Runoff and Hydrographs MCQ with answer and solution

Concept

Baseflow is the portion of streamflow that comes from subsurface storage (groundwater or interflow) rather than direct surface runoff.

Step-by-step solution

1. Understand the components of a hydrograph: Surface runoff (direct runoff) and baseflow. 2. Surface runoff represents the rapid response of a watershed to precipitation. 3. Baseflow represents the slow, delayed contribution from groundwater and subsurface sources. 4. Therefore, subsurface flow into a stream is termed baseflow.

Explanation

Baseflow refers to the delayed subsurface flow that enters a stream channel, sustaining its flow during dry periods between rainfall events. It is primarily fed by groundwater seepage into the stream.

Why the other options are wrong

A: Surface runoff is direct runoff from precipitation that reaches the stream quickly. B: Return flow typically refers to water that is diverted from a source and returned to the same or another source, often in irrigation. D: Rainfall excess is the amount of rainfall that directly contributes to surface runoff after accounting for initial losses and infiltration.

Shortcut

Baseflow = Groundwater contribution / delayed flow to the stream.

Common mistake

Confusing baseflow with surface runoff or rainfall excess.