Groundwater supplies drinking water for 51% of the total U.S. population and 99% of the rural population. Groundwater helps grow our food. Groundwater is an important component in many industrial processes. Groundwater is a source of recharge for lakes, rivers, and wetlands.

A water well system next to a house, showing how aquifers are an important source of water. An aquifer is a body of rock and/or sediment that holds groundwater. Groundwater is the word used to describe precipitation that has infiltrated the soil beyond the surface and collected in empty spaces underground.

Protecting aquifers is important. The water supply gets polluted when contaminants — like chemicals or manure — seep into groundwater. The quantity of groundwater needs protection too. Groundwater levels can decline if too much water is pumped from an aquifer.

Most of the time, U.S. groundwater is safe to use. However, groundwater sources can become contaminated with germs, such as bacteria, viruses, and parasites, and chemicals, such as those used in fertilizers and pesticides. Contaminated groundwater can make people sick. Water infrastructure requires regular maintenance.

The time it takes for surface infiltration to reach an aquifer as deep as 400 feet may take hours, days, or even years, depending on the rate of recharge. In some of the flood-irrigated areas, groundwater levels in nearby domestic wells rise within a few hours to days of flood-up.

Most aquifers are naturally recharged by rainfall or other surface water that infiltrates into the ground. However, in regions where groundwater use is greater than natural recharge rates, aquifers will be depleted over time.

Groundwater supplies are replenished, or recharged, by rain and snow melt that seeps down into the cracks and crevices beneath the land’s surface. In some areas of the world, people face serious water shortages because groundwater is used faster than it is naturally replenished.

Rainwater, or snow melt, either soaks into the ground to become groundwater, evaporates, or flows over the surface of the land. The water that flows over the ground is called stormwater or runoff.

The hole in the ground collected the water that fell and the grass grew into a brighter green around its edges.

1/2 (0.5) of an inch of rain – A light rain never reaches this amount, moderate rain for 1-2 hours or heavy rain for 30-45 minutes. One (1.00) inch of rain – A light moderate rain never reaches this amount, heavy rain for several hours (2-5 hours). There would be deep standing water for long periods of time.