river flow regimes and effective discharge · effective discharge functional-equivalent discharge q...
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![Page 1: River flow regimes and effective discharge · EFFECTIVE DISCHARGE FUNCTIONAL-EQUIVALENT DISCHARGE q f [Doyle and Shields, 2008]: the constant value of discharge resulting in the same](https://reader034.vdocuments.net/reader034/viewer/2022042803/5f4b95112be844378972e3ac/html5/thumbnails/1.jpg)
Eawag: Swiss Federal Institute of Aquatic Science and Technology
Stefano Basso | Riccardo Sprocati Alessandro Frascati | Marco Marani
Mario Schirmer | Gianluca Botter
River flow regimes and effective discharge
Photo: FOEN
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EFFECTIVE DISCHARGE
FUNCTIONAL-EQUIVALENT DISCHARGE qf [Doyle and Shields, 2008]: the constant value of discharge resulting in the
same amount of sediment transport determined by the overall hydrologic regime over long time scales.
Sediment rating curve
Photo: Anja Bretzler
TIME
WA
TE
R
FL
OW
q
S
ED
IME
NT
F
LO
W
qs
SE
DIM
EN
T
FL
OW
q
s
WATER FLOW q
qqs
Time series of sediment and water flows
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EFFECTIVE DISCHARGE
FUNCTIONAL-EQUIVALENT DISCHARGE qf [Doyle and Shields, 2008]: the constant value of discharge resulting in the
same amount of sediment transport determined by the overall hydrologic regime over long time scales.
Sediment rating curve
Photo: Anja Bretzler S
ED
IME
NT
FL
OW
qs
WATER FLOW q
fsssss qdqqpqq
0
)(
Average sediment flow due to the underlying flow regime
qf
sq
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EFFECTIVE DISCHARGE
FUNCTIONAL-EQUIVALENT DISCHARGE qf [Doyle and Shields, 2008]: the constant value of discharge resulting in the
same amount of sediment transport determined by the overall hydrologic regime over long time scales.
Photo: Anja Bretzler
What is it used for?
Lifespan of reservoirs
Channels design / river restoration
Models studying long-term evolution of rivers
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OBSERVED EFFECTIVE DISCHARGE
18 catchments 4 seasons
Water & suspended sediment flow data
Every river shows a different value.
Why? Climate, basin morphology, sediment features, flow variability, …
How do these factors interact?
EF
FE
CT
IVE
DIS
CH
AR
GE
(P
ER
UN
IT C
AT
CH
ME
NT
AR
EA
) [c
m/d
]
CATCHMENT #
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WORKING HYPOTHESIS
COEFFICIENT of VARIATION
of DAILY FLOWS CVq
FUNCTIONAL-EQUIVALENT RATIO (EFFECTIVE RATIO)
q
qR
f
f
The river flow regime
is a key driver of the
effective discharge
EF
FE
CT
IVE
RA
TIO
R
f [
-]
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[Botter et al., WRR 2007, 2008]
CLASSIFICATION of NATURAL FLOW REGIMES
= frequency of effective rainfall; = hydrograph recession rate k
kCVq
[Botter et al., PNAS 2013]
Streamflow pdf ~
River flow regime
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Effective ratio
Effective discharge
Sediment flow pdf
Streamflow pdf
Sediment rating curve
[Basso et al., GRL 2015]
AN EXPLANATORY FRAMEWORK
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AN EXPLANATORY FRAMEWORK
k
Function of the flow regime
(persistent/erratic)
1
k
kk
q
qR
f
f
Climatic control (effective rainfall frequency)
Landscape control (hydrograph recession rate)
PERSISTENCY INDEX
Landscape control (exponent of the sediment rating curve, sediment related features)
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PERSISTENT: flows vary weakly
around their mean
ERRATIC: sequence of
very high and very low flows
AN EXPLANATORY FRAMEWORK
Distinct streamflow dynamics imply different
effective discharge
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AN EXPLANATORY FRAMEWORK
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CLIMATE CONTROLS ON EFFECTIVE DISCHARGE
Low rainfall frequency High ET
Low
High CVq
High qf
Elm Fork (TX)
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Photo: FOEN
For details see: Basso et al., Climatic and landscape controls on effective discharge, GRL 2015.
www.catchsolutions.org