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49
Sunbury Weirs, and having entrusted this work to Mr. Middleton
and considered his report we accept his opinion that Mr.
More's quantities should be increased by 7 per cent. To the
435,931,000,000 gallons we therefore add 40,515,170,000 gallons,
making 466,446,170,000 gallons. To this again must be added
the average quantity taken by the Companies, viz., 30,896,000,000
gallons, giving a grand total of 497,342,170,000 gallons. Divided
by 365 this gives a daily average of 1,362,581,288 gallons.
Year.
Total Quantity of
Water abstracted by
the
Water Companies.
Volume of Discharge
at Teddington Weir
as, guaged by the
ThamesConservancy
Total flow of
River Thames
(Col. 2 + Col. 3.)
Ave. age Annual
rainfall on
Thames Basin
above intakes of
the Water
Companies.
Gallons.Gallons.Gallons.Inches.
1883 26,197,000,000 659,657,000,000 685,584,000,000 2841
1884 29,946,000,000 330,648,000,000 360,594,000,000 2290
1885 29,654,000,000 339,130,000,000 428,784,000,000 29· 15
1886 30,350,000,000 544,786,000,000 575,136,000,000 31· 07
1887 32,154,000,000 390,296,000,000 422,450,000,000 21·32
1888 30,280,000,000 427,656,000,000 457,936,000,000 28·45
1889 31,419,000,000 437,059,000,000 468,478,000,000 25·64
1890 32,876,000,000 261,916,000,000 294,792,000,000 22·81
189l 35,185,000,000 472,228,000,000 507,413,000,000 33·3I
Total 278,061,000,000 3,923,376,000,000 4,201,437,000,000 243· 06
Average)
ot the 30,896,000,000 435,931,000,000 466,827,000,000 27· 01
9 vears.
"During the nine years in question the rainfall averaged
only 27·01 inches as compared with 28·50 inches which Mr.
Symons gives as the mean fall of a long term upon the watershed.
We therefore increase the daily volume to 1,437,747,750
gallons, raising it in the ratio of 27·01 to 28·50 inches. This
quantity must, however, be reduced in the proportion of the
area above Teddington, viz., 3,766 square miles, to that above
the intakes, which is 3,548 square miles, thus bringing down the
nett daily quantity to 1,354,521,778 gallons. This, we believe,
is a very close approximation to the daily average flow of the
Thames down to the waterworks intakes during a long series of
years, and we will call it, in round figures, 1,350,000,000 gallons.
The average daily discharge of three consecutive dry years we
estimate at 1,120,000,000 gallons, and of the driest year at
900,000,000 gallons.