32 
A NEW METHOD OF ESTIMATING STREAM-FLOW 
elevations of the water surface at Harbor Beach and St. Clair Flats Canal, respec- 
tively, in feet above mean tide at New York. The third column shows I 4 computed 
from equation (6), by simple substitution, to the nearest 0.001 foot. The extreme 
range in 7 4 for Lake Michigan-Huron for the days used in this investigation was 
from 0.011 to 0.014 foot, with the value 0.013 foot predominating in frequency. 
Table 13. — Compulation of It, Lake Michigan-Huron 
Date 
Water levels at Harbor 
Beach, H' 
579. +ft. 
Water levels at St. Clair 
Flats Canal, h. 
575. +ft. 
Discharge of St. Clair 
River (7 4 ) 
1910 
Sept 1 
1.24 
1.19 
1.26 
1.15 
1.17 
1.34 
1.55 
1.34 
1.27 
1.30 
1.34 
1.31 
1.27 
1.23 
1.21 
1.41 
1.13 
1.21 
1.26 
1.02 
1.08 
.77 
.95 
1.10 
.96 
1.24 
1.08 
1.06 
1.40 
1.25 
.86 
1.01 
1.19 
1.39 
1.25 
1.13 
1.40 
1.13 
0.40 
.45 
.44 
.47 
.52 
.50 
.46 
.46 
.42 
.45 
.44 
.40 
.38 
.39 
.38 
.37 
.37 
.36 
.35 
.36 
.34 
.33 
.30 
.36 
.28 
.28 
.29 
.25 
.27 
.28 
.26* 
.25* 
.27* 
.33 
.29 
.29 
.36 
.38 
.34 
.38 
12* 
12 
12 
13 
12 
12 
12* 
13 
13 
13 
13 
13 
13 
13 
13 
12 
12 
13 
12 
12 
13 
12 
12 
12 
12 
12 
12 
13 
12 
12 
13 
13 
12 
12 
12 
13 
12 
12 
13 
12 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 \ 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
Oct. 1 
2 
3 
4 
6 
6 
7 
8 
9 
10 
Interpolated values or partially uncertain values due to a few hours of record on which daily mean depends 
being missing. 
The computation of h for Lake Superior is the same as that of the computation 
of I 3 for Lake Michigan-Huron, except that equation (4) was used instead of 
equation (3), to take account of the difference in lake area. 
EXAMPLE OF COMPUTATION OF h. LAKE MICHIGAN-HURON 
The definition of 7 2 is given on page 9, and the factors for use in computing it 
for Lake Michigan-Huron are shown in Table 3. The rainfall stations listed in this 
table are shown on Plate 1. In Table 14 is shown in detail the computation of h 
