Hydrometeorological Conditions and Sustainable Reservoir Management for Flood Risk Reduction: A Hydraulic Modeling Approach Supporting Climate Action at Colibița Dam, Romania

Dams are critical infrastructures for water supply, flood mitigation, hydropower generation, and sustainable water resources management. However, operational maneuvers and extreme hydrometeorological events may require controlled reservoir releases, which can increase flood risk in downstream communities. In the context of climate change and increasing hydrometeorological variability, sustainable reservoir operation requires an integrated assessment of water availability, flood hazard, and downstream vulnerability. This study investigates the potential flood risk associated with controlled water releases from the Colibița Dam in Romania and their implications for sustainable water resources management and adaptation to climate change. Hydrometeorological data, topographic measurements, dam characteristics, and precipitation data for the period 2001–2024 were considered. A one-dimensional hydraulic model developed in MIKE 11 was used to simulate water releases through the bottom and secondary bottom outlets under low-flow and increased-flow conditions. Three operational scenarios were evaluated: (i) opening each outlet individually at 50% capacity, (ii) opening each outlet individually at 100% capacity, and (iii) simultaneously opening both outlets at 100% capacity. The results indicate that water releases under low-flow conditions generally pose a limited flood risk to downstream areas. The highest flood risk occurs during periods of elevated river discharge when both outlets are operated simultaneously at full capacity, causing the water level at the Bistrița Bârgăului hydrometric station to exceed the danger threshold by 21 cm. At the Bistrița station, the water level exceeds the attention level by 87 cm while remaining 13 cm below the flood level. The findings demonstrate that integrating hydrometeorological forecasts with hydraulic modeling improves adaptive reservoir operation, reduces downstream flood risk, and strengthens resilience to climate-related hazards, thereby supporting Sustainable Development Goal (SDG) 13.1.