How Clean is the Thames?
Martin J Attrill
Marine Biology & Ecology Research Centre
University of Plymouth
mattrill@plymouth.ac.uk
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
End of C19th – world’s
largest city (4.7 million
people)
Major potential impact on the estuarine system
Historical Context: main uses of the
estuary and their impact
1. Navigation
• Construction of weirs
• By 1809 - 26 on Thames
• Impacted migratory fish
Salmon
caught at
Boulter’s
lock
Romney weir - Windsor
Historical Context: main uses of the
estuary and their impact
2. Bankside development
• Loss of surrounding
marshes
• Narrowed estuary – deeper
• Intensive Flood defences
• Removed natural foreshore
River Tyburn
Thorney
Island
Historical Context: main uses of the
estuary and their impact
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
UCLA
1856 map of regions served by
different water companies
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 (KewGravesend)
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
Flounder
Whiting
• Steady increase in
species recorded
• Some unusual species
encountered
Cumulative species number
Historical Context: Trends in fish
recovery: 1960s-1980
120
100
80
60
40
20
0
64 66 68 70 72 74 76 78 80 82 84 86 88
Year
Where are we now? Trends in water
quality since rehabilitation
Analysis of long-term data from Environment Agency
Naturally rivers and estuaries
Less muddycan
than
carry lots of mud particles
(e.g.
pre-1992
Amazon). “Dirty” does not always
mean polluted!
180
160
140
120
100
80
60
Year
05
20
03
20
01
20
99
19
97
19
95
19
93
19
91
19
89
19
87
19
85
19
83
19
81
19
79
19
77
40
20
0
19
Suspended Solids (mg/l)
1. Suspended solids (Kinks – “Dirty Old River”)
Where are we now? Trends in water
quality since rehabilitation
2. Heavy Metals (mainly from industry, since 1980)
Can be toxic to estuary life, e.g. copper, nickel, mercury, zinc
Power, Attrill, Thomas (1999). Water Res. 33: 1672-1680
Where are we now? Trends in water
quality since rehabilitation
3. Pesticides (mainly from agriculture runoff, since 1988)
Exponential decrease in
both metal and pesticide
contamination since
1980s
Power, Attrill, Thomas (1999). Environ. Pollut. 104: 31-39
Where are we now? Trends in water
quality since rehabilitation
4. Fertilisers (mainly from agriculture, since 1980)
Can cause eutrophication, algal blooms, etc.
10
Nitrogen
8
7
6
Significant decrease over last 30 years
5
Year
05
20
03
20
01
20
99
19
97
19
95
19
93
19
91
19
89
19
87
19
85
19
83
19
81
19
79
19
77
4
19
Nitrogen (mg/l)
9
Where are we now? Trends in water
quality since rehabilitation
4. Fertilisers (mainly from agriculture, since 1980)
Can cause eutrophication, algal blooms, etc.
Phosphate
2
1.5
1
0.5
Significant decrease over last 18 years
Year
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
0
1988
Orthophosphate (mg/l)
2.5
Where are we now? Trends in water
quality since rehabilitation
5. Dissolved Oxygen (essential for life, affected by
bacteria breaking down organic material)
65
60
55
50
45
40
Lowest average oxygen since mid 1970s
35
Year
05
20
03
20
01
20
99
19
97
19
95
19
93
19
91
19
89
19
87
19
85
19
83
19
81
19
79
19
77
30
19
Dissolved Oxygen (mg/l)
70
Where are we now? Trends in water
quality since rehabilitation
Year
05
20
03
20
01
20
99
19
97
19
95
19
93
19
91
19
89
19
87
19
85
19
83
19
81
19
79
Worrying decline in minimum oxygen
19
77
50
45
40
35
30
25
20
15
10
5
0
19
Minimum Dissolved Oxygen (mg/l)
5. Dissolved Oxygen
Where are we now? Trends in water
quality since rehabilitation
6. Fish community
More recent returns
Sea lamprey
Number of species per
sample - rolling mean
22
20
18
16
14
.
12
10
1974
1992
Year
Twaite Shad
Number of species in power
station fish samples
Continued improvements to fish biodiversity
Where are we now? Trends in water
quality since rehabilitation
• 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?
Current problems in the Thames Estuary
1. Water temperatures – global warming
Temperature (° C)
20
18
Average annual water temperature
16
14
12
10
Year
2.7C increase in 30 years… linked to:
05
20
03
20
01
20
99
19
97
19
95
19
93
19
91
19
89
19
87
19
85
19
83
19
81
19
79
19
19
77
8
Current problems in the Thames Estuary
2. Dissolved Oxygen Sags in Summer
Sewer system cannot cope with summer flash floods
Aug 2004
Combined Sewer Overflow
Current problems in the Thames Estuary
2. Dissolved Oxygen Sags in Summer
From Thames Tideway Strategic Study
• Warm water
• Fast bacterial breakdown
• Oxygen removed quickly
• Elevated E. coli counts (health risk)
Current problems in the Thames Estuary
2. Dissolved Oxygen Sags in Summer
From Thames Tideway Strategic Study
•Thames Bubbler – treats symptoms
• Build new interceptor system under
estuary?
Linked to…
Current problems in the Thames Estuary
3. Drought conditions
1976 – no water coming
over Teddington Weir
Kew, 1990
• Increasing demand in drinking water for London.
• Reduced flow impacts ecology of estuary and rate of
pollution dispersal (e.g. CSO incidents)
Current problems in the Thames Estuary
3. Drought conditions
Abstraction (million m3)
Rate of abstraction
250
200
150
100
50
0
1900
1920
1940
1960
1980
2000
Year
flow
Exacerbates CSO and
STW input problem
1400
River Flow (million m3)
Rate of Thames flow
rolling mean
1200
1000
800
600
400
200
0
1900
1920
1940
1960
Year
1980
2000
Current/Future problems in the Thames Estuary
4. Sea level rise
Predicted sea level rise
Global Sea Level Rise (mm)
700
Canvey Island 1953
600
UK Met. Office 1998
500
Greenland ice
400
300
Glaciers etc
200
100
Thermal exp
2100
2080
2060
2040
2020
2000
1980
1960
1940
1900
1860
0
FCDE
Annual Sea Level
Sheerness
London 2100?
Current/Future problems in the Thames Estuary
4. Sea level rise - Need to plan now…but what to do?
Managed realignment?
Canvey
Island
Example of a 'hard' flood
defence option:
Build bigger defences?
Example of managed
realignment:
Current/Future problems in the Thames Estuary
4. Sea level rise - Need to plan now…but what to do?
Outer
Estuary
Barrier?
End of estuary as we know it
Thank you!
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