Water sensitive urban design (WSUD) approach for mitigating groundwater depletion in urban geography; through the lens of stakeholder and social network analysis Open Access

Water is the largest resource used by cities (Wolman 1965; Kennedy et al. 2011). If an urban area is analyzed through the lens of urban metabolism, water is the largest and maybe the main material that enters the urban region (Wolman 1965; Hermanowicz & Asano 1999). Besides, urbanization invariably causes more water pollution, flooding risk, and water scarcity, as well as shrinking groundwater resources due to over-extraction (Lu 2007; Yao et al. 2008; Liu & Zuo 2009; Huang et al. 2013).

The management of water resources-related issues, especially groundwater, has special conditions due to the ease of accessibility and their large scale compared to other natural resources. Groundwater supplies about 36% of drinking water and about 42% of agricultural water; hence it is a key freshwater resource globally (Scanlon et al. 2012; Kourakos et al. 2019; Ashraf et al. 2021). In this case, other aspects of natural environment management, such as social issues, must be considered and integrated with the resources management. Integrated water resource management can be considered an interesting concept in water resources management (Smith & Clausen 2015).

Urbanization increases from 13% in 1900 to 70% in 2050 (United Nations 2012), and consequently, this makes urban water system management much more important and complicated. The main reasons for the importance of urban water resources are (i) high sensitivity of water quality in an urban area; (ii) the significant amount of returned water or wastewater; (iii) the populous regions, which are covered by urban water systems; (iv) water consumption diversity in an urban area; (v) high risk of water-related events such as flood, drought, and urban water system pollution; (vi) the impacts of urbanization such as water resources degradation; and (vii) the heat island issue in an urban area. These are the main subjects in the study of urban water system management.

One of the most important effects of inappropriate water resource utilization for urban development is excessive groundwater use from the aquifer, leading to land subsidence. Land subsidence is considered a global problem due to long-term excessive groundwater withdrawal (Mahmoudpour et al. 2013). Thus, applying an integrated approach in dealing with various urban water aspects is necessary according to the mentioned issues.

Due to the interaction of urban planning and water resources, water sensitive urban design (WSUD) approach has been developed. WSUD can be defined as a land planning and engineering design approach that integrates the urban water cycle, including stormwater, groundwater and wastewater management, and water supply, into urban design to minimize environmental degradation and improve aesthetic and recreational appeal (Lloyd et al. 2002b; Kuller et al. 2017). WSUD is an answer to applying traditional water resource approaches in urban design and planning concepts, especially in arid and semi-arid areas. WSUD considers urban water cycle aspects a valuable resource (Sharma 2017).

In addition to the mentioned aspects in an urban area, several stakeholders with various desires and interests are located and participate in urban management. In some cases, these conflicting desires make urban water resources management and preserving the urban hydrological cycle more complicated. In this situation, it seems necessary to find solutions placed on the overlap of stakeholders' interests; hence, from this point of view, WSUD can be imperative and needs to be studied. For this reason, in this article, the importance of the WSUD approach is examined from the perspective of the stakeholders' issues.

WSUD originated in Australia's hydrological environment (Whelans & Maunsell 1994; Ahammed, 2017), and the first guideline of WSUD was released in Western Australia in 1994 (Whelans & Maunsell 1994). New Brompton Estate in Australia was the first residential development where WSUD principles were applied for on-site stormwater management (Hopkins & Argue, 1994; Barton & Argue, 2015). The performance and development of this system have been argued by Hopkins & Argue (1994), Johnston et al. (1995), and Barton & Argue (2015).

Kazemi et al. (2018) applied the WSUD approach to deal with salinity problems in an urban area. This paper's primary objective was to examine the effect of harvesting surface runoff with a ranging salinity using a permeable pavement to supplement the water demand of a bioretention system of an equal plan area. This study's main purpose is to investigate the importance and effect of WSUD tools on water salinity.

Kuller et al. (2017) considered the WSUD approach to responding to sustainable management in an urban environment. This paper has mentioned that to have a successful WSUD approach, the following three principles should be considered: (I) Considering all relevant technical, social, and economic approaches in WSUD development; (II) Considering all relevant scales of the problem; (III) Considering all relevant stakeholders in an urban area to develop the WSUD approaches. Although this study emphasizes the importance of developing tools based on WSUD from various stakeholders' perspectives, in previous studies, the technical and economic aspects of WSUD are considered.

In this regard, Brodnik & Brown (2018) are one of the studies in which stakeholders' role has been emphasized as pivotal in changing dominant practices in stormwater management, but the types of agency processes best suited to develop such conditions are not well studied. Brodnik & Brown (2018) address the mentioned gap using empirically investigating how institutional entrepreneurs developed transformative capacity in a successful case of dominant practice change: stormwater management with WSUD in Australia's urban water management sector.

A key point in Brodnik & Brown (2018) is looking at WSUD tools as not an incremental improvement of the traditional stormwater management practice but a radically different approach that challenges and erodes the institutional foundations on which conventional practices rest. Hence, based on the mentioned concerns derived from Brodnik & Brown (2018), WSUD must be considered from an instrumental and an institutional perspective.

Studying WSUD from a physical perspective as well as social and stakeholder perspective in the urban environment is necessary. In other words, due to the entanglement of the social and physical part of urban geography, studying WSUD from a social lens and identifying its necessity from this point of view along with considering its efficiency from a physical perspective must be considered necessary. Social network analysis and stakeholder analysis can be used to study the social aspects related to the stakeholders present in urban geography.

Social network analysis and stakeholder analysis approaches can be practical, given the importance of studying the stakeholders' role in an urban community. Social network analysis depicts, models, and analyzes a community of agents using a network structure with nodes and links representing participating stakeholders and their relationships (Ahmadi et al. 2019). The social network analysis approach can be practical in an urban environment, including various stakeholders with different interests, especially in cooperation and conflict. Social network analysis has been widely applied in the governance and use of natural resources shared between several stakeholders (Schneider et al. 2003; Dougill et al. 2006; Bodin et al. 2006; Ernstson et al. 2008; Lauber et al. 2008; Bodin & Crona 2008; Mandarano 2009; Haak et al. 2017; Pahl-Wostl 2002; Yamaki 2017; Luzi et al. 2008; Navarro-Navarro et al. 2017; Emami-Skardi et al. 2020).

Stakeholder analysis is one of the most imperative approaches to studying stakeholders' powers and interests in a system. Stakeholder analysis and social network analysis can give a comprehensive picture of the community of stakeholders and the relationships between them in a complex urban environment. Stakeholder analysis has been applied in forest landscape management (Paletto et al. 2015), basin management (Ogada et al. 2017; Yang et al. 2018), and urban water allocation (Ahmadi et al. 2019; Emami-Skardi et al. 2021).

In this study, the WSUD approach is considered to mitigate the urbanization effects on the natural water cycle. In this regard, the present study has two main sections. First, in the social section, considering the presence of various stakeholders in urban geography, the importance of the WSUD approach as a conflict resolution tool is studied. In other words, in this section, the WSUD approach is described from a social perspective and as a conflict resolution approach, especially between developing and protecting stakeholders.

In the physical part, the emphasis is on examining and estimating the effectiveness of tools based on WSUD in reducing aquifer decline in an urban area. In brief words, the social sector emphasizes the importance of the WSUD approach, as the WSUD approach tries to preserve the natural water cycle while maintaining many land uses, which is vital for developing stakeholders. And in the physical sector, by achieving the above knowledge from the social perspective, the efficiency of WSUD tools based on the WSUD approach is evaluated.

In the following parts of this paper, first, considering water issues in urban planning and design is presented. Then, using the stakeholder analysis approach, the position and role of the key stakeholders in an urban area are studied and using the stakeholder analysis approach, the WSUD approach's role is presented based on the stakeholder analysis concept. Besides, social network analysis is considered to investigate the relationships between the stakeholders in an urban area. Social network analysis can highlight the conflicts between stakeholders in an urban environment and show the importance of WSUD in resolving disputes between the developing and protecting stakeholders.

This redefinition of the WSUD concept through the lens of social network analysis and stakeholder analysis will ultimately emphasize the position and importance of the WSUD concept as an imperative conflict resolution approach in an urban area. This research studies an urban environment, namely the western part of Tehran city, using a behavioral-physical simulation model. Using the developed behavioral-physical simulation model, WSUD tools are applied to find solutions for some of the main water issues of urbanization. Land subsidence is one of the main urban planning and design issues in the western part of Tehran city due to groundwater extraction. In addition, to present the applicability of the WSUD based tools in this area, three main WSUD methods, namely porous asphalt, rubber dam, and wetlands, are considered in the physical-behavioral model to mitigate the groundwater depletion problem in this region.

Since using social-based approaches in studying WSUD and its application in an urban area is a new issue, the importance of stakeholder-based approaches in urban planning and management needs to be clarified. We try to answer the following question: Why are social-based approaches necessary for studying water and environmental issues in an urban area? Hence, to present and clarify the role of the WSUD approach in an urban region, we must first peruse the urbanization processes with an emphasis on water-related issues.

Land prices in urban areas have increased with urban development and human settlement. Urban development and land value growth have led to significant influences on natural resources (Huang et al. 2010), ultimately resonating with the structural approaches. As a result, the stakeholders in charge of urban development based on structural approaches gradually gained power. For example, officially, municipalities in Iran were among the first urban institutions that date back to 1907 in a new form (Imani-Jajarmi 2020). With the growth and expansion of cities, problems such as heat islands, air pollution, increased crime, increased marginalization, uncontrolled abstraction of water resources, and land subsidence occurred (Karamouz et al. 2010; Emami-Skardi et al. 2021). As environmental problems increased, institutions were established to protect natural areas. For example, the Department of Environment Organization in Iran was established in 1971 (Dabiri et al. 2010), clearly years after establishing municipalities. With the creation of conservation institutions due to the need to protect the environment and natural resources, the conflict between development and conservation institutions also increased. The formation of various institutions in the urban environment and the conflict between them have made managing natural resources, such as water resources, an interdisciplinary issue (Huang et al. 2010). Studying urbanization and its effects on water resources from the perspective of social studies can be very effective in analyzing and resolving inter-institutional conflict (Ahmadi et al. 2019).

At the beginning of urban development, developing stakeholders were more powerful than other ones (Figure 2(a)), and this largely led to the development without preserving the environment and the natural water cycle (Figure 1). After this point, crises emerged because of the neglect of water resources management and environmental issues.

With the onset of these crises, serious doubts arose about urban management's norms, beliefs, and core values, especially in water resources management and engineering-related problems. This condition led to the learning of new approaches and institutional structures in urban water resources management and consequently led to the development of protective institutions. This process can be categorized in the social learning concept, which can be considered the changes and modifications in the norms, beliefs, and values towards the sustainable use of shared resources (Emami-Skardi et al. 2021).

The process of the creation, development, or strengthening of the protective institutions is presented in Figure 2(b). After this condition and over time, the protective institution became more powerful (Figure 2(c)); this is when it is necessary to use an appropriate approach to satisfy urban development and natural water cycle demands related to developing and protecting stakeholders, respectively. The WSUD approach can be considered through the lens of social attachments in an urban area. WSUD can be considered as the structural and nonstructural approach embedded in the urban planning and development method, which ultimately can improve the natural water cycle, and at the same time, maintain the imperative performance and task of the urban areas. Briefly speaking, WSUD can provide the desirability of both protection and development institutions and, while protecting the natural water cycle, also have the desired functions of the development institution.

In this section, the flowchart of the methodology is presented in Figure 3, then the details of each part will be explained separately. The proposed methodology has two main sections: the physical-behavioral model for urban water cycle simulation and the social-based part for investigating the stakeholders' power, interest, and relationships in the study area.

System recognition and identification are the first steps and prerequisite parts of developing the WSUD approach. In an urban hydrological environment, system recognition includes physical, social, and behavioral parts.

One of the most important reasons for the development of WSUD is the physical environment. In other words, WSUD can be considered an attempt to live in arid and semi-arid conditions by reducing the effects of urban development on the natural water cycle. In this regard, physical identification is the first step in system recognition (Emami-Skardi et al. 2013). Then physical recognition can lead to a physical model; in this paper, the central core of the physical-behavioral model is adapted from Emami-Skardi et al. (2020), which can be considered for further details in this regard.

and considered as the volume of water (downstream and upstream) of the river at the time step, respectively. and are the volume of water extracted from the river for gardens and agricultural activities, infiltration of water from the river to aquifer and wastewater inflow to the river at time step, respectively. and are represented the amount of needed water for green space, drinking, agriculture, and the industry at time step.

and indicating the return flow from municipal, potable, agriculture, industry, and gardens consumption at the time step. And is wastewater return flow to the wells in the time step. is the water table and is evaluated for each time step from Equation (4).

In the social studies section, the propositions presented in this research on the importance of WSUD as a conflict resolution approach in an urban environment are investigated by analyzing an urban environment's social conditions.

Stakeholder analysis is a practical and effective approach to evaluating the powers and stakeholders' interests in a shared environment. Stakeholders are natural or legal persons that can affect or be affected by the actions and decisions made to govern a system (Grimble & Wellard, 1997; Reed et al. (2010); Emami-Skardi et al. 2021). Stakeholder analysis has three main classifications (Emami-Skardi et al. 2021), stakeholder recognition, then the classification of the stakeholder, and finally, studying the relationships between the stakeholders.

The primary step in stakeholder analysis is determining the main stakeholders and identifying the natural or legal persons who hold a stake regarding the specific social or natural issue (Emami-Skardi et al. 2021). The stakeholders can be grouped based on their desires and characteristics. The interview is a practical way to gather needed data and information. Interviews can help identify the actual conditions using informal data that can be neglected when only formal aspects are considered. Hence, the quantified values of power interest can be obtained using interviews with the key stakeholders.

As highlighted in this study, due to the process described in Figures 1 and 2, developing and protective stakeholders in urban environments may have conflicting relationships. Social network analysis is a practical approach to verifying and determining a claim. Social network analysis is mainly based on forming and studying the existing relationships among stakeholders. Thus, social network analysis provides a realistic picture of the relationships between the stakeholders in the system. Various models such as UCINET, NETDRAW, and Gephi are applicable software in studying, presenting, and depicting a network of stakeholders (Borgatti 2002; Bastian et al. 2009; Ahmadi et al. 2019; Emami-Skardi et al. 2021). In this paper, Gephi is considered to study social network analysis.

Higher values of means the stakeholder j is generally more central, and more stakeholders have institutional relationships with stakeholder j (Ahmadi et al. 2019). In other words, the value of denotes the number of stakeholders who have chosen the stakeholder j as a natural or legal person with formal or informal relations besides representing the related strong of these relationships. The higher values of indicates that the stakeholder i have more robust relationships with more stakeholders.

It should be considered that and have direction and must be interpreted from this perspective; hence a stakeholder with a higher value of out-degree centrality has easy access to other stakeholders and may influence them (Ahmadi et al. 2019).

WSUD includes a wide range of structural and nonstructural methods, which can be found in Sharma et al. (2018). Based on the previous studies and the characteristics of the study area, besides the main water-related issue in the study area of this paper, namely groundwater depletion, porous asphalt, wetland, and rubber dam, are considered the three main types of WSUD approaches to mitigate the effects of the urban development. These three methods are be introduced below, and more details are given in the case study section.

It should be emphasized that the purpose of the WSUD approach is not to disrupt the main urban development plans but to mitigate the effect of urbanization on the hydrological water cycle using the embedded potentials in the development plans. With this in mind, porous asphalt is one option to protect the urban water cycle; besides, the function and performance of the urban lands do not change significantly. Of course, porous asphalt development has its limitations, the most important of which is the impossibility of developing it on main streets due to its load-bearing limitations. For this reason, in this study, the development of porous asphalt in side streets is considered. This study shows that the precipitation that rains on the porous asphalt is considered groundwater recharge. In other words, the land is considered permeable in areas where permeable asphalt is used.

Groundwater recharge wetlands are human-made wetlands constructed to recharge the aquifer gradually. Wetland can be so helpful in the groundwater's sustainable use (Kamp & Hayashi 1998). Various tasks can be considered for a wetland, such as water treatment, groundwater recharge, and recreational landscape; in this paper, it is mainly considered as a groundwater recharge tool; wetland is mainly considered in the large green spaces where it should be designed to catch the surface water and recharge it to the groundwater.

Due to the characteristics of urban land covers, there may not be much land to develop artificial aquifer recharge in urban areas. In this condition, the rivers and waterways can be a particular chance for groundwater recharge. Rubber dams are practical tools in urban areas within a river for the mentioned purpose. The rubber dam is an inflatable and deflectable hydraulic structure installed worldwide for various purposes (Zhang Tam & Zheng 2002). Interestingly, the first rubber dam was installed in the USA in 1950 for groundwater recharge (Kahl & Rauell 1989; Plaut et al. 1998; Zhang Tam & Zheng 2002). The rubber dams' main advantages are collecting debris and preventing it from entering the waterways and the simple construction and operation. Although the rubber dams are mostly light with a uniform load, the dam site should always be solid and concrete (Zhang Tam & Zheng 2002).

In this paper, for the rubber dams' site selection, the geomorphic, hydrological, meteorological, and hydraulic factors are considered based on Zhang et al. (2002). The dam foundation level should be higher than the downstream riverbed to prevent abrasion. The rubber dam's downstream slope should be about 1 to 4 (1 vertical and 4 horizontal) for safety. The dam site should be in a straight river section where the river flow is slow and the slopes are stable (Zhang et al. 2002). Then, there should not be a sudden change in the hydraulic condition for the rubber dam site selection. The case study section presents more details about porous asphalt, wetlands, and rubber dams.

The western part of Tehran, shown in Figure 5, due to the Kan River in the middle of this urban area is named the Kan River basin (Emami-Skardi et al. 2020). Surface water, groundwater, and treated wastewater are the three main water resources (Moradikian et al. 2022). This urban area can identify various and different land covers and, consequently, different water demands. The growing urbanization and related water needs are presented in Table 1.

The main Kan River basin land-uses are agriculture, residential, a large recreational lake, green spaces, and industrial areas (Darbandsari et al. 2017). The study area starts from the northern part of Tehran city and ends at the old Tehran-Qom Road south of the region. The eastern and western boundaries of the area are defined perpendicular to equipotential lines of groundwater (Emami-Skardi et al. 2020); hence, the assumption of the lack of water flowing from the eastern and western boundaries can be acceptable (Darbandsari et al. 2020) (Figure 5).

The Kan River basin can be considered a developing urban region with serious water supply, agricultural, green space, and industrial water demand besides several major environmental issues (Khorasani et al. 2018; Ahmadi et al. 2020; Emami-Skardi et al. 2020). This basin also suffers from policy-related concerns that mainly come from conflicts among stakeholders, such as the conflicts over the allocation of treated wastewater (Ahmadi et al. 2019; Eyni et al. 2021). The average annual precipitation in the study area is 230 mm. The Kan River basin includes four main types of water users, and the current water demands and the volume of water withdrawal from ground and surface water resources are presented in Table 1.

This urban area is a challenging and interesting case for studying the proposed claims and approach in this paper based on the following reasons (Ahmadi et al. 2019; Emami-Skardi et al. 2020): (a) Covering some rapidly growing populated regions besides some of the main industrial areas; gardening areas, and agricultural regions in the north and south of the Kan watershed, respectively; (b) it is a modern populated urban region with a closed adjacency relation with husbandry areas, including some new human-made recreational areas; (c) illegal water withdraws from the surface and groundwater resources, and; (d) several involved stakeholders with different and in some cases conflicting characteristics and interests.

Figures A1 to A4 in the appendix show the land-use changes in the study area between 1992 and 2016, which confirm the complexity of land use, increasing the density of residential and urban areas, diversity of water demands, and being impermeable of the lands in this study area during these years. This region may be considered one of the fastest-growing urban areas in the Middle East.

Development and urbanization in arid and semi-arid regions with low rainfall and high evaporation put high pressure on groundwater resources and may accompany development with external costs such as land subsidence.

The western part of Tehran city is one of the most complex urban areas in the Middle East, and infrastructure problems in the area have recently exacerbated land subsidence. This area has one of the highest groundwater depletions besides the highest land subsidence in Iran (Ashraf et al. 2021). Figure 6 shows the critical situation of groundwater resources in Iran, especially in the study area.

The main pressure in arid and semi-arid regions is to supply water to the aquifers, leading to land subsidence (Mahmoudpour et al. 2013). The southwestern part of the basin is subject to land subsidence, caused mainly by groundwater withdrawal (Mahmoudpour et al. 2013). Land subsidence can have significant impacts on urbanization and urban infrastructures. Since 2003, the study area has expanded greatly from urbanization, and various land uses have emerged in the western area of Tehran. Over the past 28 years, the groundwater level has decreased 11.65 m and resulted in land subsidence (Mahmoudpour et al. 2013).

The expansion of the land subsidence from the southwest to the northwest of Tehran has gone so far that it covers almost all of International Mehrabad Airport, coinciding with the city's expansion to northwest Tehran. For this reason, urban development plans and management based on water-sensitive urban design should consider and prevent land subsidence.

The main stakeholders at the institutional level are identified as the key legal agent in this study area. Based on the previous studies in the Kan River basin and using a pre-interview with key professionals, the main stakeholders are recognized besides by applying the snowball sampling approach. In addition to the mentioned approach, the physical characteristics (such as the land cover, main water resources and related infrastructures, political and hydrological borders, and water demand) of the Kan River basin were considered the main issues of the system identification. The main stakeholders are presented in Table 2 (Ahmadi et al. 2020; Emami-Skardi et al. 2020).

Ahmadi et al. (2019) suggested that the selected stakeholders can be categorized into some main groups, such as protective and developing (Table 3).

The necessary data were collected using a survey. The survey consisted of three main sections: data for stakeholder analysis and social network analysis using closed questions. To study the case study using the stakeholder analysis approach, the interviewees are requested to describe their positions in the system and determine each organization's power and interest. Also, respondents were requested to determine all the other organizations' powers and interests. In other words, the stakeholders answered about their power and interest and the interest and powers of the other one's using five-point Likert scale. The stakeholders' average answers are presented in Table A1.

The respondents were also asked to describe other stakeholders with whom they have relationships in managing the urban water resources in the study area. In this regard, the respondents were requested to answer the scale of conflicting relationships and to calculate all questions' magnitude, and a five-point Likert scale was applied.

In this research, according to the social-based methods, the imperative of the WSUD approach is studied. First of all, stakeholder analysis is applied in the studied area, and the related results are discussed to clarify the interest and powers of the main stakeholders regarding water issues in the studied region. In this part, the importance of defining and the intermediate approach position, here WSUD, is emphasized to deal with the water-related issues in an urban area. Then, using the social network analysis approach, the main conflicts in an urban area in dealing with water-related issues are studied, and the position of WSUD is presented as a conflict resolution technique in the studied urban area.

Considering the gathered data from ten organizations, the main and first stakeholder analysis approach is presented in Figure 7. This figure presents comprehensive information about the stakeholders' interest and power in a grid form where the power is depicted versus the interest. This method of depicting power versus desire can help compare these two parameters for a stakeholder and help to compare the above parameters between two or more stakeholders. In this condition, it would be possible to study the mentioned process for the importance of the WSUD approach to resolve conflicts between the stakeholders in the engineering and management of urban water resources.

As previously mentioned, key stakeholders in the system were recognized using the snowball method and then categorized into two main classes: protecting and developing stakeholders. After analyzing, studying, and interviewing stakeholders' power, interest in the system is attained and presented using Figure 7.

Social network analysis is a way to show a realistic picture of the relationships between stakeholders in a system. A comprehensive form of a social network analysis approach to the types and intensities of the relationships can also be evaluated and presented. This paper uses the social network analysis approach to investigate the groundwater resource management issue regarding the study area's main water-related problems. Groundwater quantity management issue is considered the main topic to be studied through social network analysis.

Since one of the most critical common problems between urban development and water resources management and engineering in the study area is land-subsidence due to overdraft groundwater extraction, the quantitative management of groundwater resources has been studied from the perspective of social network analysis. Figure 8 presents the social network analysis of groundwater quantitative management issues using Gephi Software.

In the previous section, the results of social-based studies are presented. This section presents the results of physical simulation studies using WSUD tools. The physical simulation model has been studied in two main conditions according to the WSUD-based approach, with and without aquifer recharge, using WSUD tools. The WSUD tools have been embedded in the physical models. Based on the main criteria and issues in the materials and methods section.

According to the criteria stated in the previous section, Figure 9 shows the locations of the WSUD tools in this region; for each of the WSUD tools, a higher-resolution picture is presented. Wetlands in parks and green spaces have been placed to receive surface runoff, especially in region 1, and finally, recharge the groundwater. Porous asphalt in dense urban areas and rubber dams are mainly used in regions 2 and 3 to recharge the aquifer, where the construction and management of the rubber dams are much more possible.

In this section, we presented the results of the WSUD function and its importance in groundwater recharge. Since one of the possible actions in this area is not to discharge the treated wastewater of the municipal sewage network to the aquifer, this scenario is also evaluated. Figures 10–12 are three main conditions related to groundwater management and recharge in this region. In Figure 10, no recharge aquifer using the wastewater is implemented, and no WSUD tools are considered. In Figure 11, recharging the aquifer using the wastewater, but no WSUD tools are implemented. In Figure 12, both groundwater recharge and WSUD tools are considered.

Since the general structure of this study is presenting and clarifying the consideration and importance of WSUD from the social and physical perspective, the discussion section has two main parts; firstly, the social-based results are presented and discussed, and in addition, the results of the physical-behavioral part for groundwater recharge using wastewater and WSUD approaches are illustrated.

In this section, and according to the results, protective stakeholders such as TRW and developing stakeholders such as TM can potentially conflict. The section based on the stakeholder analysis showed that protective stakeholders achieved a better position in power and interest to participate in urban water management over time.

Considering the urbanization, as shown in Figures A1 to A4, and regarding the rise of the power of protective institutions such as DOE and TRW, the likelihood of conflict between developing institutions such as the TM, MRUD, and MIMT with protective organizations will increase. The stakeholder analysis can make vivid the roots of the mentioned growing conflicts.

In addition to the stakeholder analysis results, which shed light on the roots of the conflict between the protective and developing organizations, the social network analysis method can clear the present conflicts in the stakeholders' relationships. In other words, the social network analysis section results reveal the conflicts between the protective and developing stakeholders. For example, the TM stakeholder is in the center of the water resources management issues in general and quantitative groundwater management networks.

In the physical-behavioral section, there are three main conditions. Firstly, no solution has been considered for recharging the aquifer using municipal wastewater, and no WSUD tools are considered. The graphs related to this section show that if no recharge for the region's aquifer is considered, there will be a serious crisis, especially in the study area's subsidence. In the second part, urban wastewater is used to recharge the aquifer, but no WSUD tools are used. Although the groundwater table's condition has improved a lot in this section, some serious issues related to groundwater depletion in the aquifer can still be identified. In the third section, using WSUD tools, some of the problems related to land subsidence and aquifer decline can be more controlled than in the second part, but it will still be necessary to use nonstructural and managerial tools in addition to the structural considerations.

Although the benefits of WSUD have been accepted, due to some differences with previous traditional urban planning approaches, it is necessary to provide a framework to make it practical. Lack of coordination between the urban planning and design responsible organizations and water resource management and engineering-related organizations is one of the obstacles to the utilization of a WSUD-based approach.

Part of the destructive effect of urbanization has been on the natural hydrological cycle. Hence, the importance of protecting the hydrological cycle against the unintended consequences of urbanization has necessitated new approaches to integrate urban design and planning with water resource management and engineering-based concepts. WSUD can be applied to mitigate urbanization effects on the hydrological water cycle.

One of the most important characteristics of urban environments is the presence of various stakeholders. The presence of stakeholders in an urban area with limited land resources is fertile for conflict. In the present study, the cause of the conflict and what stakeholders this conflict can occur between were examined from the perspective of stakeholder analysis. Also, in this research, social network analysis has been used to express and determine the intensity of the conflict and its type between different stakeholders. The importance of the output of this section is to examine and express the importance of the WSUD from a social perspective and as an approach to conflict resolution. Then, after studying the WSUD approach from a social perspective, to explain its position as a dispute resolution approach, a physical-behavioral simulation model was used to study the efficiency of WSUD approach-based tools in an urban area. The mentioned study process in the catchment area of west Tehran, which faces falling groundwater levels and land subsidence, has been studied.

From the perspective of stakeholder analysis, due to the high interest and power of protecting and developing stakeholders, considering their different desires, there is a serious potential for conflict in this study area, which is reflected in municipal and regional water stakeholders as the development and protecting stakeholders, respectively. Social network analysis confirms the intensity and extent of the mentioned conflict between development and protecting institutions in the mentioned range. From a social perspective, the WSUD approach, because it can simultaneously meet the development needs of an institution such as a municipality, creates a chance for a protecting institution such as regional water to bring the water cycle closer to its natural state and feed the aquifer.

In addition to this study, the following ideas can be considered. 1. Investigating the effect of climate change on the WSUD based management approach in the urban area; 2. Considering social learning as one of the most imperative approaches in the participation of the stakeholders in the social-hydrological systems; 3. Considering uncertainties in the physical model; 4. Applying other tools based on WSUD, especially nonstructural approaches; 5. Considering game and graph theory approaches for investigating further cooperation over the implementation of WSUD-based tools; 6. Last but not the least, considering a social model of the system for studying the changing of the conflicts of the system towards collaboration to implement the plans presented in this research.

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