The adaptive operation of hydropower plants has become essential in response to the increasing frequency of extreme climate events. This study evaluated the performance of the Americana Small Hydropower Plant (SHPP), located in the Piracicaba, Capivari, and Jundiaí (PCJ) river basin, under two operational strategies: the current rule and a new one allowing reservoir drawdown of up to 1.5 m. The results showed significant gains, a 29% increase in average annual generation, an increase in generation days from 45% to 79%, and a reduction in spill days from 56% to 21%. Additionally, the new operational rule maintained minimum outflows above 15 m3/s for 79% of the time, promoting greater downstream hydrological stability and mitigating environmental impacts such as water quality degradation. The frequency of flows equal to or greater than 15 m3/s also increased by 34%, contributing to higher downstream flows during dry periods. During heavy rainfall events, the strategy enabled the attenuation of peak flows, helping to reduce urban flooding risks. These findings demonstrate that operational flexibility enhances the plant’s ability to adapt to extreme climate conditions and optimizes hydropower scheduling and adaptation strategies in the context of climate change.