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

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

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