**1. Introduction**

According to the recent reports published by United Nations, the population of the world has been estimated at 7.7 billion people in 2019 and projected to continue its increasing trend to around 8.5 billion in 2030, 9.7 billion in 2050, and 10.9 billion in 2100 [1]. Furthermore, it is predicted that most of the world population will live in urban regions rather than rural areas. The growth of the urban population faces some challenges, including unsuitable urban planning and management, insufficient public services, social and cultural anomalies, economic problems associated with urban poverty, environmental contamination, and supplying secure and sustainable water [1,2].

Amongst the aforementioned urban challenges, the water supply is one of the most serious. Concerning water supply, water withdrawal from renewable resources, water transfer, treatment of wastewater, water allocation for several demands, satisfying security and sustainability, and consensusseeking among urban stakeholders with different preferences are the main issues [2,3]. Therefore, the water supply issues should be met by implementing desirable water strategies, which consider multiple sustainable development criteria [4]. Additionally, the several preferences of multiple stakeholders regarding the relevant water demands should be satisfied and group consensus could be achieved [5]. Accordingly, Parkinson et al. have presented the integrated urban watershed management (IUWM) approach, which has been developed for better management of water and wastewater strategies in an urban setting [6].

One of the most complicated challenges for implementing IUWM is increasing the variety of sustainable development objectives, including water resources sustainability, environmental sustainability, socio-economic sustainability, and the related criteria [4,7]. This has led to a serious problem for selecting the more desirable urban water strategy, by which the sustainable development objectives and the important relevant criteria should be satisfied, in addition to achieving the group consensus among the stakeholders. Accordingly, implementing IUWM requires evaluation of the water strategies for supplying the urban demands, while considering the sustainable development criteria and the final group agreement [8,9].

The other significant challenge for implementing IUWM is related to the variety of risk-taking attitudes of stakeholders' groups [10]. The risk-taking attitudes represent the number of criteria that should be satisfied by the urban water strategies [11,12]. The risk-taking cases, which are identified by the risk-taking degrees, are expressed by some linguistic phrases such as "selecting the more desirable strategy for satisfying all criteria" in the completely risk-averse viewpoint, "selecting the more desirable strategy for satisfying at least one criterion" in the completely risk-prone standpoint, and the other cases between these two limits [13,14].

In order to take on the aforementioned challenges, an appropriate model for IUWM should be developed to consider the sustainable development objectives, risk-taking attitudes of stakeholders, and a final group consensus in evaluation of urban water strategies. Simonovic and Bender analyzed the collaborative planning-support system (CPSS) model, as the subset of the decision-support system (DSS) model, which considers all relevant aspects of sustainable water resources planning and management, especially in the process of criteria selection [15]. In the group decision support system (GDSS) approach, the main three issues, such as selection of criteria, generation of alternatives, and evaluation of alternatives based on the criteria are considered based on the balancing and reinforcing aspects for better decision analysis [16–18]. Accordingly, developing a group decision-support system (GDSS) model within an urban watershed needs to analyze a multiple criteria decision-making (MCDM) process, in which the final criteria and water strategies are selected, the strategies are evaluated with respect to the criteria, and the water strategies are ranked for several risk-taking cases.

For analyzing the MCDM process in a GDSS model, a large variety of methodologies have been utilized, of which the most frequently used methods have been well demonstrated in the literature [19]. The most important methods are classified into four categories, including: scoring methods [20], distance-based methods [20–23], outranking methods [20,24–26], and pair-wise comparisons methods [27,28]. The differences between these methods are related to their strategies for solving MCDM problems.

For risk analysis in the MCDM process, some of the risk-based methodologies have been utilized. The most commonly used method is using the family of the ordered weighted averaging (OWA) operator, which considers the risk analysis in the decision-making process [4,8,9]. The OWA family includes a group of operators with several properties. In this family, the most frequently used operators are the OWA, induced ordered weighted averaging (IOWA), and hybrid weighted averaging (HWA). The OWA operator considers only the risk-taking attitudes and disregards the criteria weights. The IOWA operator considers the risk-taking attitudes and the importance orders of criteria, whereas it ignores the criteria weights. The HWA operator considers the risk-taking attitudes and criteria weights, while disregards the stakeholders' power weights [11,12].

In recent years, related to the context of urban water management, several studies have been done based on MCDM methodologies [29–37]. However, in this paper, a risk-based consensus-based GDSS model is developed for IUWM within the study area of an urban watershed. Accordingly, the following improvements are performed in this study that are distinctive comparing to similar works in IUWM:


Accordingly, in order for sustainable water resources management, this research makes the connection between the outputs of watershed modeling and the inputs of a GDSS model for analyzing the risk-based MCDM process. This paper can be used to select the most effective sustainable development criteria of watershed by the stakeholders of the watershed. Additionally, it can assist water scientists and analysts of water resources management to analyze the several impacts of implementing water strategies on the selected sustainable development criteria. Furthermore, it can help all stakeholders to identify the conditions of watershed including several demands, probable water supply resources, and the related impacts on the criteria, which result in better decision making for a sustainable watershed. Ultimately, this study leads to a collaborative group consensus among stakeholders and, consequently, facilitates integrated watershed management.

This paper is organized as follows: Section 2 proposes the flow diagram and explains the complete analysis of the risk-based consensus-based GDSS model for the urban watershed. In addition, this section introduces the study area of the urban watershed, the criteria, the urban water strategies, and the participating stakeholders in the decision-making process. The methodology is also applied for IUWM of the study area. In Section 3, the results, including the scores of urban water strategies, the group consensus measurements, and the final ranking of strategies, are obtained in several risk-taking cases. Section 4 discusses the results and effects of several risk-taking cases on the scores and ranking of the strategies. Finally, Section 5 concludes this paper and proposes future research.

#### **2. Materials and Methods**

#### *2.1. Overview of the Methodology*

In watershed planning and management, especially for IUWM, the stakeholders have several opinions about the importance degrees of sustainable development criteria. Accordingly, the final most effective criteria should be selected based on stakeholders' group consensus. Additionally, the several water strategies, which are classified in three categories of supply management, demand management, and combined supply-demand management, should be evaluated with respect to the selected criteria. The impacts of watershed modeling outputs related to each water strategy on each criterion is considered as the evaluation value of that corresponding strategy with regard to that corresponding criteria. Therefore, the evaluation values of water strategies should enter to the MCDM process of the GDSS model as its inputs for analyzing the model.

In order to analyze the GDSS model based on the risk-taking considerations of the group of stakeholders and group consensus, the risk-based consensus-based GDSS model is developed for urban watershed management in this study. In the risk analysis, a type of OWA operator is proposed to improve the properties of the OWA, IOWA, and HWA operators. Therefore, the stakeholders can evaluate the water strategies with respect to the selected criteria and rank the strategies in each risk-taking attitude of the group. Indeed, each stakeholder and the group of stakeholders can determine that, in each risk-taking case, which water strategy is more desirable and how many criteria are satisfied by that strategy. By using a risk-based weighted Minkowski's method, the stakeholders' group consensus is controlled, and the level of group consensus is determined in each risk-taking case. If the final group agreement is reached, the GDSS process is terminated; otherwise, the threshold level of agreement is reconsidered, or the iterated GDSS process continues based on evaluating other water strategies until the final agreement is achieved.
