Underground water reservoirs, also known as aquifers, are natural formations that store water beneath the Earth's surface. They are typically made up of porous rock or sediment that can hold significant amounts of water. These reservoirs are crucial for supplying fresh water for drinking, irrigation, and industrial use. Aquifers recharge through rainfall and surface water that seeps into the ground. The water in these underground reservoirs can be accessed through wells and springs. Proper management of aquifers is essential to prevent over-extraction and contamination, ensuring a sustainable water supply for future generations.