INLAND WATER SURVEY 405 
In steam-driven stations the water in use in the steam cycle is used over 
and over again with an addition of from 2} to 5 per cent. to make up for 
leakage and other losses. 
The amount of circulating water required varies with the design and 
layout of the station. Under existing conditions of load factor, approxi- 
mately 60 gallons are required per unit generated, and the total quantity 
used by authorised undertakers (including oil- and gas-driven stations, 
using about 4:5 gallons per kw. of plant in operation) is equivalent to 
something like 300 million gallons (one and one-third million tons) per hour 
for 3,060 hours, or a total of over 4,000 million tons in the year. For every 
ton of coal consumed in these stations about 500 tons of circulating water 
is needed. 
In this connection steam-driven generating stations may be classed under 
three heads, viz. :— 
(1) Those using tidal water, like Battersea and Barking (where 22 million 
gallons per hour may ultimately be handled), which are only limited by the 
size of the intake tunnels and pumps. 
(2). Those using river or canal water ; and 
(3) Those with a limited supply from wells or other sources and having 
cooling towers so that the circulating water may be used over and over 
again. In this case from 3 to 5 per cent. is lost in evaporation. 
With a single station ultimately handling up to 22 million gallons per 
hour, the provision of an adequate supply of water is of first importance, 
and this accounts for the fact that all large new stations are either placed on 
a river bank or within reach of tidal water. 
In the annual questionnaire sent out by the Electricity Commissioners to 
all electricity supply authorities, those with generating stations are requested 
to state, under the sub-heading ‘ Condensing Facilities,’ (i) the source of 
water supply (stating whether tidal water, non-tidal river, canal, etc.) :— 
(a) Minimum dry weather flow in gallons per hour. 
(5) Normal usable flow at other times in gallons per hour. 
This information, though not complete, is therefore available in respect of a 
large number of stations. ‘The flow of many of the rivers has been measured 
from time to time, and a list is available giving details of flow in respect of 
fifty rivers in England and Wales and the method of gauging at thirty-seven. 
Unfortunately, in many cases very rough-and-ready methods have been 
employed and some strongly conflicting results obtained. A few have been 
measured with some degree of accuracy, but none over any extensive period 
of years. While the results on the whole may not be of much value, they 
will serve to show what has been done. 
One of the most careful and accurate measurements made was on the 
Severn at Ironbridge by the West Midlands Joint Electricity Authority, 
and details of this survey are given at the end of this memorandum. The 
Severn Navigation Board also gauged the Severn at Worcester and could 
no doubt supplement the information given here. 
Some of the rivers have been gauged at several points—the Irwell, for 
example, at five different places—and some others at two or three ; among 
the latter the river Aire, which has been gauged at Bradford, Leeds and 
Ferrybridge. When the Bradford Corporation Station at Esholt, on the 
Aire, was under consideration, the City Electrical Engineer, Mr. Thomas 
Roles, had gauging records of the flow taken from 1917 to 1921 (see details 
attached). Upstream from the power-station site the river had been 
impounded many years ago for supplying water power to a factory, and 
the dam wall was adapted by Mr. Roles for the construction of a weir 
115 ft. long and 12 in. deep, and a flute chamber some io ft. upstream 
