Why the supporting wall of dam are board at the bottom?

The supporting walls of a dam are broader at the bottom to provide greater stability and resist the immense hydrostatic pressure exerted by the water. This design helps distribute the weight of the water more evenly and prevents the wall from toppling over or sliding. Additionally, a wider base increases the dam's resistance to erosion and improves its overall structural integrity. This shape also allows for better anchoring into the ground, ensuring the dam remains secure under varying water levels.