Abstract: Geological conditions on the left bank of the Baihetan hydropower station are complicated due to its interlayer dislocation zones, intra-layer dislocation zones, columnar jointed basalt, and other weak geological structures. A large-scale seepage-control and drainage system was arranged in the left bank plant area. Reasonable and effective evaluation of its seepage control effect is of great significance to guiding the safe operation of the station. This paper presents an analysis of the monitoring data from the system and its control effect during the impoundment from April 2021 to March 2022. The results show that the total seepage flow, with a peak of 1249.1 L/min, is significantly affected by the change in the upstream water level, and 69.5% of it is contributed by the seepage through the drainage and irrigation corridors on the third and seventh floors. Pressure head at the anti-seepage curtain rises with the decrease in elevation, with a significant rise at C2. The structural layers C3, C3-1, C2 and LS3152 are more permeable and subjected to larger seepage flows, so that they respond more sharply to the changes in the upstream water level and are prone to seepage channel formation. On the whole, the drainage curtain can effectively reduce the pressure head and maintain the total seepage flow within a reasonable range, achieving a good effect of overall seepage control.

Key words: Baihetan hydropower station, underground powerhouse, seepage law, seepage control effect, leakage channel