How can furtilizer pollute water?

Answer 1

Fertilizer contains various chemicals which enter the soil, and are slowly washed downward until they enter an aquifer, spring, or underground river. This water is likely to eventually end up in a reservoir, river, or well. Now the unlucky person who's water supply it has entered get the privilege of drinking the fertilizer you put on your lawn. Also, there is phosphorus in fertilizer which will encourage the growth of Algae in whatever water source it ends up in.