What is the purpose of a cistern?

A cistern is a waterproof receptacle designed for storing water, typically rainwater or groundwater. Its primary purpose is to collect and hold water for domestic, agricultural, or industrial use, especially in areas where water is scarce. Cisterns help in managing water resources efficiently, promoting water conservation, and providing a reliable supply during dry periods. Additionally, they can aid in reducing runoff and erosion by capturing excess rainwater.