Abstract: In recent years, incidents of damage to high dam discharge structures have become increasingly frequent. The Three Gorges Dam, boasting the world’s highest discharge volume and falling head, commands unparalleled discharge power, making its discharge safety a matter of great concern. Drawing upon hydraulic prototype observations and model tests conducted since its impoundment in 2003, we examine seven pivotal factors affecting discharge safety: discharge structure layout, discharge capacity, dynamic pressure, flow cavitation, aeration, ventilation wind speed, cavitation wear, as well as energy dissipation and erosion prevention. In accordance with relevant technical standards and engineering experiences, we propose a comprehensive method for evaluating flood discharge safety tailored to high dams, outlining both qualitative criteria and quantitative thresholds. Our findings demonstrate the rationality of discharge structures of the Three Gorges Dam. The actual discharge aligns well with design values. The spillway structure sees no cavitation wear. In conclusion, over the two decades of operation, the drainage structures and energy dissipation zones of the Three Gorges Dam have operated reliably, ensuring the safety and efficacy of flood discharge operations.

Key words: flood discharge safety, spillway structures, discharge capacity, water flow aeration, cavitation wear, energy dissipation and erosion prevention, Three Gorges Dam