A reservoir is a large natural or artificial lake used to store water. It collects water from rivers, rain, or melting snow, ensuring a steady supply for drinking, irrigation, and recreation. Reservoirs play a crucial role in managing water resources, especially in areas prone to drought. Many reservoirs are created by building a dam across a river, which holds back the water. This stored water can also be used to generate electricity through hydroelectric power, benefiting communities and industries. Examples of famous reservoirs include the Hoover Dam and the Lake Mead in the United States.