Artificial lakes were made in earlier times in order to save ?

Artificial lakes were created in the past to store rainwater. For example, Gadisar Lake is an artificial lake. It is situated in the city of Jaisalmer's southern outskirts. Rainwater gathered in this lake ran for miles. It was designed that any excess water from one lake would flow into a lower-level lake. When that became full, the excess water drained into the next lake. The rainwater might get used all year long. If artificial lakes are not created,  the rainwater runs off and gets wasted. Groundwater, fresh water and drinking water are available only through the rain. Groundwater is available beneath the ground and cannot get stored in artificial lakes. Fresh water and Drinking water will get available only if rainwater is stored in artificial lakes.