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A WATER FRAMEWORK DIRECTIVE (WFD) COMPLIANT DETERMINATION OF ECOLOGICALLY ACCEPTABLE
FLOWS FOR ALPINE RIVERS IN AUSTRIA
A. ZITEK1 , P. JÄGER2, B. ZEIRINGER3
1 EcoScience, Environmental Studies, Goldschlagstraße 209/6 1140 Vienna,
Email: andreas.zitek@ecoscience.at2 Ingenieurbüro für Ökologie und Umweltbiologie
Brunn 147, 5201 Seekirchen am Wallersee, AustriaEmail: paul.jaeger@sbg.at
3 Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Vienna, Austria
Email: bernhard.zeiringer@boku.ac.at
Content
• Study area• Aim of the study• Residual flow assessments
• Methods• Results
• Conclusion
Mur
Salzach
Study sites in Salzburg -Austria
Water abstraction sites at 20 power plants at mainly wadeablerivers at 63 river stretches (40 water abstraction sites, 23 full water sites),
Residual flow < MALFResidual flow > MALF
Hydropeaking < 1:5
Hydropeaking > 1:5
Characteristics of the assessedriver stretches
Slop
e%
Aim of the study
• Evaluation of the existing hydromorphologicalsignificance criteria used to pre-classify the currentecological status of rivers with regard to the EU Water Framework Directive formacrozoobenthos and fish with regard to:•• EcologicallyEcologically acceptableacceptable minimumminimum flowflow at at waterwater
abstractionabstraction sitessites
•• Central Central questionquestion: : cancan thethe good good ecologicalecologicalstatusstatus ((WFDWFD--terminologyterminology) ) cancan bebeachieved/maintainedachieved/maintained whenwhen usingusing thisthissignificancesignificance criteriacriteria ??
Methods
Structure of the residual flow assessmentSignificance criteriaSignificance criteria
• Ecologically acceptable flow > Natural absolute daily minimum flow (nat. ADMF)
• MALF residual > MALF (as total annual discharge load)
Testing for ecological relevance – is more water needed?
• Fish ecological judgement using Fish Index Austria
• Macrozoobenthos,
• Hydraulic habitat analysis
• Habitat modelling
Testing and validating additional parameters to define the ecologically acceptable flow
• Maximum depth in the cross section of the minimum (“pessimum”) riffle
• v_mean in the cross section of the pessimumriffle
• Mean thalweg depth
• Residual pool depth as a measure for morphology
Additional parameters for determiningecologically acceptable minimum flow
≥ 0,30,600,40≥ 0,30,30Epipotamal
≥ 0,30,500,30 (0,402)≥ 0,30,20 (0,302)Hyporhithral
≥ 0,30,300,30≥ 0,30,20Metarhithral
≥ 0,30,250,25≥ 0,30,20Epirhithral (≤ 3% Gefälle)
≥ 0,30,200,20≥ 0,30,15Epirhithral (3-10% Gefälle)
≥ 0,30,150,15≥ 0,30,10Epirhithral (> 10% Gefälle)
Leitströmung imWanderkorridorvmin [m/s]
Zur Laichzeit:ØMindesttiefe (1)TLZ [m]
Zum Erhalt des Lebensraumes: Ø MindesttiefeTLR [m]
Mindestfließ-geschwindigkeitvmin [m/s]
Mindestwasser-Tiefe Tmin [m]
Für den TalwegFür den Bereich der Schnelle
Fließgewässerzone
≥ 0,30,600,40≥ 0,30,30Epipotamal
≥ 0,30,500,30 (0,402)≥ 0,30,20 (0,302)Hyporhithral
≥ 0,30,300,30≥ 0,30,20Metarhithral
≥ 0,30,250,25≥ 0,30,20Epirhithral (≤ 3% Gefälle)
≥ 0,30,200,20≥ 0,30,15Epirhithral (3-10% Gefälle)
≥ 0,30,150,15≥ 0,30,10Epirhithral (> 10% Gefälle)
Leitströmung imWanderkorridorvmin [m/s]
Zur Laichzeit:ØMindesttiefe (1)TLZ [m]
Zum Erhalt des Lebensraumes: Ø MindesttiefeTLR [m]
Mindestfließ-geschwindigkeitvmin [m/s]
Mindestwasser-Tiefe Tmin [m]
Für den TalwegFür den Bereich der Schnelle
Fließgewässerzone
Pessimum riffle Thalweg
Mean depth(m)
Mean depthspawningtime (m)
Minimum flow vel.
(m/s)
Minimum depth
(m)
Minimum profile flowvel. (m/s)
River region
slope
slope
slope
Measurement & sampling design
Macrozoobenthos (Saproby and species specific analysis)
Lower end of residual flow stretch
Upstream water abstraction
Upper end of residual flow stretch
Downstream water abstraction
Fish ecological status (Fish Index Austria)
Hydraulic & habitat mapping
Measurements at 200 m sections
Discharge
Wetted width
Maximum depth pessimum riffle
Mean Profile flow velocity at pessimum riffle
Pool depths (n=5)
Riffle depths (n=5)
=> Mean thalweg depth
At three discharges (< MALF, MALF, > MALF)
Additional measurementsWidth at MAF Bankfull widthLocal slope
Standard residual flow assessmentStandard residual flow assessment(Guideline for defining ecologically acceptable (Guideline for defining ecologically acceptable
flow, Salzburg, flow, Salzburg, JJäägerger et al. 2008)et al. 2008)
KW Maria Sorg Restwasserstrecke
0,00
0,05
0,10
0,15
0,20
0,25
0,30
0,35
0,40
0,45
0,50
0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 0,90 1,00 1,10 1,20
Q [m³/s]
Tmin
[m]
Hydraulic signatures for ecological modelling at different scales, Yann Le Coarer, Aquatic Ecology (2007) 41:451–459
Hydraulic mapping mapping Hydraulic mapping mapping (after (after ParasiewiczParasiewicz, 2007), 2007)
Target: systematic and stratified assessment of depth-flow velocity patterns at different discharges- Hydro-morphological units HMU) for orientation and stratification (7-15 measurements per HMU).
Characterisation of Characterisation of instreaminstream sediment sediment incl. qualitative assessment of incl. qualitative assessment of embeddednessembeddedness and proportion of fines, and proportion of fines, instreaminstream structures (different types structures (different types -- no, no, existing, abundant), shoreline structure existing, abundant), shoreline structure and land useand land use
Pressure/Site Site 1 Site 2 Site 3 Site 4Water abstractionHydro-peakingMorphological changeTemperature changeImpoundmentConnectivity lossEmbeddednessCatchment Land useSediment flushingWater quality
Identification of pressure combinations and main pressures
0
2
4
6
8
10
12
14
16
18
20
01.01
.2003
01.02.20
0301
.03.200
301
.04.20
0301.0
5.2003
01.06
.2003
01.07
.2003
01.08.20
0301
.09.200
301
.10.20
0301.1
1.2003
01.12.2
003
Date
Dis
char
ge [m
³/s]
Qresidual
Qdefined
Daily mean discharge at abstraction site
Is this enough to fulfil ecological requirements?
Constructing the hydrograph at water abstraction sites
Turbine uptake capacity
Natural minimum flow
Main resultshydraulicmapping
Results hydraulic mapping: Changes of flow velocity distributions with
decreasing discharge
Reducation of substrate movingdischarges (MAF+20%)
KW Spannberg 2003 Wasserfassung
Vergleich natürliche Jahresganglinie mit Jahresganglinie in Ausleitung
0
2
4
6
8
10
12
14
16
18
20
01.01
.2003
31.01
.2003
02.03
.2003
01.04
.2003
01.05
.2003
31.05
.2003
30.06
.2003
30.07
.2003
29.08
.2003
28.09
.2003
28.10
.2003
27.11
.2003
27.12
.2003
Datum
Dur
chflu
ss [m
³*s-1
]
Tagesmittel anWasserfassung
QKons
Qrest1
MQ+20%
Zeit MQ+20%
Dynamic discharge in residual flow stretches
KW Winkler 2003 Wasserfassung
Vergleich natürliche Jahresganglinie mit Jahresganglinie in Ausleitung
0
2
4
6
8
10
12
14
01.01
.2003
31.01
.2003
02.03
.2003
01.04
.2003
01.05
.2003
31.05
.2003
30.06
.2003
30.07
.2003
29.08
.2003
28.09
.2003
28.10
.2003
27.11
.2003
27.12
.2003
Datum
Dur
chflu
ss [m
³*s-1
]
Tagesmittel anWasserfassung
QKons
Qrest
MQ+20%
Zeit über MQ+20%
KW Winkler 2004 Wasserfassung
Vergleich natürliche Jahresganglinie mit Jahresganglinie in Ausleitung
0
2
4
6
8
10
12
14
01.01
.2004
31.01
.2004
01.03
.2004
31.03
.2004
30.04
.2004
30.05
.2004
29.06
.2004
29.07
.2004
28.08
.2004
27.09
.2004
27.10
.2004
26.11
.2004
26.12
.2004
Datum
Dur
chflu
ss [m
³*s-1
]
Tagesmittel anWasserfassung
QKons
Qrest
MQ+20%
Zeit über MQ+20%
After After flushingflushing
FlushingFlushing of of sedimentssediments fromfromimpoundmentsimpoundments
DuringDuring flushingflushing
DuringDuring flushingflushingBeforeBefore flusingflusing
Reduction of substrate movingdischarges (MAF+20%) and percentage
of area with medium/high fine sedimentsFi
nes
in s
edim
entm
ediu
m/h
igh
(% o
f tot
al a
rea
map
ped)
Reduction of days with sediment moving discharges
Summary results hydraulicmapping
• At ADMF the highest flow velocity classes were lost in most situations – maintained above MALF.
• Below ADMF flow velocities between 0,0 – 0,4 became dominant– loss of river type specific flow variability and habitats.– increased sedimentation of fines and
• Below ADMF a significant loss of wetted width in relation to the wetted width at MALF leading to significantly reduced ecologically available wetted habitats.
• Below ADMF limits for connectivity for fish like maximum depth at the pessimum profile and minimum flow velocity in thalweg are undercut – sometimes these parameters require more water to be fulfilled!
Main resultsbiology
Relationship between slope and fish biomass
(Spearman-Rho, r=-0,469**, p=0,000). (Spearman-Rho, r=-0,364**, p=0,005)
HydraulicHydraulic stress as stress as factorfactorhighlyhighly negativelynegatively correlatedcorrelatedwithwith fishfish biomassbiomass
Changes in length-frequencydistributions of brown trout
All age classes!
2
3
Mean length and mean weight of brown trout at natural and
residual flow sitesNatural
dischargeResidual
discharge
I
Residual discharge
II
Natural discharge
Natural discharge
Residual discharge
I
Residual discharge
II
Natural discharge
Ecol
. Sta
tus
high
<-F
ish
Inde
x A
ustr
iaju
dgem
ent-
> ec
ol. S
tatu
s ba
d
Fish ecological judgement of river sitesreleated to type of pressure
goodgood
moderatemoderate
Biotic characteristics in significantlyabstracted sites with good ecologcial status
VarianceVariance of of fishfish lengthlength
Good (n=7) Moderate or worse (n=13)
JudgementJudgement of of lenghtlenght--frequencyfrequency distributiondistribution
Good (n=7) Moderate or worse (n=13)
BiomassBiomass
Good (n=7) Moderate or worse (n=13)
Abiotic parameters explaining the good ecological status at significantly abstracted sites
Good (n=7) Moderate or worse (n=13)
MeanMean waterwater depthdepth MeanMean subtsratesubtsrate sizesize
Good (n=7) Moderate or worse (n=13)
Good (n=7) Moderate or worse (n=13)
Relative Relative roughnessroughness
35 % of significantly abstractedsites with good ecological status
• Situated in smaller and steeper rivers, with two of them being situated at the upper end of the fish bearing zone.
• Situated within the trout region with brown trout being the only dominant species.
• Larger mean choriotope size lead to higher values of relative roughness -> habitat heterogeneity -> different size classes of trout -> higher variance of fish lengths -> better judgement of the age distribution.
• The biomass was always considered as satisfyingand biomass KO criterion was never actuated.
Results Macrozoobenthos –reduction of rheophilous species
Num
bero
f rhe
ophi
lous
taxa
Abstraction sites (n=13) Reference (n=10)N
umbe
rof r
heoh
ilous
and
rheb
iont
taxa
Abstraction sites (n=13) Reference (n=10)
Saproby Index failed to assess the impact of waterabstraction on ecological status!
Conclusions• ADMF represents a valid base for determining the ecologically
acceptable base flow -> additional parameters help to maintain important functions like connectivity.
• Experiences: in steep alpine rivers in some cases its hard to reachthe cut value for minimum depth (15-20 cm), in lowland rivers thetrend goes to discharges bigger ADMF to maintain flow velocitiesand depth, some types of rivers show a trend to decreasingminimum flows (climate change) which also needs to beconsidered adequately – next step is regionalisation!
• ADMF = a natural catastrophic event -> a dynamic component to this minimum base flow to maintain the river type specific flow variability is recommended, contributing to the maintenance of natural geomorphologic (e.g. sediment quality) and ecological processes linked to natural flow patterns.
• ADMF and hydromorphological cut values implemented in National Water Act for WFD!
Thank you for your attention!Thank you for your attention!
andreas.zitek@boku.ac.at
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