reservoir
n. countablen. a large natural or artificial lake used as a source of water supply. It can also mean a large supply of something, like knowledge or energy.
n. a natural or artificial place where water is collected and stored for use, especially for supplying a community or generating power. In a figurative sense, it refers to a large supply or stock of something abstract.
The city gets its drinking water from a nearby reservoir.
After the long drought, the water level in the mountain reservoir dropped to a record low.
The professor is a vast reservoir of historical knowledge, often recalling obscure dates and names without consulting any reference materials.
From French réservoir (“collection place”) (fig.), réservoir (“storehouse”) (lit.). in turn from French réserver (“to reserve, keep”).
Commonly used with the preposition 'of' when referring to abstract supplies, such as a 'reservoir of talent' or 'reservoir of goodwill'.