INLAND WATER SURVEY 425 
Aqueduct being the same as that of the fixed gauge beside it. On the 
Aqueduct gauge the reading of the lowest water-level recorded is 9°4 ft., 
corresponding to a discharge of 290 cusecs. Other extreme readings are :— 
Highest recorded level, 24‘5 ft. corresponding to a discharge of 17,000 
cusecs. 
Highest summer level, 21:7 ft. corresponding to a discharge of 12,400 
cusecs. 
Lowest winter level, 10-15 ft. corresponding to a discharge of 710 cusecs. 
2. Two meters are used for measuring discharges, an Amsler propeller- 
type meter, and the small Price bucket-type meter. In each case, velocities 
are measured at intervals of 1 ft. vertically in planes ro ft. apart horizontally. 
The Amsler meter is always used on a rod operated from a flat-bottomed 
punt. The punt is located and kept stationary by two wire cables, bow and 
stern, anchored to the banks, and the rod held over the side. 
The Price meter is always used suspended from a cable slung between 
two permanent steel standards fixed on either bank. Raising and lowering 
and traversing the meter are accomplished by means of two winches, one 
on either standard. A full description of this apparatus, and of the method 
of using it, will be found in a paper entitled ‘River Gauging’ by M.A. Hogan, 
Ph.D., and published by the Department of Scientific and Industrial 
Research. 
Except close to the banks, and in conditions of extreme low flow, the 
velocities of water at the gauging site always exceed about ? ft. per sec., 
and no attempt is made to measure velocities below # ft. per sec. 
Occasional measurements of surface velocities are made with wooden 
floats 3 in. square and 1 in. thick, their paths being determined by 
readings from two theodolites on the tow-path. 
The field book contains five columns, Distance (from a fixed point on 
bank), Sounding, Depth of Meter, No. of Revolutions (of meter) and Time. 
The corresponding velocities are subsequently determined from the meter’s 
rating curves—which are checked from time to time in the College Labora- 
tory—and the discharges are worked out graphically, by plotting cross 
sections of the river and the velocity-depth’ curves at each ro ft. vertical. 
Corrections are applied, if necessary, for alteration of the water-level during 
gauging, and for down-stream sag of the meter’s suspending cable. 
Up to the present, some eighty-five gaugings have been made on about 
fifty different occasions during the last eleven years. It is hoped that it 
will shortly be possible to compare the results with measurements of the 
discharge made at Lincomb Weir, some four miles further down the river. 
(Diagrams have been made showing the section of the river at the gauging 
site, a typical annual hydrograph, and a drawing from which the results of a 
gauging were calculated.) 
APPENDIX F (5). 
THAMES CONSERVANCY. 
NoTEs ON GAUGING. 
By G. J. GRIFFITHS. 
Current Meter Gauging .—A straight uniform section of the river is selected, 
usually 100 ft. in length, and carefully cross-sectioned at both ends and in 
the middle. Wires are spanned across the river at each cross-section, 
divided into 10 ft. intervals or compartments. 
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