Throughout history, civilizations have improved water supply and management systems depending on new needs and innovations. Anatolia, home to many civilizations, showcases the development of water systems from the Neolithic period to the present. Beypazarı, located in Central Anatolia, demonstrates an advanced Ottoman-era water supply system with 19th and 20th-century water structures, such as fountains and riverbeds, despite many drying up today. However, infrastructure works have disrupted connections between water sources, fountains, and agricultural lands. Fountains have lost their function due to river drying, global warming, and man-made interventions. This study aims to understand Beypazarı's historical water supply system between the 19th and 20th centuries and the effect of interventions on increasing floods. Visible components, including natural water sources and fountains, were analyzed through site surveys, literature data, and unstructured interviews with locals. Lost components were examined using locals' narratives, old cadastral maps, and aerial photos. The whole system was determined by overlapping data and land slope using GIS. Results show that Beypazarı's historic water supply system during the Ottoman period was tailored to the purpose of water usage. Specific stream branches and springs provided drinking water, transported to fountain reservoirs via a closed pipe system for hygiene. All stream branches were distributed to agricultural lands through open runnels using gravity. The abandonment of this system has caused stream beds to exceed their capacity in winter, leading to floods.