reservoir

n. large lake for storing water; container used to collect and store water; additional supply, reserve; area or location where something is stored (esp. liquid)

Most often, a reservoir refers to an artificial lake, used to store water for various uses. Reservoirs are created first by building a sturdy dam, usually out of cement, earth, rock, or a mixture. Once the dam is completed, a stream is allowed to flow behind it and eventually fill it to capacity. Reservoirs exist in a wide variety of shapes and sizes, and can be either natural or man-made.
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Noun
1. a large or extra supply of something; "a reservoir of talent"
(hypernym) supply
2. lake used to store water for community use
(synonym) artificial lake
(hypernym) lake
(hyponym) Lake Mead
(part-holonym) water system, water supply, water
3. tank used for collecting and storing a liquid (as water or oil)
(hypernym) tank, storage tank
(hyponym) cistern
4. anything (a person or animal or plant or substance) in which an infectious agent normally lives and multiplies; "an infectious agent depends on a reservoir for its survival"
(synonym) source
(hypernym) thing

n. reservoir, reserve, large lake for storing water; container used to collect and store water; area or location where something is stored (esp. liquid)

n. tank, reservoir, cistern