A reservoir is a large natural or artificial lake used to store water. It is created by constructing a dam across a river or stream, which allows water to accumulate behind it. Reservoirs are essential for various purposes, including supplying drinking water, irrigation for agriculture, and generating hydroelectric power. In addition to their practical uses, reservoirs also play a role in flood control by managing excess water during heavy rainfall. They can support local ecosystems by providing habitats for fish and wildlife. Overall, reservoirs are vital components of water management systems in many regions around the world.