## 1 Introduction  
In recent years, the issue of the impact of climate change on water security has become an important topic [1; 2; 3; 4]. The great variability in natural water supply and water demand results in serious problems for engineers [5]. In the planning process for adapting or adjusting to the actual and expected climate and its effects, climate-related vulnerabilities and risk assessments are important. Such assessments are designed to identify adaptation options and measures. These approaches are generally classified into two groups: top-down modeling assessments and bottom-up threshold analyses [6]. To date, most top-down scenario-led impact assessments have been applied to select optimal solutions [7]. These approaches are based on climate projections and GCM downscaling to predict the impacts of climate change. These methods have proven to have little practical use in site-specific water resource management and water infrastructure project design decisions at the local level [8]. In contrast to the top-down approach, bottom-up climate assessments begin in the vulnerability domain and assess particular climate impacts using the best available or prescribed climate information [8]. Such approaches do not consider climate projections and are intended to assess the current sensitivity and vulnerability of a water resource system as a basis for water structure and system vulnerability. The bottom-up approach generally seeks robust strategies that perform reasonably well in a wide range of uncertain future scenarios. This approach was used in this study. These approaches relate to the vulnerability framework proposed by the Intergovernmental Panel on Climate Change (IPCC). To date, two frameworks have been proposed, the first in the _Fourth Assessment Report_ (IPCC 2007) [9] and the second in the _Fifth Assessment Report_ (AR5) (IPCC 2014) (Figure 1) [10]. In the IPPC 2007 framework, vulnerability is conceived as a function of exposure, sensitivity, and adaptive capacity, while IPPC 2014 separates exposure from vulnerability, and vulnerability is therefore a function of sensitivity and the capacity to cope and adapt. Both frameworks have been widely used, depending on the risk assessment context and approach [11]. The top-down method projects future climate conditions specific to the watershed of concern, i.e., assessed exposure: \"The nature and degree to which system is exposed to significant climate variations\" [12]. Precipitation feed-in system Global Climate Models (GCMs) frequently provide streamflow outputs, enabling the assessment of the performance of water-supply systems in a changing climate [13; 14; 15]. This is a top-down, data-driven approach to the concept of vulnerability presented in the IPCC report (2007) (Figure 1a). Different approaches and methods have been used, including the scenario approach, climate sensitivity methods, paleoclimate studies, historic climate observations, and theoretical models (hydrothermal-coupled equilibrium) [6]. These approaches are computationally and resource-intensive. In addition, the transformation of climate data into long sequences of runoff data and data on possible variations in runoff resulting from climate change is not possible. Therefore, the statistical distribution of future conditions is unknown or cannot be trusted. Therefore, it is necessary to apply a simplified and robust approach. This enables a bottom-up approach that generally favors robustness over optimality. This approach was used in this study. The bottom-up approach generally integrates methods for climate risk assessment and robust decision analysis with risk management procedures. The procedure is flexible and adapts to a local problem-solving framework and the available information and knowledge. In this approach, climate change vulnerability assessments are based on the knowledge of the system itself (water resource systems, water abstraction facilities, and utilities).