Groundwater is contained in underground water bodies known as aquifers. We have 32 drinking water supply systems that draw water from aquifers as their primary source of domestic water. Most of these are located in the South East, Eyre Peninsula and Northern region of South Australia. The Blue Lake, which supplies the city of Mount Gambier, is included in this as it is a volcanic crater containing groundwater from local aquifer systems. The quality and volume of water that can be extracted from an aquifer varies from region to region. During 2017–18, 5.4% of the water we supplied was provided by groundwater.