172 
A NEW METHOD OF ESTIMATING STREAM-FLOW 
when the stream-flow is as low as 0.040 c.f.s., an addition to the storage on the 
watershed of 0.66 inch is necessary to saturate the ground before any of it goes to 
the stream as surface run-off. On the other extreme, when the stream-flow is 0.400 
c.f.s. or more, only 0.20 inch increase in storage is necessary to saturate the ground 
before surface run-off begins. These values are shown plotted in the upper right- 
hand corner of Plate 22. 
EXAMPLE OF OBSERVATION EQUATIONS FOR FLOOD-FLOW, STREAM B 
One form of observation equation to determine flood-flow is equation (57). 
This was the first form used in the investigation, before any idea at all was obtained 
as to how large the R'/s would be. If it is possible to estimate values of these 
constants, it is generally more advantageous to use the following form of observa- 
tion equation for determining flood-flows: 
r /l R / i+r /t R /l +r /l R,i+r /i R /t +r / i l R /i +r /t R /t +r / ,R/, — F = v (78) 
In which F is computed from the following: 
r /1 R" fl +r fI R"n+r / ,R" / ,+ r / Jt" /t +r fi R'', i +r /i R" /s +r n R''„-F' = -F (79) 
In equation (79) R"n, R"/t, R" '/*, • • • R" n are assumed values of R' /lt 
R'fL,R'fi, . . . R' / t, respectively. —F is that part of the flood-flow not accounted 
for in terms of r n R"n, t /2 R" '/», r n R" , x , . . . r /7 R" fl . It represents the total error 
resulting from the use of the R"/s. The corrections to the R" /s to get the R'/s 
are the R/s of equation (78); that is, 
R' fi—R" f\-\-Rf\ 
K /» = tt /2 + /1/2 
R' fi = R"fi-\-R/» 
R'/i = R"/i-\-R/t 
R'/7 = R"/7-\-R/7 
(80) 
Observation equations for flood-flow, Solution K, Stream B, October 1911 
Date 
Terms of equation 
+r;iR/\ 
+r/ 2 R/i 
+ r/ 3 /?/ 3 
+ r/ t R/t 
+r/iR/i 
-r-r/sR/s 
+rjiR n 
-F = v 
Oct. 4... 
5... 
6 
+ 15/?/! 
+ 197 
+ 6=«i 
-272 = i' 2 
- 247 = j)j 
-lS9 = e 4 
-247=»j 
-303 = r 6 
- 275 = !' 7 
-214 = j) 8 
-149 = t'» 
- 105=wi(i 
-119 = ?)il 
- 88 = t>i2 
- 58 = »« 
- 41=n< 
- 26 = t)i 6 
- 13=1',6 
+ = l'ij 
+ 12 = f 18 
- 36 = 1 19 
- 27=t*a 
- 24 = !'2i 
- 14 = «M 
- 9 = Vu 
+ 15R /2 
+ 197 
+ 15/?/3 
+ 197 
7 
+ 15/P/4 
+ 212 
+ 197 
8 
9 
+ 2/? /5 
+21 
+ 21 
+21 
+20 
10 
11 
12 
13 
+ 2J?„ 
+21 
+ 21 
+ 21 
+ 21 
+ 21 
+21 
+ 21 
+ 20 
14 
15 
16 
17 
is 
19 
20 
21 
+ 2R n 
+ 21 
+ 21 
+ 21 
+ 21 
+ 21 
22 
23 
24. . 
25 
26 
