###### Abstract  
Access to safe and reliable water is a fundamental requirement for sustainable urban development. However, water distribution systems (WDSs), particularly in small and aging municipalities, face persistent challenges, including infrastructure degradation, population growth, and limited operational data. This study presents a comprehensive hydraulic modeling framework for the city of Farsala, Central Greece, an area characterized by significant data scarcity and outdated water network records. A novel methodology was developed that combines AutoCAD-based network digitization, GIS data integration, field surveys, and real-time SCADA telemetry to create a high-fidelity and operational hydraulic model using WaterGEMS software. The model was calibrated and validated using observed pressure and flow data, achieving high performance metrics, including a Nash-Sutcliffe efficiency (NSE) of 0.841 and R\({}^{2}\) of 0.90. Extended period simulations (EPS) were conducted to evaluate system behavior over a 24 h cycle, revealing critical insights into pressure distribution, peak demand conditions, and leakage hotspots. The results demonstrate that even under constrained data conditions, it is possible to construct a robust and decision-supportive model, offering valuable guidance for future system upgrades, leakage control strategies, and smart infrastructure planning in similar urban environments. water distribution system; hydraulic modeling; simulation; GIS; WaterGEMS; SCADA; telemetry 2025  
24 April 20  
The primary objective of a WDS is to provide water to private dwellings, industrial facilities, and public spaces in an adequate amount with a suitable pressure level without compromising its quality [6]. This is a particularly complex task, as WDS must continuously adapt to varying conditions arising from multiple factors, including daily and seasonal fluctuations in demand, emergency requirements such as fire protection, population growth, urban expansion, climate change and variability, as well as evolving socio-economic conditions [7]. Through the rapid development of computational tools, the need for hydraulic simulation in water supply networks has grown significantly [8]. Modern aqueduct simulations enable real-time operational adjustments, infrastructure optimization, and informed decision-making, allowing engineers to predict network behavior under various conditions [9]. [PERSON] (2021) emphasized the identification of critical pipes for rehabilitation, introducing a risk-based prioritization approach that underscores the need for proactive infrastructure maintenance [10]. However, it leans heavily on structural vulnerability and may underrepresent dynamic hydraulic performance. In contrast, [PERSON] et al. (2022) and [PERSON] et al. (2022) focused on leakage detection, employing comparative pressure analysis and sensitivity modeling, respectively. [PERSON]'s approach is notable for integrating observed SCADA data with simulations, enhancing the realism of leak localization, while [PERSON]'s study added empirical verification and examines the nonlinear behavior of leaks under varying pressures [11; 12]. On the design side, [PERSON] and [PERSON] (2015) and [PERSON] et al. (2023) compared the LOOP and WaterGEMS tools, demonstrating that WaterGEMS provides superior pressure control and demand forecasting, making it preferable for large-scale urban networks [13; 14]. [PERSON] and [PERSON] (2016) advanced pressure-driven modeling within EPANET, a crucial enhancement for accurately simulating low-pressure scenarios, yet the practical applicability is constrained by computational demands [15]. Similarly, [PERSON] et al. (2022) addressed simulation anomalies related to zero flows in low-resistance networks using the Global Gradient Algorithm, contributing to model stability but lacking broader operational context [16]. [PERSON] et al.