A huge amount of water exists in the ground below your feet, and people all over the world make great use of it. But it is only found in usable quantities in certain places underground: aquifers. Most of the void spaces in the rocks below the water table are filled with water. These rocks have different porosity and permeability characteristics, which means that water does not move around the same way in all rocks below ground. This web page provides an overview of USGS's research about aquifers and groundwater. It includes related research, publications, news, annd multimedia (Introduction).