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Drainage Basin. Mississippi River Basin. Drainage Basin. From Ritter et al., 1995. Interception and Evapotranspiration. Interception: water captured by vegetation and which does not reach the ground.

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Interception and evapotranspiration
Interception and Evapotranspiration

  • Interception: water captured by vegetation and which does not reach the ground.

  • Evapotranspiration: Evaporation (phase change of water from liquid to vapor) + transpiration (water carried from roots to leaves and lost from leaves)

Figure from Chernicoff and Fox, 1997

Flow abstractions


Rainfall intercepted by vegetation before falling to the ground surface

Volume controlled by type, density, and growth stage of vegetation.

Volume decreases with time during the event


Includes both evaporation and Transpiration.

In transpiration, water is moved from the soil, up the plant stem to the leaves, and is lost from the leaves.

Most occurs after the event, rather than during the event.

Flow Abstractions

Flow abstractions1
Flow Abstractions

  • Surface Storage and Detention:

    • Volume of water that fills depressions on ground surface.

    • Does not become part of excess precipitation (direct runoff).

    • Must fill detention storage before runoff can occur.

Dunn and Leopold, 1978


Figure from Chernicoff and Fox, 1997

Flow abstractions2


Movement of water into the subsurface during an event.

Primary abstraction to flow.

Extremely complicated process controlled by multiple parameters.

Parameters controlling infiltration

Physical properties of soil/bedrock.

Nature of vegetation.

Antecedent moisture condition.

Slope of ground surface.

Rainfall characteristics

Flow Abstractions

Elevated Groundwater

Table and Steeper Gradients

Subsurface storm Flow = Elevated G.W.T. + Interflow

Saturated overland flow
Saturated Overland Flow

Saturated Overland Flow = Direct Precip. + Return Flow

From Ritter et al., 1995

Variable source concept
Variable Source Concept

From Ritter et al., 1995

Measurement of stream discharge
Measurement of Stream Discharge

From Ritter et al., 1995

Rating curve
Rating Curve

From Ritter et al., 1995


McCuen, 1989

Hydrograph responses

Flashy: Rapid Response to rainfall event.

Sluggish: Slow response to rainfall event.

Peak Q is usually related to rate of response.

Controlling Factors

Geologic Materials


Basin Morphometry

Basin Size

Basin Shape


Drainage Network characteristics

Hydrograph Responses

Discharge vs basin area
Discharge vs Basin Area

From Ritter et al., 1995

Discharge per unit basin area
Discharge per Unit Basin Area

From Ritter et al., 1995