Drought can affect groundwater levels, as shown in this spring

Groundwater, which is found in aquifers below the surface of the earth, is one of the nation's most important natural resources. Groundwater provides drinking water for a large portion of the nation's population, supplies business and industries, and is used extensively for irrigation.

Groundwater can also contribute to surface water supplies. Some groundwater seeps into rivers and lakes, and can flow to the surface as springs.

The water level in an aquifer that supplies water to a well does not always remain the same. Droughts, seasonal variations in precipitation, and pumping affect the height of underground water levels. If a water is pumped at a faster rate than an aquifer is recharged by precipitation or other sources of recharge, water levels can drop. This can happen during drought, due to the extreme deficit of rain.