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197
this will demand the utmost vigilance from the P.L.A. and all the
available skills of the G.L.C.'s Scientific Branch.
Success will lie mainly in abating, at source, all pollutants which
are unlikely to be rendered harmless by natural processes, particular
attention being paid to the most recent form of pollution,
namely, that arising from the surreptitious discharge of waste
oils during the hours of darkness by unscrupulous tanker captains.
For this, co-ordination of all authorities responsible for
controlling pollution in rivers and watercourses will be necessary
so that such waters are made capable of supporting fauna
essential for sustaining sea fisheries and allowing passage of
migrating fish at all states of the tide.
In an interesting and independent development, a manufacturer
with a riparian factory has, during the year, introduced an
aerating process which dissolves oxygen into the river equivalent
to the bio-chemical oxygen demand load of its effluent discharged.
Such a responsible and co-operative action warrants replication
by all industries producing effluents calling for a high oxygencontaining
medium for their satisfactory degradation.
Rainfall, although modified by industrial discharges, exerts the
greatest influence upon the quality of river water and, as one
would expect, the higher the rainfall the more able is the river to
stand pollutants. During 1971, total rainfall at 563.0 mms. was
some 9.5% less than that for 1970 and 13.4% lower than the
average for the previous 6 years. Nevertheless, no complaints
regarding pollution were made to this Directorate during the current
year.
Storm Flooding
As with 1970, no storm flooding occurred during the current
year and consequently, in this respect, no requests for assistance
were received.
Flood dangers arising from a combination of unusually heavy
rainfall and abnormally high "spring" tides will be appreciably
lessened when the scheme to introduce a "flood barrier" in the
Woolwich Reach is implemented. Such conditions are likely to
occur only once in every 200 years, meanwhile the G.L.C.'s
interim measures to raise the height of the river wall are proceeding
to prevent a repetition of the catastrophes of 1928 and 1953.
ATMOSPHERIC POLLUTION
Conversion of energy from one form to another is a characteristic
of all life. With man, who has learned how to release stored
energy from fossil fuels to modify his local environment, this is