STRUCTURES like dams and man-made dikes widen at the base. in terms of water presure, explain this design.

Question

STRUCTURES like dams and man-made dikes widen at the base. in terms of water presure, explain this design.

Answer 1

Basically, whenever there is a body of water, the pressure at the bottom of the pool will be greater than the pressure taken anywhere else in the pool because gravity is "pulling" more water down toward that area.  As you head upward from the bottom of the pool, the pressure will decrease because the amount of water above starts decreasing.  This decrease in water is "less heavier", or in other words, has less pressure.

This being said, in order to retain a body of water, the base must be wide enough to hold back the great amount of water pressure.  

In addition, even the curvature of the dam can help retain the water behind the dam.  (Just like how arc bridges sustain weight)

If you look at the blueprint of any major dam that holds back a lot of water, you can see how thick the base of the dam is.  It's really amazing.

=)

Answer 2

The higher the water level against a dam wall, the greater is the pressure exerted on the wall by the water, the least being at the surface, the greatest being at the deepest point. Thus the structure needs to be stronger in the lower parts. If you were to consider a vertical column of water (regardless of the shape of the column), and you measure the pressure difference between near the surface and that at the base of the column, the base will be considerably greater pressure due to the "weight" of the water above it.