Geoscience Reference
In-Depth Information
Case study
THE RIVER THAMES THROUGH LONDON: WATER QUALITY CHANGE
The River Thames as it flows through London is
one of the great tourist sights of Europe. It is an
integral part of London, not just for its scenic
attraction but also as a transport route right into
the heart of a modern thriving city. The river
has also a large part to play in London's water
resources, both as source of drinking water and a
disposal site for waste.
London has a long history of water-quality
problems on the Thames, but it has not always
been so. Prior to the nineteenth century domestic
waste from London was collected in cesspools and
then used as fertiliser on agricultural land (hence
the use of the term 'sewage farm' for sewage
treatment stations). The Thames maintained a fish
population, and salmon from the river were sold
for general consumption. With the introduction
of compulsory water closets (i.e. flushing toilets)
in 1843 and the rise in factory waste during the
Industrial Revolution, things started to change
dramatically for the worse during the nineteenth
century. The majority of London's waste went
through poorly constructed sewers (often leaking
into shallow aquifers which supplied drinking
water) straight into the Thames without any form
of treatment. In 1854 there was an outbreak of
cholera in London that resulted in up to 10,000
deaths. In a famous epidemiological study Dr
John Snow was able to link the cholera to sewage
pollution in water drawn from shallow aquifers.
The culmination of this was 'the year of the great
stink' in 1856. The smell of untreated waste in
the Thames was so bad that disinfected sheets
had to be hung from windows in the Houses of
Parliament to lessen discomfort for the lawmakers
of the day. In the best NIMBY ('not in my back-
yard') tradition this spurred parliament into action
and in the following decade, radical changes were
made to the way that London used the River
Thames. Water abstraction for drinking was only
permitted upstream of tidal limits and London's
sewage was piped downstream to Beckton where
it was discharged (still untreated) into the Thames
on an ebb tide.
The result of these reforms was a radical
improvement of the river water quality through
central London; but there was still a major prob-
lem downstream of Beckton. The improvements
were not to last, however, as by the middle of
the twentieth century the Thames was effectively
a dead river (i.e. sustained no fish population
and had a dissolved oxygen concentration of zero
for long periods during the summer). This was
the result of several factors: a rapidly increasing
population, increasing industrialisation, a lack
of investment in sewage treatment and bomb
damage during the Second World War.
Since the 1950s the Thames has been steadily
improving. Now there is a resident fish population
and migratory salmon can move up the Thames.
This improvement has been achieved through an
upgrading of the many sewage treatment works
that discharge into the Thames and its tributaries.
The England and Wales Environment Agency has
much to do with the management of the lower
Thames and proudly proclaims that the Thames
'is one of the cleanest metropolitan rivers in the
world'. How realistic is this claim?
There is no doubt that the Thames has been
transformed remarkably from the 'dead' river
of sixty years ago into something far cleaner, but
there are two problems remaining for the man-
agement of the Thames through London, and for
one of these nothing can be done.
•
The Thames is a relatively small river that does
not have the flushing potential of other large
rivers; therefore it cannot cleanse itself very
easily.
