 12 11 Civil Engineering - Environmental Engineering Master 10 12 Civil Engineering - Water Quality Master 10 13 Civil Engineering - Water Distribution Systems Master 6 14 Civil Engineering Bachelor 20 15 Civil Engineering Bachelor 18 16 Civil Engineering Bachelor 15 17 Civil Engineering Bachelor 14 Fig. 2. Hierarchy 1 of the ESD system used in electronic negotiation of this research. and the control sub-criteria regarding the WDS pipe renewal plan were obtained. Fig. 2 shows the hierarchical method of type 1 of the ESD system used in this research. Step 3. Selecting a team of system operators In the third step of this study, eight provinces of Iran have been selected as case studies. A total of 48 operators, six of them belonging to each province, have assessed the importance of the goal criteria and the control sub-criteria, which were obtained as a result of the previous step. In order to have a better representation of the WDSs reality, system operators were selected from different organizational levels and with different education and work experiences. Hence, no weighting was considered for processing the information obtained from these operators. In this research, 37.5% and 52.1% of the selected system operators had bachelor's and master's degrees, respectively. Moreover, 10.4% of these operators had doctorate degrees. The years of experience of these operators were divided into three categories: less than ten years, between 10 and 20 years, and more than 20 years. In this regard, 14.6% were settled in the first category, whereas the other two categories were 54.2% and 31.2% of the system operators. The operators' profiles according to their province are presented in Table 2. Step 4. Ranking the criteria based on knowledge of operators The last step in this research is ranking the criteria based on the collective knowledge of the system operators. This ranking was conducted using the Nominal Group Technique (NGT). The NGT is one of the best methods of group decision-making for problems that need to be assessed in detail, considering criteria and alternatives. In this method, each operator evaluates the criteria separately, and finally, the ranks obtained by all the operators are added together (Lu et al., 2007). The advantage of this method is that each operator can decide independently, and the influence of operators’opinions on each other is minimized. The steps of this method are listed below (Lu et al., 2007): 1) Defining the problem statement clearly; 2) Generating a list of criteria and providing it to the operators; and 3) Finalizing and recording the ranks obtained by each operator. In general, using questionnaire forms is common in the NGT. The form used in this study is shown in Fig. 3. This study used instant messaging to provide each operator with questionnaire forms. These forms were presented as Microsoft Office tables for the operators, who also sent the forms back after their completion. It should be mentioned that the instant messaging method is one of the well-known and approved methods in Internet group decisionmaking, in which decision-makers' viewpoints are assessed using instant messaging applications (not email) (Kilgour and Eden, 2010). Table 2 The profile of the system operators in this research. No. Water and Sewerage Company of Province Number of system operators Degree (%) Years' Experience (%) Bachelor Master Ph.D. Year<10 10<Year<20 Year>20 1 Fars - Shiraz 6 83.3 16.7 0 16.7 66.6 16.7 2 Isfahan 6 16.7 83.3 0 66.6 16.7 16.7 3 Khuzestan 6 16.7 66.6 16.7 0 33.3 66.7 4 Razavi Khorasan - Mashhad 6 50 33.3 16.7 0 83.3 16.7 5 Sistan and Baluchestan 6 33.3 66.7 0 16.7 50 33.3 6 Tehran (Central + Province) 6 0 50 50 0 83.3 16.7 7 West Azerbaijan 6 50 50 0 0 50 50 8 Zanjan 6 50 50 0 16.7 50 33.3 Total (Average) 48 37.5 52.1 10.4 14.6 54.2 31.2 4 CORRECTED PROOF S. Salehi et al. Utilities Policy xxx (xxxx) 101407 Fig. 3. The NGT questionnaire form used in this study. In the NGT questionnaire form used in this study, Linguistic Values (LVs) with a seven standard range (very low, low, relatively low, medium, relatively high, high, and very high) (Salehi et al., 2018a, 2018b,2019,2021) were used to rank the importance of criteria for pipe renewal (Fig. 3). Moreover, to determine the numerical value of the importance of each criterion, a number from 1 (lowest importance) to 10 (highest importance) with equal intervals of 1.5 units was associated with each linguistic value using the bipolar scale (Figueira et al., 2005). The final importance of each criterion was identified using Formula (1). (1) c = 1-1, 1–2, …, 3-9 Wci = The number of operators who assign the ith linguistic value to the cth criterion NVi= The numerical value associated with the ith linguistic value WT= The number of total operators in each province of Iran Using this formula, the importance of goal criteria, as well as control sub-criteria, is identified by combining the viewpoints of all operators. Indeed, this equation identifies the importance of each control subcriterion as a sub-category of a goal criterion. Then, the importance of goal criteria is obtained based on the average importance of their relevant control sub-criteria. Finally, considering the numerical values obtained from Formula (1), the ranks of goal criteria are identified. In this regard, the closer the importance of the goal criterion is to 10, the higher the rank of that criterion is. 3. Results & discussion 3.1. The results of planners' negotiations Regarding the results of planners' E-negotiations, the values (objectives) of pipe renewal were identified based on AWWA-M28. In this sense, the purpose of pipe renewal must be to improve the structural conditions and the hydraulic and quality features of the WDSs (AWWA 2014). By determining these objectives, the goal criteria and their effect on the conditions of WDSs (structural, hydraulic, and quality) were specified; the control sub-criteria were then identified. The goal criteria and control sub-criteria resulting from these E-negotiations are shown in Table 3. As represented in this table, 9 goal criteria were identified for planning pipe renewal. These criteria are based on all properties related to the pipes, which directly or indirectly affect water supply conditions in the WDSs. For instance, the pipe properties such as hydraulic, mechanical, material, and events could be effective directly on water supply, whereas the influence of other properties is indirect on WDS conditions. The indirect criteria relate to water, soil, pathway, customers and urban management. As a result of planners' E-negotiations, 31 sub-criteria were identified as controlling variables for goal criteria. As represented in Table 3, the number of control sub-criteria is considerably higher than in previous studies. Some sub-criteria, such as maintenance ease, non-floatable ability, and thermal and seismic resistance, were considered in these negotiations but are uncommon in previous studies. Using experiencebased variables like the ones mentioned above can overcome the data limitations in this industry. This shortcoming was improved in these negotiations. Moreover, numerous sub-criteria mentioned in these negotiations are not practically determinable in the numerical data-based methods (e.g. customers' complaints against the water quality, soil excavation, pipe location in the pathway, potential threats, pipe interference with other urban infrastructure and municipal priorities); while, in practice, these criteria could be decisive for pipe renewal. Hence, using the method proposed in this work helps develop controlling criteria not typically considered by other numerical data-based methods. The knowledge-based method proposed in this research makes it possible to find the pipe renewal factors that are less considered in the data-based methods. Indeed, the knowledge of the experienced experts could work as important as the operational data to identify planning criteria for pipe renewal. This method could be useful, especially in systems where operational data are limited, and extracting data could be faced with costly work. 5 CORRECTED PROOF S. Salehi et al. Utilities Policy xxx (xxxx) 101407 Table 3 The values (objectives), goal criteria and control sub-criteria resulting from planners' E-negotiations. Values (objectives) Improving the structural, hydraulic and quality conditions of water distribution systems using pipes renewal operation Goal Criteria (variables) Direct Indirect 1 2 3 4 5 6 7 8 9 Hydraulic-based Properties of the Pipe Mechanical-based Properties of the Pipe Materialbased Properties of the Pipe Eventbased Properties of the Pipe Waterbased Properties of the Pipe Soilbased Properties of the Pipe Pathwaybased Properties of the Pipe Customersbased Properties of the Pipe Importancebased Properties of the Pipe Control Sub-criteria (variables) 1 2 3 4 5 6 7 8 9 1 Pressure Age Roughness Failure Rate Customers Complaints against the Water Quality Soil Type/ Bedding Pathway Type Customers Combination Potential Threats 2 Flow Velocity Length Lifetime Leakage Rate Residual Chlorine Soil Excavation Pathway Cover Customers Density Pipe interference with other urban infrastructure 3 Flow Diameter Maintenance Ease Thickness of Pathway Cover Customers' Building Age Municipal Priorities 4 Depth Corrosion Pipe Location in Pathway 5 Non-Floatable Ability Pathway Level 6 Thermal Resistance 7 Seismic Resistance Without using the data-based complex analytical methods, it is possible to use simple and robust knowledge-based decision methods for planning many works in urban water management, such as renewal works of water pipelines. Although not obtained from the data-based methods, these plans are based on the deep experience of experts who have been engaged with the water systems for many years. 3.2. The results obtained from the collective knowledge of the system operators The results obtained from the collective knowledge of the system operators in this research are presented in Fig. 4 and Table 4. The results are described and discussed as follows. 1. As shown in Fig. 4, the highest rank was assigned to the goal criterion of “Event-based properties of the pipe”, and the lowest rank was assigned to the criterion of “Soil-based properties of the pipe”. In addition, the criteria of “Hydraulic-based properties of the pipe”,“Importance-based properties of the pipe”, and “Mechanical-based properties of the pipe”are in the second to fourth ranks (Fig. 4). Based on these findings, it can be acknowledged that in 5 provinces, pipe renewal plans are based on the pipe event properties. However, the criteria associated with pipe failures are mainly hydraulic and mechanical variables (Elshaboury et al., 2020b;Salehi et al., 2018b;Yoo et al., 2014; Tabesh et al., 2009;Eisenbeis et al., 2004), are ranked 2nd and 4th, respectively. Therefore, it seems that the event-based viewpoints have more importance in collective knowledge-based methods for renewal planning of the pipes compared to the databased methods, which focus on hydraulic and mechanical variables. 2. According to Table 4, in 5 Iranian provinces, the highest rank is assigned to the criterion of “Event-based properties of the pipe”, and only in the other three cases (provinces of Khuzestan, Sistan and Baluchestan, and West Azerbaijan) the first criterion in the rank is the goal criterion of “Hydraulic-based properties of the pipe”. Since many studies have shown the importance of hydraulic variables in planning pipes' renewal, the results of group decision-making in these three provinces are relatively more accurate. 3. In addition, considering Table 2, it is apparent that compared to the other five provinces, the years' experience of most system operators in these three provinces is more than 20 years (Khuzestan 66.7%, Sistan And Baluchistan 33.3% and West Azerbaijan 50%). Nevertheless, only the operators of Khuzestan province have higher degree levels in these three provinces. The operators' degrees in Sistan and Baluchestan provinces are even lower than the Isfahan province; in this approach, West Azerbaijan has the same conditions as Zanjan province (Table 2). Thus, to investigate the efficiency of the knowledge-based decision methods, it can be concluded that the years of experience of the operators are more relevant than their degree, leading to more practical results. 4. As reported in Table 4 and Fig. 4, in seven provinces, “Hydraulicbased properties of the pipe”are in a higher ranking position than the “Mechanical-based properties of the pipe”. According to the results of recent studies about the criteria affecting the renewal of pipes (Elshaboury et al., 2020b;Salehi et al., 2018b), the results of the collective knowledge-based decision method proposed in this research appear to be reliable. 5. Among the 31 control sub-criteria identified in this research, the sub-criteria “Failure Rate”,“Pressure”,“Potential Threats”, “Pipe Age”,“Customers Density”,“Customers Complaints against the Water Quality”,“Pipe Lifetime”,“Pipe Location in the Pathway”and “Soil Type/Bedding”are at the top of the rank in their respective groups of goal criteria (Fig. 4). It was found that these control sub-criteria are the main variables for pipe renewal in the case studies. 6. Since the control sub-criteria “pipe age”and “lifetime of the pipe”were selected as one of the main criteria by system operators in this research (Fig. 4), it seems that the sub-criteria 6 CORRECTED PROOF S. Salehi et al. Utilities Policy xxx (xxxx) 101407 Fig. 4. The total ranks determined by system operators for goal criteria and control sub-criteria. Table 4 The ranks obtained for goal criteria in each case study. No. Water and Sewerage Company of Province (Highest rank) 1 ≤Goal Criteria Ranks≤9 (Lowest rank) Hydraulic -based Properties of the Pipe Mechanical -based Properties of the Pipe Material -based Properties of the Pipe Event -based Properties of the Pipe Water -based Properties of the Pipe Soil -based Properties of the Pipe Pathway -based Properties of the Pipe Customers -based Properties of the Pipe Importance -based Properties of the Pipe 1 Fars - Shiraz 2 3 6 1 5 9 8 7 4 2 Isfahan 3 6 8 1 4 9 7 4 2 3 Khuzestan 1 4 5 2 8 9 7 6 3 4 Razavi Khorasan - Mashhad 2 7 8 1 4 9 6 3 4 5 Sistan and Baluchestan 1 2 4 3 8 9 7 5 5 6 Tehran (Central + Province) 2 4 5 1 6 9 8 7 3 7 West Azerbaijan 1 4 8 2 6 9 7 5 3 8 Zanjan 4 2 8 1 7 9 5 6 3 related to pipe age have a key role in knowledge-based decisions for pipe renewal. 7. As presented in Table 4, since the goal criterion of “Importancebased properties of the pipe”is ranked 3rd in four provinces and 2nd in one province, it can be concluded that this criterion was considered significant by many operators in this study. This goal criterion comprises control sub-criteria, which are more related to indirect variables other than to other WDS factors. These subcriteria consist of potential threats (social, local or possible terrorist threats), pipe interference with other urban infrastructure (including electricity, gas, and sewage collection networks), and municipal priorities (coordination of pipe renewal plans with urban development programs). Hence, in terms of knowledge-based decision methods, it can be acknowledged that the indirect variables are decisive for pipe renewal. 8. Table 4 and Fig. 4 show that the goal criterion of “Soil-based properties of the pipe”in all eight provinces studied in this research is ranked at the bottom. This fact indicates that the dominant opinion in these case studies is that the soil around the pipe does not significantly affect pipe renewal. However, in most of the references related to the buried pipes (Watkins and Anderson, 2010;Moser, 1990), it has been found that the type of soil around the pipe as well as the quality of the pipe bedding can have a direct effect on pipe failures; and consequently, pipe renewal planning. Consequently, it can be concluded that some findings of collective knowledge-based methods can conflict with the results of data-based methods. 9. As illustrated in Fig. 4, it is clear that the goal criteria of “Customers-based properties of the pipe”and “Pathway-based properties of the pipe”are in lower rank positions than the hydraulic and mechanical criteria. Since many studies defend that hydraulic and mechanical variables are relevant to detecting and predicting pipe failures (Zerouali and Zerouali, 2021;Moghaddam et al., 2021;Winkler et al., 2018; 7 CORRECTED PROOF S. Salehi et al. Utilities Policy xxx (xxxx) 101407 Scheidegger et al., 2015); it seems that the knowledge-based decisions are aligned with data-based methods in this issue. 10. As shown in Table 4, the goal criterion of “Water-based properties of the pipe”has received a relatively low rank compared to other criteria; concretely; this criterion is ranked 7th and 8th in 3 provinces and 6th in 2 provinces. These ranks indicate that the quality problems of water supply are considered less important by system operators in the case studies, whereas, as previously mentioned, the objective of pipe renewal must be to improve the water supply's structural, hydraulic, and quality conditions system (AWWA 2014). Therefore, although the collective knowledge-based methods can be helpful in planning pipe renewal with limited data, the objectives of pipe renewal for improving the quality variables of water supply should not be ignored. 11. Based on the findings presented in Table 4, the criterion of “Material-based properties of the pipe”is a criterion that was ranked from 4 to 6 positions in 4 case studies; whereas, in other 4 Iranian provinces, this criterion is in the 8th position (Table 4). These rank positions highlight the diverse point of view regarding the role of the pipe material by the operators of the different provinces. This finding indicates that the results of the knowledge-based decisions are not similar in all systems, and the experience of operators could be different according to their case study. 4. Conclusion Water pipe renewal plans are among the most critical decisions for water and sewerage companies. However, these decisions are usually based on WDSs operational data, which are not always recorded coherently. Given these limitations, using the data-based methods for renewal planning in these systems can be impractical. A hybrid knowledge-based method is proposed in this research to overcome this shortcoming and identify planning criteria for pipe renewal. For this purpose, the planning criteria for pipe renewal were identified using the electronic negotiations of 17 knowledgeable planners and based on the evolutionary system design method. Then, these criteria were ranked by knowledge-based group decisions of 48 system operators and based on the nominal group technique. The results obtained from this study indicate that the proposed method can be used to identify planning criteria for pipe renewal in WDSs when using complex analytical-numerical data-based methods is impractical. Indeed, relying on the findings of this research, it is concluded that the knowledge of experts could be as important as numerical data in the policymaking process of each field in public utilities (e.g. planning pipe renewal). Since the data in the field of public utilities are uncertain and imprecise, using the data-based numerical methods for the analysis of these utilities and making any policy in this field is not reliable. Therefore, the planning knowledge and professional experience of experts who have been engaged with the utilities for many years could aid in decision-making in the field of public utilities and making up the problems which are not solved by data-based methods. Additionally, in this research, it was found that in knowledge-based methods, the pipe events are more frequently considered than in databased methods, which give more importance to hydraulic and mechanical variables. The results reveal that the hydraulic and mechanical variables are considered significant according to the two methods. In addition, it was found that some criteria like variables related to urban management are usually considered by knowledge-based decisions for pipe renewal, whereas these criteria are not considered in data-based methods. However, some findings of the proposed method conflict with the results of other data-based methods. For instance, the criteria of water quality and soil properties around the pipes are ranked at the bottom. Hence, although using the collective knowledge-based methods can be useful for WDSs with limited data, it seems that the increase in the experience of operators may provide a more comprehensive view of the planning criteria for pipe renewal. In addition, this method cannot substitute for comprehensive strategic planning to implement all details of renewal works of water pipelines; along with the proposed knowledgebased method in this research, using the data-based method could be inevitable in systems in which it is possible to extract the operational data. Moreover, since the proposed method's results depend on Iranian experts, verifying the results in various regions is essential. In this research, although the six provinces were studied, increasing the number of case studies in various countries could lead to obtaining the results with more reliability. Thus, we suggest comparing the obtained results from this research with studies in other countries. In addition, we recommend that future research compares the results of the knowledgebased methods with those of the data-based methods for pipe renewal by investigating the case studies in more detail to verify the results of the proposed method. Code availability Not applicable. Consent to participate Not applicable. Consent for publication Not applicable. Ethics approval Not applicable. Funding Not applicable. Author contribution It is acknowledged that all authors have contributed to accomplishing this research and writing this paper, respectively: Sattar Salehi, Alicia Robles Velasco, Ali Seyedzadeh, Aliakbar Ghazali, Mohsen Davoudiseresht. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Data availability Data will be made available on request. Acknowledgements The authors of this research would like to thank the following experts for their generous contribution and efforts: Eng. Masoumeh Mahdibadi, Dr. Ali Zarei, Eng. Ghasem Hashemi, Eng. Mohammad Kasravi, Eng. Rouhollah Tavakoli, Eng. Mojtaba Akbarian, Eng. Mehdi Osat, Eng. Ehsan Sabeti Aminaei, Dr. Mohammad Salarian, Dr. Mehrdad Zaboli, Eng. Mohammadhossein Masoudi, Eng. 8