Lakes and dry creek beds may fill up with water during heavy rains. If the water table is low in underlying aquifers, water may seep from the sides of these water bodies and percolate into the groundwater. In some places, artificial recharge is used to replenish aquifers. This is accomplished through the pumping, or injection, of water into wells where it replenishes the aquifer directly or through the spreading of water over the land surface where it can seep into the ground. Artificial recharge is done to replenish the groundwater supply when rains are heavy in order to preserve water for later use or, in the case of injection wells, to dilute or control the flow of contaminated groundwater.
Gravity is the dominant driving force in groundwater movement in unconfined aquifers.
Groundwater can also leave the aquifer via the pumping of a well. The process of groundwater outflowing into a surface water body or leaving the aquifer through pumping is called discharge. Many rivers, lakes, and wetlands rely heavily on groundwater discharge as a source of water. During times of low precipitation, these bodies of water would not contain any water at all if it were not for groundwater discharge. It is important to note that because of discharge, contaminants in groundwater can flow into surface water bodies.