<p>Reliability, as well as life cycle management of the dam-based electricity generation plants are The reliability and life cycle management of equipment used in dam-based electricity generation plants is critical for their effective and sustainable functioning, as unexpected equipment failures will lead to operational downtime that adversely affects the power generation available from these assets whereas planned maintenance is expected to be conducted at a lower cost than ad-hoc repairs. This paper presents an integrated framework for improving operational performance and minimizing downtime through the application of reliability engineering principles along with Lean Six Sigma methodologies. Reliability metrics including mean time between failures (MTBF) and mean time to repair (MTTR) were used to assess system performance. The collected operational and maintenance data over a four-month period. Further, to identify and prioritize the critical failure modes, they used failure mode and effects analysis (FMEA) and risk priority number (RPN) techniques—and then employed DMAIC &amp; root cause analysis to objectively develop a specific plan for improvement. Five of these total downtimes identified 24.5 h (MTBF = 14.88 days, MTTR = 3.06 h). The implementation of the proposed framework achieved 30% reduction in unplanned downtime and an estimated increase of 15%, for electricity generation, by improving maintenance effectiveness and operational reliability. The results demonstrate that the reliability engineering combined with Lean Six Sigma is a structured and data-driven methodology that can be effectively utilized to not only improve maintenance performance, reduce operational disruptions but also to ensure that electricity generation plants by way of dams are sustainable in the long run.</p>