There are three types of river regime:-
1. Ephemeral Rivers
2. Intermittent Rivers
3. Perennial Rivers
1. Ephemeral Rivers:
Ephemeral rivers are characterized by the temporary quick flow as a result of exceptionally heavy downpours or rapid melting of snow. The bed of these rivers remains dry for most of the year since water table is far below the surface and the base flow does not occur.
Such rivers are found as wadis of the desert areas. In desert areas flash flooding occurs on the most irregular basis.
2. Intermittent Rivers:
Intermittent rivers are of semi-permanent nature. They are characterized by seasonal flow. Such rivers flow during wet periods when runoff is related to both quick flow from the heavy rain and/or base flow from a temporary rise of water table to the level of the river bed.
During the summer, which is the dry period, the river bed is normally dry due to reduced rainfall and falling water table.
3. Permanent Rivers:
Permanent rivers are characterized by continuous flow since water table is always at the level of the river channel. Such rivers have a constant base flow at all times. Besides, they are supplemented by quick flow as a result of heavy rainstorms.
However, the majority of rivers represent a combination of two or three types of flow along some parts of their course.