188 A NEW METHOD OF ESTIMATING STREAM-FLOW 
EXAMPLE OF COMPUTATION OF z„. SOLUTION AA, STREAM A 
The definition of z„ is given by equation (54). It consists of the known quanti- 
ties R\, R\, R'„ ... and {t-T"), 2 2 (t-T"), X t (t-T") . . . , in which t>T" 
and there is an abundance of snow and ice on and in the ground of the watershed 
available for melting. The last quantities are first computed from the mean ob- 
served air temperature over the watershed, t, and T" = 28° F., and then multiplied 
by the R"s of equation (76). The sum of the products gives z n . This is illustrated 
as shown on page 189. 
The quantities in parentheses are values of (t-T"), V^t-T"), 2 3 (t-T") 
. . . , restricted to days on which t > T", and on which there is an abundance of 
ice and snow on and in the ground available for melting. The units are the same 
as in the computation of y n . After computing (t-T"), the other parenthetical 
values were computed from it as in previous analogous computations. The quan- 
tities not in parentheses, at the heads of the columns are the.R"s of equation (76). 
They should be considered as repeated down the column. The sum of the products 
2 (t - T")R' gives z„. The unit of the products R"L (t - T") M is in 0.001 c.f .s. The 
rounding off of the numerical quantities is done as in the case of y n . 
Previous to March 31, there being no flood-flows, z n = z, the coefficient of M in 
equation (46). From March 31 on, z = z„-\-Z;. The illustration of the computation 
of z f follows. 
EXAMPLE OF COMPUTATION OF Z / AND z, SOLUTION AA, STREAM A 
The definition of z, is given by equation (55). It consists of the known quanti- 
ties R' ,„ R' n , R'n, ... and (t-T"),2 2 (t-T"),2 3 (t-T") . . . , confined todays 
affected by flood-flows, as in the case of x f , and days on which there is an abundant 
supply of ice and snow on and in the ground available for melting. The quantities 
(I — T") and their sums are first computed for the same days decided upon in the 
computation of (n 1 — Gi) and their sums, and then multiplied by the R' /s of equa- 
tion (87). This is illustrated on page 190. 
The quantities in parentheses are values of (t — T") and their sums, restricted 
to days affected by flood-flows and on which there is an abundance of ice and snow 
available for melting. The units are the same as in the computations of y n and z n . 
The quantities not in parentheses, at the heads of the columns, except the last three 
columns, are the R' /s of equation (87). The sum of the products 2(t — T")R' , 
gives z,. In evaluating z,, the quantities are rounded off as previously described 
for y n . The unit of the products R' £{t-T")M is 0.001 c.f.s. The last column but 
one contains z n copied from page 189. The last column, z, is the sum of the two 
preceding ones. 1 It is the coefficient of M in equation (46) on days affected by 
flood-flow. 
This completes the illustrations of the computations of all the known quantities 
in equation (42) and the combining and grouping of them as far as possible to get 
them into the form of equation (46) according to equations (43) to (45) and (47) 
to (55) inclusive. The next step is to write out the observation equations for the 
1 By Eq. (49), page 143. 
