Aquaculture in hydropower
reservoirs – consequences for
ecological status and nutrient
fluxes on the catchment scale
Tobias Vrede
Swedish University of Agricultural Sciences,
Department of Aquatic Sciences and Assessment
Focus of this talk
•  Hydropower reservoir ecosystems and
ecological status
•  Some of AQUABEST spatial planning
recommendations:
•  Track sources and fluxes of nutrients in regulated
rivers
•  Monitor for potential environmental impacts
Water level (m a s l) 555 553 regulated 551 549 547 unregulated 545 543 0
8
16
24
32 week 40
48
Fishing
Feed Harvest
Hydropower
reservoir
Input from
upstream
Aquaculture
Losses from
aquaculture
Littoral
food web
Planktonic food web
Suspended
nutrients
Sedimentation &
resuspension
Sediment
Whole
catchment
Benthic food web
Downstream
transport
Retention in
the catchment
Baltic
Sea
Biological integrity
The ability [of an ecosystem] to support and
maintain a balanced, integrated, and adaptive
community of organisms having a species
composition, diversity and functional organization
comparable to those of natural habitats within a
region.
Karr & Dudley 1981
Regulation amplitude in
large (>10 km2) lakes and
hydropower reservoirs in
Northern Sweden
unregulated
< 1 m 1-­3 m
3-­10 m
>10 m
Data from SMHI lake and dam registers
Dramatically decreased Arctic char growth
in hydropower reservoirs
unregulated
regulated
300
200
100
Juvuln
Ånnsjön
Västansjön
Värjaren
Messlingen
Lejaren
Ankarvattnet
0
Abiskojaure
Weight (g)
400
-10
0
10
20
30
40
50
Years after impoundment
Milbrink, Vrede, Tranvik & Rydin (2011)
Can J Fish Aquat Sci 68:2167–2173
60
70
Nutrient enrichment can restore wild char growth
400
Compensatory
enrichment
200
100
Juvuln
Ånnsjön
Västansjön
Värjaren
Messlingen
Lejaren
Ankarvattnet
0
Abiskojaure
Weight (g)
nutrient
300
-10
0
10
20
30
40
50
Years after impoundment
Milbrink, Vrede, Tranvik & Rydin (2011)
Can J Fish Aquat Sci 68:2167–2173
60
70
P retention
HELCOM PLC-5
Total phosphorus
concentration
Total P concentration in a
catchment perspective
Tot-P background
Tot-P max
Highest coast line
mountain
forest
agriculture
river
mouth
Markensten, Fölster, Vrede & Djodjic (2012)
Inst för vatten och miljö, SLU, rapport 2012:20
Total phosphorus
concentration
Total P concentration in a
catchment perspective
Tot-P background
Tot-P max
Tot-P with point source 1
Tot-P with point source 2
Highest coast line
mountain
forest
•  Decision tools are
needed
•  Exactly how large is the
retention?
•  Can we make reliable
estimates of allowable
nutrient load (taking into
account other activities)?
agriculture
river
mouth
•  How will climate
change change the
outcome?
Markensten, Fölster, Vrede & Djodjic (2012)
Inst för vatten och miljö, SLU, rapport 2012:20
Monitoring nutrients
It’s important to recognize variation and extremely low
concentrations!
'#"
!"!#$%&'()*+%
'!"
&"
%"
$"
#"
!"
#!!!"
#!!#"
#!!$"
#!!%"
#!!&"
#!'!"
Advice on monitoring
•  Measure
•
•
•
•
nutrients & oxygen (primary stressors),
sediment nutrients and composition
phytoplankton (quick response biota) and
benthic fauna (possibly most heavily affected biota)
•  Use proper sampling and analytical methods!
•  Start long before establishment of aquaculture
Take home message
•  There is a potential for increased aquaculture
that is ecologically sustainable in hydropower
reservoirs
•  Exploit this potential with great care, considering
both local effects and larger scale nutrient fluxes
Acknowledgements
Martyn Futter, Hampus Markensten, Jens Fölster, Faruk Djodjic
Göran Milbrink, Emil Rydin, Lars Tranvik
Erik Olofsson, Tina Hedlund, Anders Kiessling
Anders Alanärä