Where are they located in the deserts: rivers, water?

Deserts are deserts because there are not enough rivers and water for normal existence. There are very few of them.
In deserts, rivers are located deep underground. That is, in the deserts there are practically no rivers we are used to, as they dry up under the sun.
If there are land rivers, then they originate outside the desert (for example, the Nile, Colorado) and are full-flowing, which does not allow them to dry out.
Desert water is found in oases as well as underground.