The Hydrological (Water) Cycle and Drainage Basin Systems Practice Test

Water running over the land surface during or after rain is called surface runoff. It happens when rainfall arrives faster than the soil can absorb it or when the soil is already saturated, so water flows as sheet flow across the ground and can form tiny channels that carry it toward lower areas and into streams. This surface movement is different from channel flow, which is water moving inside established stream channels after water has collected and concentrated. Condensation is the process of water vapor turning into liquid in the air or on surfaces, and precipitation is water that falls from the sky as rain, snow, etc. Neither of those describes water moving across the land surface after a rain event.