High and low tides are caused by the moon. The moon's gravitational pull generates something called the tidal force. The tidal force causes Earth—and its water—to bulge out on the side closest to the moon and the side farthest from the moon. These bulges of water are high tides.
A spring forms where the water table intersects the ground surface. Sometimes, the ground surface is lower than the water table. This forms a natural water flow as a spring.
An artesian well occurs where pressurized formations containing ground water is found.
Unsaturated zone is not filled with ground water.
An aquifer is a porous and permeable formation that can store ground water
