We call them aquifers. Rainwater drains through the soil into the aquifers. We call the water in the aquifer ground water. Groundwater supplies wells and springs. It is a very important source of water for all the plants and animals.
Acid rain soaks into the soil.
Like clean rainwater, it drains down into the aquifer. When it reaches the groundwater, the acid rain pollutes it. It becomes unusable. We have to clean up the air. Two billion people live on our earth.