Well injection techniques are used where thick, low permeability strata overlie the target aquifers.  Aquifer storage and recovery (ASR) is the direct injection of water by a well for subsurface storage and recovery from the same well. Water storage to bridge seasonal gaps in water supply is often the primary goal with using this technique.  Water treatment is the secondary purpose. It is often practised on brackish/saline aquifers.

Aquifer storage, transfer and recovery (ASTR) describes the injection of water into a well for storage and recovery from a different well. This is often used to achieve additional water treatment in the aquifer by extending the residence time in the aquifer. ASTR can be operated constantly or intermittently, as needed. Direct injection is practiced when groundwater is deep, in terrains with hilly topography, or when existing land use makes surface spreading impractical or too expensive. Examples can be found in North Holland (the Netherlands).