Considering the influence of water level fluctuations and the dimensional structure of impermeable walls on the seepage characteristics of embankments, 28 scenarios were designed to compare and analyze the effects of the thickness of impermeable walls, the embedding depth of impermeable walls, and the permeability of the embankment based on the seepage flow, the height of the seepage line behind the membrane, and the hydraulic slope at the bottom and overflow point of impermeable walls under fluctuating water levels. The results indicate that, compared to changes in the thickness of impermea-ble walls, increasing the embedding depth of impermeable walls can more effectively control seepage flow of embankments, reduce the height of the seepage line behind the membrane, and decrease the hydraulic slope at overflow points. For embedding depths ranging from 0 m to 2 m, the hydraulic slope decreases initially with increasing depth, showing a trend of rapid decline followed by a slower decrease. Beyond 2 m, the hydraulic slope increases with depth, reaching its peak at 5 m before sharply declining when exceeding 5 m. Additionally, in suspended-type impermeable wall designs, when controlling the dam base seepage at 75%, the hydraulic slope at the overflow point remains below 0.25. A robust logarithmic-linear relationship exists between the embedding depth of the impermeable wall and the dam base permeability coefficient. The derived fitting equation can be applied for the preliminary design of impermeable wall embedding depth in similar construction projects or for evaluating seepage control in existing projects.