reservoir

noun

• a large natural or artificial lake used as a source of water supply.
• a supply or source of something:tapping into a universal reservoir of information
• [usually with modifier] a place where fluid collects, especially in rock strata or in the body.
• a receptacle or part of a machine designed to hold fluid.
• Medicine a population, tissue, etc., that is chronically infested with the causative agent of a disease and can act as a source of further infection.