Rivers, streams and creeks are a surface water system with a
network of channels that collect and move runoff. Runoff is
excess water that is not adsorbed by the surrounding area. Runoff can be
created by rainfall, melting snow, or groundwater discharge. The shape
of the river system will depend on the topography, the type of rock or
soil it is traveling through, and the style of its biological diversity.
For instance, pine trees require a lot of water to grow. Runoff in a
pine tree forest would be less than if the area was populated by oak
trees. Oak trees require less water than pine, so more water would be
available as runoff.