Drainage Basin. Mississippi River Basin Drainage Basin.

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.

• 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

• Interception– 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

• Evapotranspiration:– 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

• 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

Infiltration

Figure from Chernicoff and Fox, 1997

Flow Abstractions

• Infiltration– 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

From Ritter et al., 1995

From Ritter et al., 1995

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

Elevated GroundwaterTable and Steeper Gradients

Saturated Overland Flow

Saturated Overland Flow = Direct Precip. + Return Flow

From Ritter et al., 1995

Variable Source Concept

From Ritter et al., 1995

Measurement of Stream Discharge

From Ritter et al., 1995

Rating Curve

From Ritter et al., 1995

Richland Creek Stage Data

0

100

200

300

400

500

600

9:00

0:15

15:1

5

6:30

21:4

5

13:0

0

4:15

19:3

0

10:4

5

2:00

17:1

5

8:30

23:4

5

15:0

0

6:15

21:3

0

12:4

5

4:00

Time

Sta

ge

Hydrograph

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

– Vegetation/Land-use

– Basin Morphometry• Basin Size• Basin Shape• Relief • Drainage Network

characteristics

Discharge vs Basin Area

From Ritter et al., 1995

Discharge per Unit Basin Area

From Ritter et al., 1995

From Ritter et al., 1995