Question

How is a reservoir of groundwater formed

Answer 1

"The depth at which soil pore spaces or
fractures and voids in rock become
completely saturated with water is
called the water table. Groundwater is
recharged from and eventually flows to
the surface naturally; natural discharge
often occurs at springs and seeps, and
can form oases or wetlands."........

Answer 2

Valley-dammed reservoirs are created in valleys between mountains. Usually, there is an existing lake or body of water. ... To create a valley-dammed reservoir, the river that will fill the reservoir must be diverted, so the ground can be cleared to lay a foundation for the dam.