Design for resilient performance of hydraulic structure

Hydropower is the most efficient form of renewable energy that harnesses the power of flowing water to generate electricity. It is a clean, reliable, and sustainable source of long-lasting electricity generation. It is considered one of the most widely used and reliable renewable energy sources globally with the smallest amount of greenhouse gas emissions. Many countries count on hydropower to meet their electricity demand, contributing to energy security and reduced dependence on fossil fuels. Hydropower is a significant source of renewable energy in Bhutan, and hydraulic spillway facilities play a crucial role in ensuring the safety and efficient operation of these power plants. Investigating the design and performance of these spillway facilities is crucial for increasing their service life and reducing repair maintenance costs. Understanding the factors influencing their performance is essential for designing and rehabilitating hydraulic structures. The investigation was carried out to examine the design and performance of the hydraulic spillway facilities at the Kurichhu Hydropower Plant in Bhutan, focusing on parameters such as Froude number, conjugate depths, and the level of conjugate depth. The investigation involves data collection and analysis of flood events. Gumbel's method is used for flood frequency analysis to obtain peak flood discharge corresponding to different return periods based on recent inflow data sets. Additionally, calculations are conducted to determine the necessary gate openings at various discharges to maintain the constant upstream water surface elevation at the full reservoir level. With this, the flow velocity required to protect the spillway facilities from damage during multi-gate operations is determined. The study reveals that the height of the gate opening mainly influences the flow velocity, and the number of gate openings influences the amount of discharge. Small opening gate height was found with high crest velocity due to a higher pressure head difference. Moreover, the evaluation of hydraulic parameters indicated that the chosen spillway design and stilling basin geometry are adequate to guarantee a long-lasting safe structural performance with some rehabilitation. The additional concrete strengthening construction materials and modification in hydraulic structure i.e. a baffle wall and chute are suggested to improve the performance of the spillway and stilling basin.