The phrase "main reservoir" refers to a large storage area or container that holds a significant amount of something, like water, fuel, or energy, which can be used as a source or supply for various purposes. Full definition
Conversely, while the number of comets known today totals just a few thousand, they originate in two main reservoirs containing up to a trillion such objects, namely the Kuiper Belt in the ecliptic beyond Neptune and the Oort Cloud, uniformly distributed around the solar system at large distances, perhaps stretching halfway to our nearest stellar neighbours. (summerschoolalpbach.at)
The water utility serving New York City has identified heavy precipitation events as one of its major climate - change - related concerns because such events can raise turbidity levels in some of the city's main reservoirs up to 100 times the legal limit for source quality at the utility's intake, requiring substantial additional treatment and monitoring costs (Miller and Yates, 2006). (ipcc.ch)
The disease enters herds through the shipping of undiagnosed cattle, and from badgers, which are the main reservoir of the disease in wildlife. (sciencemag.org)