Reservoirs are lakes where water is stored.
Reservoirs can be formed by building a dam across a flowing river.
Water from reservoirs can be used by people for watering crops or for drinking and bathing.
If a reservoir is large enough, it may also be used for water sports.
Some reservoirs can be used to create electricity by allowing the water to flow out through special machines.
The biggest reservoir in the world is in Africa. It is called Lake Kariba.