A NEW METHOD OF ESTIMATING STREAM-FLOW 155 
r 6 = 2 (ri for June 22 to 25 inclusive) ■*■ 10= — 4 to the nearest unit. 
= 2 (r« on June 26 and 28) -5-10. 
r, = 2 (n for June 14 to 21 inclusive) -5- 10 = —63-5- 10= —6 to nearest unit. 
= 2 (r» on June 22 and 26). 
The remaining r's, r 7 , r», r, and r 10 , reach back in their derivation to dates pre- 
ceding June 1913 and therefore their computation can not be illustrated. Note 
the division by 10 after r 4 . A similar division by 100 was made after r th , the object 
in both cases being to make all the coefficients in the observation equations of 
approximately the same magnitude to facilitate general checking. These divisions 
also lessen the labor in forming the normal equations, and tend to give greater 
accuracy to the derived constants. 
Referring to Plate 10, r, is shown plotted as a dotted line above or below the 
horizontal line of constant flow, S c . In the manner indicated, the change in stor- 
age on the current day was computed for Stream A for the whole period 1911-1915. 
This is shown for 1912-1915 on Plates 9 to 12 inclusive. For the change in storage 
on Watershed B (see Plates 13 to 17 inclusive) the method of computation was the 
same except that different (better) values of C, F and M were used, and a different 
rule for fixing the last date of full net melting in the spring was adopted. These 
two changes, resulting in better results on Stream B, will be discussed more fully 
later. 1 
Attention is called to the fact that the wind movement (the w of equation (65)), 
in the example of computation of r», is so small that the expression in parenthesis in 
equation (65) was never positive on the dates given, hence the estimated evapora- 
tion from water is merely 0.319 e, and from land, (0.319 e) (2.3). In fact, in the 
whole five-year period on both watersheds A and B, w was rarely large enough to 
enter into the evaporation equation as derived from observations on the Great 
Lakes. This is evidently due to the difference in elevation of the anemometers 
above the ground (or lake) surfaces in the two cases. On the Great Lakes, as 
already stated, the average elevation of the anemometers was about 100 feet above 
ground surface, whereas [on the Wagon Wheel Gap Watersheds they were about 
5 feet above the ground surface. It is believed that this condition gave rise to too 
small an estimated evaporation from water at the Wagon Wheel Gap area, and 
W 
accounts for the large value of — - of 2.3, in comparison with the 0.62 derived and 
E v 
used on the Great Lakes. 
It should be noted further that in the example given of the computation of r,, 
the net melting did not enter, because there was no snow or ice on the watershed 
available to be melted. All of the addition to storage in June 1913 occurred as 
rain. It is evident, however, from the definitions of the other r's, that net melting 
did enter into the computation of some of them. For example, some of the various 
r's in the equation for June 1, 1913, extended back, as follows: 
On June 1, 1913, ri =2 (n for September 17, 1912, to January 22, 1913, inclusive); 
r. = 2 (r, for March 29, 1913, to April 29, 1913, inclusive); 
r 7 = 2 (r, for April 30, 1913, to May 15, 1913, inclusive). 
Now, the first date in the fall of 1912 on which snow fell was about October 
30, and the last date in the spring of 1913 on which there was snow on the ground 
1 See pages 157, 192 and 198. 
