Why is the water drawn from the bottom of the dam rather than the top?​

Falling water produces hydroelectric power.

Near the bottom of the dam wall there is the water intake. Gravity causes it to fall through the penstock inside the dam. ... The water continues past the propeller through the tailrace into the river past the dam.

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.