The river volume is determined by these four factor mentioned below. There are
1. The size of drainage basin
A larger drainage basin will have a greater volume of water. This is because there is a greater tributaries bringing water to the river resulting in a higher surface runoff.
2. The presence of vegetation
The presence of vegetation affect the rate at which water is intercepted and infiltrate the ground.
If the area is covered with vegetation, less water as in surface runoff and so less volume of the water into the river.
If the area is no vegetation, more surface runoff and increase the volume of the water in the river.
3. Permeability of the rocks
The permeability of rocks is determined by the size of the space or pores between the rock particles in a rock.
If the rock has smaller pores, water cannot easily infiltrate into the rock, the rock is called impermeable. ( high volume of water in the river) e.g granite
If the rock has larger pore , water can easily infiltrate into the rock, the rock is called permeable. ( low volume of water in the river) e.g sandstone.