How does an arch dam transfer water pressure to the sides of a valley?

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dam Itaipú Dam on the Upper Paraná River, north of Ciudad del Este, Paraguay.

An arch dam is a specialized type of dam designed with a curved profile, where the convex side faces upstream. This curvature is fundamental to how the structure manages the immense force of water.

The dam transfers the thrust of the water pressure directly to the valley walls or indirectly through concrete abutments. By utilizing this arch shape, the water pressure actually helps keep the joints in the masonry or concrete closed, enhancing the structural integrity of the dam. Because the dam's strength is entirely dependent on this lateral support, it is essential that the valley sides consist of sound rock to provide the necessary abutment stability.1