drainage basin. mississippi river basin drainage basin
TRANSCRIPT
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
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
Saturated Overland Flow
Saturated Overland Flow = Direct Precip. + Return Flow
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 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