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Contributions into a river/stream Overland flow – Flow over land surface due to precipitation (runoff) Interflow – Lateral movement of soil water during & immediately after precipitation – Discharges directly into stream Return flow – Flow across land when soil-water throughflow discharges prior to entering stream Baseflow – Discharge from groundwater into stream Direct rainfall
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Hydrograph Analysis
Components of river flowLatrobe River Gauging Station Flows - 226204
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09/11/2004 17/02/2005 28/05/2005 05/09/2005 14/12/2005 24/03/2006 02/07/2006 10/10/2006 18/01/2007 28/04/2007
Date
Flow
(ML/
d)
Contributions into a river/stream• Overland flow
– Flow over land surface due to precipitation (runoff)• Interflow
– Lateral movement of soil water during & immediately after precipitation
– Discharges directly into stream• Return flow
– Flow across land when soil-water throughflow discharges prior to entering stream
• Baseflow– Discharge from groundwater into stream
• Direct rainfall
Baseflow• Streamflow contributed by groundwater• If no rainfall occurs, hydrograph often follows an
exponential decay called a base flow recession• The base flow recession is a function of
topography, drainage pattern, soils and geology
Gaining stream receives groundwater baseflow into the stream
Losing stream leaks surface water into the groundwater storage
Rivers
2
6
4
8
Rain
fall
(mm
)
time
Disc
harg
e m
3 /hr
50
100
Risin
g lim
bFalling limb
Peak discharge
Lag time
Groundwater baseflow
Stormflow
Varying flow conditionsA stream may switch from a gaining stream during low flow conditions to a losing stream during flood conditions
Storm Hydrograph
Storm flow component
Baseflow component
Precipitation component
Bank storage
Bank Storage
Bank storage component is the water entering the stream bank as the stream height rises. As the stream height subsides, the water drains from the bank to be added back to the stream.Is bank storage greater for a stream with steep banks? Or gently sloping banks?
Hydrograph developmentdepends on the:• Rainfall intensity• Infiltration rate• Volume of water infiltrated• Soil moisture deficiency
Environmental flows
End of surface water
Fin
Einde