Groundwater storage systems include methods and technologies used to store and manage water below the surface of the earth. These systems can be used for a variety of purposes, including storing drinking water, agricultural water, rainwater, and even thermal energy. These tanks can be made of polyethylene, concrete or other materials and are used to store water below ground level. Polyethylene tanks are popular due to their corrosion resistance, long life and ease of installation. Artificial groundwater recharge: this method involves directing water into groundwater aquifers to increase water storage and prevent land subsidence. There are several methods for artificial recharge, including ponds, wells and direct injection of water into aquifers. Thermal energy storage systems: In these systems, hot or cold water is stored underground to be used when needed. These systems can help improve the energy efficiency of buildings. Rainwater storage systems: These systems store rainwater collected from roofs or other surfaces underground to be used when needed. The use of underground rainwater storage modules, especially in urban areas, can provide benefits such as increased storage.