## 2 State of the Art  
Since the management of water resources also involves intangible components, such as strategic profiles, socio-political conditioning and ethical/moral considerations of an intangible asset such as water, for the characterization of the model, we decided to use the analytic hierarchy process (AHP), a method extensively structured in the literature. This section examines the main examples of the application of a multiple-criteria decision analysis (MCDA) in the field of water resources management found in the literature. We focus above all on the AHP, a technique that allows for addressing complex issues in the field of water resources management, offering valid support to the decision-making process. Thanks to the use of a hierarchy of criteria and the definition of relative weights, the AHP allows one to carry out objective assessments and identify effective solutions for the sustainable management of water resources [21]. The most commonly applied methods for planning and managing water resources are the fuzzy set analysis, compromise programming (CP), the analytic hierarchy process (AHP), ELECTRE and PROMETHEE [22]. Some of the main application cases developed in the last twenty years are detailed below. The first study analyzed in this section presents a multi-criteria decision support methodology for the selection of projects to be included in the annual rehabilitation programs of drinking water networks in the European context [23]. To select the best wastewater treatment alternative, another study proposes a multi-criteria analysis methodology using both the analytic hierarchy process (AHP) and gray relational analysis (GRA). The AHP is used to manage multiple criteria and objectives during the decision-making process, while the GRA focuses on analyzing uncertain relationships between a major factor and all other factors in a system [24]. A third example proposes a multi-criteria decision analysis (MCDA) based on the analytic hierarchy process (AHP) within the framework of the IWRM in Bolivia to support stakeholders in the sustainable management of water resources [25]. Another research study uses a combination of methods, including a system dynamics study (SD) and the analytical hierarchy process (AHP), to create a rating index system and model for the ecological carrying capacity of water in a region [26]. A subsequent study presents a conceptual model of a three-phase strategic approach (3-SSA) for integrated water resources management, focusing on the first phase of minimization and the prevention of contamination at the source. A case study is presented in the expansion area of the city of Cali, Colombia, to evaluate different alternatives through a multi-criteria analysis [27]. Another study proposes the combined use of SD, the AHP and the creation of an integrated decision support system (DSS) for the sustainable management of water resources [28]. Other researchers have evaluated the water security of the Yellow River by integrating the fuzzy analytical hierarchy process (FAHP) with various other models (SPA, TOPSIS, GRA, VS and ME) [29]. Another example presents a multi-criteria analysis tool (MCA) to evaluate water resource management (WRM) strategies and select the most appropriate ones using four techniques (MAUT, AHP, ELECTRE and TOPSIS) [30]. In a recent work, a model was introduced to develop a multi-criteria spatial decision support system, which was designed to assist decision makers in defining and analyzing the investment priorities of individual water utilities [31]. Moreoever, recently, a decision support system was developed for emergency managers, to identify and rank the best options for water supply in crises. The approach used, based on the AHP, made it possible to integrate scientific and specialist knowledge into the decision-making process and to include criteria that are often overlooked in other methods and tools, such as social impacts [32].