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How Clean is the Thames?
Martin J Attrill
Marine Biology & Ecology Research CentreUniversity of Plymouth
Plan of Lecture: How clean is the Thames
• Historical context– Background– Uses– History of pollution and
recovery
• Where are we now?– Trends from 1970s to
present day
• What about the future?– Current and impending
problems
Historical Context: Background • 110 km long Teddington Weir - Southend, via London
Change in the size of London
Major potential impact on the estuarine system
End of C19th – world’s largest city (4.7 million people)
Historical Context: main uses of the estuary and their impact
1. Navigation• Construction of weirs• By 1809 - 26 on
Thames• Impacted migratory
fish
Romney weir - WindsorSalmon caught at Boulter’s lock
2. Bankside development• Loss of surrounding
marshes• Narrowed estuary –
deeper• Intensive Flood defences
• Removed natural foreshore
Historical Context: main uses of the estuary and their impact
River Tyburn
ThorneyIsland
3. Drinking water supply
• Thames has always supplied London’s water
• Originally taken from upper estuary
• Water companies set up from 1600s to deliver water
1856 map of regions served by different water companies
Historical Context: main uses of the estuary and their impact
UCLA
Historical Context: main uses of the estuary and their impact
4. Waste disposal• C19th – waste in streets &
tributaries flushed into estuary
• Cholera – 1849
Historical Context: main uses of the estuary and their impact
4. Waste disposal• Major impact on
water quality in estuary
• 1858 – the year of the “Great Stink”
Come, my dear! Come to the old Thames and have a nice bath! - Punch, June, 1859
Historical Context: Plans to rehabilitate the estuary: 19th
Century
• 161 km gravity interceptor sewer constructed (1860s)
• Sewage discharged at Barking
• London cleaner…but not the mid-estuary
• Extensive “mud” banks• Fishery destroyed
(1320 men employed)
Historical Context: Plans to rehabilitate the estuary: 19th Century
• 1878 “Princess Alice” disaster
• Settlement ponds introduced – sludge dumped in outer estuary (continued until 1998)
Historical Context: Plans to rehabilitate the estuary: 19th Century
• By end of 19th Century water quality improved
• Fish returned (e.g. sprat)
Historical Context: It all goes wrong again: 20th Century
• Post WWI – massive increase in population
• WWII – huge damage to London infrastructure
• No funds for repair and improvement to old and damaged sewer system
Historical Context: It all goes wrong again: 20th Century
• 1950s – worse the Thames had ever been
• 52 km dissolved O2 <5%
• 20 km no measurable oxygen
• No fish populations for 69 km of estuary (Kew-Gravesend)
Tubifex
Historical Context: The second rehabilitation: 1960s-1970s
• 1960s – economic recovery
• Investment in sewage works – tertiary treatment at outfalls
• By 1976 all sewage fully treated - dramatic increase in water quality
Crossness STW outfall
Historical Context: Trends in fish recovery: 1960s-1980
• Fish used to monitor recovery of system
• Combination of methods, including power station intakes
• First returning fish recorded in early 1960s
Eel WhitingFlounder
Historical Context: Trends in fish recovery: 1960s-1980
• Steady increase in species recorded
0
20
40
60
80
100
120
64 66 68 70 72 74 76 78 80 82 84 86 88Year
Cum
ulat
ive
spec
ies
num
ber
• Some unusual species encountered
Where are we now? Trends in water quality since rehabilitation
1. Suspended solids (Kinks – “Dirty Old River”)
Naturally rivers and estuaries can carry lots of mud particles (e.g. Amazon). “Dirty” does not always mean polluted!
0
20
40
60
80
100
120
140
160
180
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
Year
Su
sp
en
de
d S
olid
s (
mg
/l) Less muddy than pre-1992
Analysis of long-term data from Environment Agency
2. Heavy Metals (mainly from industry, since 1980)
Power, Attrill, Thomas (1999). Water Res. 33: 1672-1680
Where are we now? Trends in water quality since rehabilitation
Can be toxic to estuary life, e.g. copper, nickel, mercury, zinc
Power, Attrill, Thomas (1999). Environ. Pollut. 104: 31-39
3. Pesticides (mainly from agriculture runoff, since 1988)
Where are we now? Trends in water quality since rehabilitation
Exponential decrease in both metal and pesticide contamination since 1980s
Where are we now? Trends in water quality since rehabilitation
4. Fertilisers (mainly from agriculture, since 1980)
4
5
6
7
8
9
10
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
Year
Nit
rog
en
(m
g/l)
Can cause eutrophication, algal blooms, etc.
Nitrogen
Significant decrease over last 30 years
Where are we now? Trends in water quality since rehabilitation
4. Fertilisers (mainly from agriculture, since 1980)
Can cause eutrophication, algal blooms, etc.
0
0.5
1
1.5
2
2.5
19
88
19
89
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
Year
Ort
ho
ph
os
ph
ate
(m
g/l) Phosphate
Significant decrease over last 18 years
Where are we now? Trends in water quality since rehabilitation
5. Dissolved Oxygen (essential for life, affected by bacteria breaking down organic material)
30
35
40
45
50
55
60
65
70
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
Year
Dis
so
lve
d O
xy
ge
n (
mg
/l)
Lowest average oxygen since mid 1970s
Where are we now? Trends in water quality since rehabilitation
5. Dissolved Oxygen
05
101520253035404550
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
Year
Min
imu
m D
iss
olv
ed
Ox
yg
en
(m
g/l)
Worrying decline in minimum oxygen
Where are we now? Trends in water quality since rehabilitation
6. Fish community
10
12
14
16
18
20
22
Year
Nu
mb
er o
f sp
ecie
s p
er
sam
ple
- r
oll
ing
mea
n
.
1974 1992
Number of species in power station fish samples
More recent returns
Sea lamprey
Twaite Shad
Continued improvements to fish biodiversity
• Summary– Metals, pesticides and nutrients all show significant
declines. Thames now likely to be cleanest in living memory in terms of these pollutants.
– Amount of suspended solids in the water has stabilised at a lower level than previous years.
– Most expected fish species are present– Recent years, however, have seen a decrease in
levels of oxygen in the estuary.
– WHY?
Where are we now? Trends in water quality since rehabilitation
Current problems in the Thames Estuary
1. Water temperatures – global warming
8
10
12
14
16
18
20
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
Year
Te
mp
era
ture
(°
C) Average annual water temperature
2.7C increase in 30 years… linked to:
2. Dissolved Oxygen Sags in Summer
Current problems in the Thames Estuary
Sewer system cannot cope with summer flash floods
Aug 2004
CSO
Combined Sewer Overflow
2. Dissolved Oxygen Sags in Summer
Current problems in the Thames Estuary
• Warm water• Fast bacterial breakdown• Oxygen removed quickly• Elevated E. coli counts (health risk)
From Thames Tideway Strategic Study
•Thames Bubbler – treats symptoms• Build new interceptor system under estuary?
From Thames Tideway Strategic Study
2. Dissolved Oxygen Sags in Summer
Current problems in the Thames Estuary
Linked to…
3. Drought conditions
Current problems in the Thames Estuary
Kew, 1990
1976 – no water coming over Teddington Weir
• Increasing demand in drinking water for London.• Reduced flow impacts ecology of estuary and rate of pollution dispersal (e.g. CSO incidents)
3. Drought conditions
Current problems in the Thames Estuary
0
50
100
150
200
250
1900 1920 1940 1960 1980 2000
Year
Ab
stra
ctio
n (
mill
ion
m3)
Rate of abstraction
Rate of Thames flow
0
200
400
600
800
1000
1200
1400
1900 1920 1940 1960 1980 2000
Year
Riv
er F
low
(m
illio
n m
3)
flow rolling mean
Exacerbates CSO and STW input problem
4. Sea level rise
Current/Future problems in the Thames Estuary
Canvey Island 1953
London 2100?Annual Sea LevelSheerness
FCDE
Global Sea Level Rise (mm)
Thermal exp
Glaciers etc
Greenland ice
0
100
200
300
400
500
600
700
186
0
190
0
194
0
196
0
198
0
200
0
202
0
204
0
206
0
208
0
210
0
UK Met. Office 1998UK Met. Office 1998
FCDE
Global Sea Level Rise (mm)
Thermal exp
Glaciers etc
Greenland ice
0
100
200
300
400
500
600
700
186
0
190
0
194
0
196
0
198
0
200
0
202
0
204
0
206
0
208
0
210
0
UK Met. Office 1998UK Met. Office 1998
FCDE
Global Sea Level Rise (mm)
Thermal exp
Glaciers etc
Greenland ice
0
100
200
300
400
500
600
700
186
0
190
0
194
0
196
0
198
0
200
0
202
0
204
0
206
0
208
0
210
0
Thermal exp
Glaciers etc
Greenland ice
0
100
200
300
400
500
600
700
186
0
190
0
194
0
196
0
198
0
200
0
202
0
204
0
206
0
208
0
210
0
UK Met. Office 1998UK Met. Office 1998
Predicted sea level rise
4. Sea level rise -
Current/Future problems in the Thames Estuary
Need to plan now…but what to do?
Canvey Island
Example of managed realignment:
Example of a 'hard' flood defence option:
Managed realignment?
Build bigger defences?
4. Sea level rise -
Current/Future problems in the Thames Estuary
Need to plan now…but what to do?
Outer EstuaryBarrier?
End of estuary as we know it
Thank you!
http://www.thamesweb.com/
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