Oct 2008
The future Ems System:
restored by the power of
‘nature’
or
‘engineers’ ?
Prof. Dr. Victor N. de Jonge DSc 1 & Dr. Henk Schuttelaars 2
1 IECS, University of Hull, United Kingdom2 TUD, Delft, The Netherlands
Sunrise or Sunset
for the Ems estuary ?
Starting point:
The Ems estuary between the
North Sea and the weir at Herbrum
is one undividable system
Challenge:
How we can restore it
STRUCTURE OF TALK
1. What happened to the Ems estuary and its river?
2. What were the resultant environmental changes to
the Ems river and Ems estuary?
3. Options on ‘how to proceed’
1.What happened to the river ?
Canalisations, deepenings & dredging
result: 10 times more suspended mud
1.What happened to the estuary ?
Varying but large scale channel dredging
result: 2.5 – 3 times more suspended mud
+
Ems estuary River Ems
110200
900
0
200
400
600
800
1000
1200
0 10 20 30 40 50 60 70 80 90 100
1975/ 76
0
200
400
600
800
1000
1200
0 10 20 30 40 50 60 70 80 90 100
2005/ 06
mean suspended matter concentration in the Ems estuary (near water surface)
0
200
400
600
800
1000
1200
0 10 20 30 40 50 60 70 80 90 100
distance from Herbrum (km)
mean SPM
(g.m-3
)
1954
Leer HGOEHEmdenRiver SeaP’burg
Zoom in
fit 28 - 100 km
1975-1976
y = 1181e-0.0403x
R2 = 0.9396
2005-2006
y = 8244.5e-0.0624x
R2 = 0.9722
1992-1993
y = 8528.5e-0.0628x
R2 = 0.8620
1954
y = 531.9e-0.0448x
R2 = 0.5333
0
200
400
600
800
1000
30 40 50 60 70 80 90 100
Km from weir Herbrum
SPM
(gm-3
)
BorkumEemshavenEmden
1954 ‘reference’ situation
1975-1976 provides effect of channel maintenance dredging (CMD)
1992-1993 combines effect of CMD + Ems canalisation and deepening
2005-2006 combines effect of CMD + Ems canalisation and deepening
Ems estuary
fit 28 - 100 km
1975-1976
y = 1181e-0.0403x
R2 = 0.9396
2005-2006
y = 8244.5e-0.0624x
R2 = 0.9722
1992-1993
y = 8528.5e-0.0628x
R2 = 0.8620
1954
y = 531.9e-0.0448x
R2 = 0.5333
0
25
50
75
100
70 75 80 85 90 95 100 105 110
Km from weir Herbrum
SPM
(gm-3
)
BorkumEemshaven
1. 1975-1976:
channel change
2. Steep slope
since 1992-1993
3. Effect
measurable until
Eemshaven
4. 2.5 to
3-fold increase
Why important ?
This is the area where the food is produced for the rest of the system
also the river !
2. The resultant environmental
changes to
the Ems river and Ems estuary
sea
Phosphate, Fe, Al, dissolved organic C concentration
salinity
Ems estuary
Van Beusekom & de Jonge 1998
- extremely high SPM (organic material included)
- extremely high BOD
- extreme fluctuation in phosphorous levels
- extremely low minimum oxygen in summer
- extreme environment to organisms with gills
Minimum oxygen concentration in ETM as function of temperature
y = 0.0056x3 - 0.223x2 + 2.0893x + 4.3071
R2 = 0.9934
0
2
4
6
8
10
12
0 5 10 15 20 25
Water temperature (oC)
Oxygen
(mg l-1)
ALGAL GROWTH
(tonnes organic C a-1)
LOWER
REACHES
MIDDLE
REACHESDOLLARD
TOTAL
ESTUARY
Reference conditions
(no dredging)160000 200000
Measured
(1975 - 1980)
35km estuarine dredging120000
estuarine dredging +
river improvements
(2005 - 2006)
75000
THE ULTIMATE PROBLEMS IN SUMMARY
fit 28 - 100 km
1975-1976
y = 1181e-0.0403x
R2 = 0.9396
2005-2006
y = 8244.5e-0.0624x
R2 = 0.9722
1992-1993
y = 8528.5e-0.0628x
R2 = 0.8620
1954
y = 531.9e-0.0448x
R2 = 0.5333
0
25
50
75
100
70 75 80 85 90 95 100 105 110
Km from weir Herbrum
SPM
(gm-3
)
ALGAL GROWTH
Primary production (%)
LOWER
REACHES
MIDDLE
REACHESDOLLARD TOTAL ESTUARY
Reference conditions
(no dredging)82 12 6 100 (%)
Measured
(1975 -1980)
35km estuarine dredging62
Estuarine dredging +
river improvements
(2005 – 2006)38
THE ULTIMATE PROBLEMS IN SUMMARY
Minimum oxygen concentration in ETM as function of temperature
y = 0.0056x3 - 0.223x2 + 2.0893x + 4.3071
R2 = 0.9934
0
2
4
6
8
10
12
0 5 10 15 20 25
Water temperature (oC)
Oxygen
(mg l-1)
3. How to proceed technically?
Knock
Emden Leer Herbrum
The ‘power of nature’ acting on the Ems has been amplified by the
‘power of the engineers’ changing the morphology of the river.
3510 65 km from Knock
1. Increasing the length of
the freshwater tidal river
2. Creating a ‘sill’ in the
lower tidal river between
Emden and Leer
Natural depth profile and ETM natural depth profile
ETM for natural depth profile but longer tidal river part upstream Herbrum weir
Knock Herbrum
Maximum near bottom concentrations of mud
Knock Emden Leer
Leer Herbrum
Sill option in river
Another convergence/ mud
accumulation area
upstream the sill
This is
upstream
Emden
- CHANGE EXTERNAL BOUNDARY CONDITIONS
1. Shipbuilding is partly done modulary.
Hull construction and heavy engines could be completed ‘upstream’
Completion (eg cabin mounting) above the engine-room could be
done near deep water
2. The present location of the weir is, given the present boundary
conditions, questionable. Upstream replacement is an option in
combination with restoring river meanders (lengthening the fresh
water tidal river.
3. The incoming tidal wave from the North Sea is very powerful. Seen
the upstream consequences of it, ‘shallows’ seaward from the tidal
inlet could reduce the tidal energy there instead of upstream
4. …. There are some more options
3. How to proceed technically?
Thank you
- TECHNICALLY: CHANGE BOUNDARY CONDITIONS
1. Shipbuilding is partly done modulary. Hull construction and heavy
engines could be completed in ‘upstream’ while completion (eg
cabins) above the engine-room could be done near deep water
2. The present location of the weir is, given the present boundary
conditions, questionable. Upstream replacement is an option in
combination with restoring river meanders (lengthening the fresh
water tidal river.
3. The incoming tidal wave from the North Sea is very powerful. Seen
the upstream consequences of it, ‘shallows’ seaward from the tidal
inlet could reduce the tidal energy there instead of upstream
4. Another option is a much longer new canal from circa Dörpen to
Pogum connecting the Ems estuary to the Dortmund-Ems Kanal
brings the water back where it was and provides big chances to
industry, area, river, ecology landscape and economy. Active river
undeepening may be necessary.
3. How to proceed ?
28 - 95 km
0.0
200.0
400.0
600.0
800.0
1000.0
1200.0
0.0 20.0 40.0 60.0 80.0 100.0
1992/ 93
2005/ 06
BorkumEemshavenEmdenLeerPapenburg
Between 1980 and 1992 the system dynamics
significantly and structurally changed
Since then the system seems to be in another
‘steady state’
Fluid mud pool act
as a mud sink
Maximum dredging distance was
51.4 km in 1972 &
51.3 km in 1978
Curves calculated based on a statistical model and thus not predictive
Findings published internationally by de Jonge in 1983 and 2000
0
50
100
150
200
0 20 40 60 80 100
Distance (km)
SPM
(gm-3)
[35 km dredging]
[0 km dredging]
[50 km dredging]
Curves valid for 1954 (?), 1970 – 1979
(unchanged turbidity maximum, minimum mud disposal)
Natural situation
‘no dredging’
BorkumEemshEmdenHerbrum
(Fixed turbidity maximum)
Figure copied from Restoration Plan Ems and Dollard (Waddenvereniging 1999)
Publication in Dutch and German
Ongoing for already
30 years
Threshold for fish
No anticipation to these negative
environmental developments, which forms
a general problem in both countries.
- IN TERMS OF PROCEDURES:
1. Economic, ecological as well as social monitoring activities in the
estuary, on the river, along the Ems system and in the drainage basin
upstream should be carried out in co-operation between both countries
because there is a joint interest
2. An international restoration plan for the entire drainage basin should
be prepared and agreed upong at the highest possible level between
both countries (see advice by Wadden Sea Council)
3. A geographical restructuring of industrial, rural and leisure activities
required, in combination with other Belgian, Dutch, German regions
4. Giving ‘space to the power of nature’ should be practiced from both
an environmental and an economic perspective
4. How to proceed ?
Ecosystem Functions & Functioning
Ecosystem Services & Goods
Decision-making processes
Sustainable Management
Ecosystem Value
Ecosystem functions:
1. Regulation
2. Habitat
3. Production
4. Information
Ecosystem Services &
Goods
Ecological values
based on ecological sustainability
Economic values
based on efficiency and cost-effectiveness
Ecosystem Structure & Processes
Social-cultural values
based on equity and cultural perceptions
Total Value
Decision making process
After de Groot et al., 2002
Talking about the system values .......
this combination
represents the total
system value
ALGAL GROWTH
(tonnes organic C a-1)
LOWER
REACHES
MIDDLE
REACHESDOLLARD
TOTAL
ESTUARY
Reference conditions
(no dredging)160555 24316 11380 196251
Measured
(1975 - 1980)
35km estuarine dredging95895 15384 9721 121000
estuarine dredging +
river improvements
(2005 - 2006)
55757 9046 8892 73695
THE ULTIMATE PROBLEMS IN SUMMARY
ALGAL GROWTH
Primary production (%)
LOWER
REACHES
MIDDLE
REACHESDOLLARD TOTAL ESTUARY
Reference conditions
(no dredging)82 (100%) 12 (100%) 6 (100%) 100 (100%)
Measured
(1975 -1980)
35km estuarine dredging49 (60%) 8 (67%) 5 (83%) 62 (62%)
Estuarine dredging +
river improvements
(2005 – 2006)28 (34%) 5 (42%) 5 (83%) 38 (38%)
In terms of ‘compensation measures’ the value of this algal
growth to the functioning of the Ems system AND the UNESCO
World Heritage Wadden Sea needs to be calculated and
applied to come to future solutions in monetary units
- STARTING POINTS:
1. The Ems estuary is one undividable system
2. Do not exceed the limits of ‘evidence’
(Ian Townend, Wallingford, UK)
3. Get everybody involved
(also ‘locals’)
4. Think ‘out of the box’, ‘look over the fence’, being flexible ….
5. Create long term perspective …..
(not only economically ! Also ecologically, socially & culturally !)
3. How to proceed ?
Changes for the river in summary:
increased tidal range, lower low tides,
amplified flood currents, amplification of
gravitational circulation, higher SPM
(worsened light conditions) and related lower
algal growth and low oxygen values