A NEW METHOD OF ESTIMATING STREAM-FLOW 
Table 40 — Dimensions of watersheds A and B 
151 
A 
B 
Total area 
222.5 acres 
7,300 feet 
1,328 feet 
9,373-11,355 feet 
200.4 acres 
4,(100 feet 
1,898 feet 
9,245-10,952 feet 
Extreme length 
Computed mean width. . . . 
The observation equations (page 152) for Stream A as used in the least-square 
solution designated as Solution M, serve as a typical illustration. This is part of 
the observation equations for that solution which included in all 242 such equations 
covering the months February, August and September 1912 and June to September 
inclusive and December 1913 — 8 months in all. 
The equations (page 152) are written in the form of equation (60) . In each column, 
the unknowns (R), (Ri), (Ri), . . . (R 10 ) should be considered as repeated down 
the column. The method of computing — D for each of these equations will be 
next illustrated, and thereafter an illustration will be given of the method of com- 
putation of r h r s , r t , . . . r l0 . 
The computation of — D, the absolute term in the above equations, was 
effected by use of equation (59) in which the following values of the unknowns were 
used: 
R" =+61 
R\ = + 0.26 
R\=+ .23 
R'\= + .15 
R\=+0.17 
R\=+1.1S 
R\=+1.05 
R"t=+ .83 
R 8 
= +0.87 
R"»a 
= + 
.314 
R" » b 
= + 
.058 
R"w 
= + 
.58 
(66) 
These values were based partly upon previous least-square solutions and were 
partly estimated. In this sense the derivation of the i2's from Solution M — and by 
equation (61), S c , R\, R'*, . . . R\o — may be considered as some multiple of the 
process stated in step (4), page 147. The table on page 153 is an illustration 
of the method of computing — D for each of the above observation equations : 
In the computation of — D, the second column and the quantities in paren- 
theses at the beginning of subsequent columns are the R'"s of (66) as shown in the 
headings of the columns. The other quantities, excepting the last two columns, 
are the r's. The last column in the left-hand member of the equations is the 
observed discharge, D', expressed in units of 0.001 c.f.s. The right-hand member 
of the equations, or last column to the right, is — D, which values are copied into 
the observation equations already presented on page 152. 
Referring to Plate 10, D' or the observed flow is shown as a solid line. 
Table 41 is an illustration of the computation of r h from which r 2 , r,, . . . r 10 
follow, according to the definitions previously given. 
In the example of computation of r h column (2) shows the mean rainfall as 
observed on Watershed A at the stations named on page 150 and shown on Plate 7; 
column (3) the mean temperature, t ; column (4) the observed mean vapor-pressure ; 
column (5) the saturation vapor pressure corresponding to t; column (6), the e of 
equation (65); column (7), 0.319 e, or that part of the evaporation from a water 
surface due to the saturation deficit alone; column (8), the mean wind movement 
over the watershed; column (9), the estimated evaporation from land by use of 
equation (65); column (10), the observed run-off in c.f.s., reduced to 0.01 inch of 
