A well screen is an engineered device used in many water wells to help maintain a good water supply from the aquifer and allow for long-term satisfactory operation of the well.
Water wells are constructed in either unconsolidated materials such as sand and gravel or comparatively hard and (usually) stable bedrock. Well screens are installed in wells where the zone containing the water for the well (the aquifer) is comprised of loose or unstable material. The screen prevents rock fragments from entering the well, helps support the wall of the well and allows water to enter.