Presentation is loading. Please wait.

Presentation is loading. Please wait.

How Clean is the Thames? Martin J Attrill Marine Biology & Ecology Research Centre University of Plymouth

Similar presentations


Presentation on theme: "How Clean is the Thames? Martin J Attrill Marine Biology & Ecology Research Centre University of Plymouth"— Presentation transcript:

1 How Clean is the Thames? Martin J Attrill Marine Biology & Ecology Research Centre University of Plymouth

2

3 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

4 Historical Context: Background 110 km long Teddington Weir - Southend, via London

5 Change in the size of London Major potential impact on the estuarine system End of C19 th – world’s largest city (4.7 million people)

6 Historical Context: main uses of the estuary and their impact 1. Navigation Construction of weirs By on Thames Impacted migratory fish Romney weir - Windsor Salmon caught at Boulter’s lock

7 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 Thorney Island

8 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

9 Historical Context: main uses of the estuary and their impact 4. Waste disposal C19 th – waste in streets & tributaries flushed into estuary Cholera – 1849

10

11 Historical Context: m ain 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

12 Historical Context: Plans to rehabilitate the estuary: 19 th 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)

13 Historical Context: Plans to rehabilitate the estuary: 19 th Century 1878 “Princess Alice” disaster Settlement ponds introduced – sludge dumped in outer estuary (continued until 1998)

14 Historical Context: Plans to rehabilitate the estuary: 19 th Century By end of 19 th Century water quality improved Fish returned (e.g. sprat)

15 Historical Context: It all goes wrong again: 20 th 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

16 Historical Context: It all goes wrong again: 20th Century 1950s – worse the Thames had ever been 52 km dissolved O 2 <5% 20 km no measurable oxygen No fish populations for 69 km of estuary (Kew- Gravesend) Tubifex

17 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

18 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 Whiting Flounder

19 Historical Context: Trends in fish recovery: 1960s-1980 Steady increase in species recorded Some unusual species encountered

20 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! Less muddy than pre-1992 Analysis of long-term data from Environment Agency

21 2. Heavy Metals (mainly from industry, since 1980) Power, Attrill, Thomas (1999). Water Res. 33: Where are we now? Trends in water quality since rehabilitation Can be toxic to estuary life, e.g. copper, nickel, mercury, zinc

22 Power, Attrill, Thomas (1999). Environ. Pollut. 104: 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

23 Where are we now? Trends in water quality since rehabilitation 4. Fertilisers (mainly from agriculture, since 1980) Can cause eutrophication, algal blooms, etc. Nitrogen Significant decrease over last 30 years

24 Where are we now? Trends in water quality since rehabilitation 4. Fertilisers (mainly from agriculture, since 1980) Can cause eutrophication, algal blooms, etc. Phosphate Significant decrease over last 18 years

25 Where are we now? Trends in water quality since rehabilitation 5. Dissolved Oxygen (essential for life, affected by bacteria breaking down organic material) Lowest average oxygen since mid 1970s

26 Where are we now? Trends in water quality since rehabilitation 5. Dissolved Oxygen Worrying decline in minimum oxygen

27 Where are we now? Trends in water quality since rehabilitation 6. Fish community Number of species in power station fish samples More recent returns Sea lamprey Twaite Shad Continued improvements to fish biodiversity

28 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

29 Current problems in the Thames Estuary 1. Water temperatures – global warming Average annual water temperature 2.7  C increase in 30 years… linked to:

30 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

31 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

32 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…

33 3. Drought conditions Current problems in the Thames Estuary Kew, – 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)

34 3. Drought conditions Current problems in the Thames Estuary Rate of abstraction Rate of Thames flow Exacerbates CSO and STW input problem

35 4. Sea level rise Current/Future problems in the Thames Estuary Canvey Island 1953 London 2100? Annual Sea Level Sheerness Predicted sea level rise

36 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?

37 4. Sea level rise - Current/Future problems in the Thames Estuary Need to plan now…but what to do? Outer Estuary Barrier? End of estuary as we know it

38 Thank you! Keep up to date on what is happening on the Thames with:


Download ppt "How Clean is the Thames? Martin J Attrill Marine Biology & Ecology Research Centre University of Plymouth"

Similar presentations


Ads by Google