A high arch dam is located in an alpine valley with complex hydrogeological conditions. After impoundment

significant seepage has occurred in multiple drainage holes of the drainage tunnel of dam foundation on the left bank

which is a key concern of the project. To identify the cause of the seepage

 based on the hydrogeological conditions during impoundment

seepage control and treatment measures

 pseudo-random flow field method detection results

monitoring and inspection results

combined with nearly 10-year monitoring data under the 80 m cycle of reservoir water level fluctuation

a comprehensive analysis is conducted on the characteristics of seepage and seepage pressure in the drainage tunnel and behind the curtain

as well as the source of seepage. The results indicate that the curtain in dam foundation of the left bank is effective

the seepage and seepage pressure have decreased year by year and tend to stabilize

and the seepage volume is much smaller than the design pumping and drainage capacity of the dam foundation drainage well. The seepage mainly comes from mountain groundwater and downstream river water

and the seepage is safe and controllable.