For example ground water helps our water supply by cleaning the water and by storing it for us. Megan I learned that ground water is the water we drink. It is pumped from the ground. Pipes are in the ground. Pipes go all the way down to where the water is in the ground.
Water is very far into the ground.
If oil or any other bacteria are spilled into the ground they will reach the clean water and fill it with bacteria. Then it will get pumped out and you could drink it. Even babies younger than six months could get very sick. For an example if you take a jar that was 12 inches and fill it with water and put 2 drops of oil in it it would turn that water into waste water. We did a ground water experiment.