10 BULLETIN 198, U. S. DEPARTMENT OF AGRICULTURE. 
from the gaugings. The formula was changed and the investiga- 
tions continued until a satisfactory curve was obtained. 
After an examination of the results of the gaugings heretofore 
described, taking into consideration the probable effect that the 
reclamation of the district will have on the rate of run-off/ and after 
a study of some of the larger drainage districts in the immediate 
vicinity of the Cypress Creek drainage district, the following tenta- 
tive assumptions were made as to run-off: 
From 5 square miles, 1 inch in 24 hours (26.88 second-feet per square 
mile) ; from 25 square miles, f inch in 24 hours (20.20 second-feet per 
square mile) ; from 400 square miles, i inch in 24 hours (13.44 second- 
feet per square mile) . 
It was found that Farming's formula could be converted into an 
expression whose curve fulfilled these assumptions. The conversion 
of this formula is as follows : 
Fanning' s formula is: # = 200 M* 
Where Q = run-off from whole area, in second-feet, 
and M= area of watershed, in square miles. 
Substituting If for 200, and R M for Q (where R = the run-off in 
second-feet per square mile), we have: 
BM-UfiorB-Zj*--*! (1) 
whence K=RyM 
Substituting the three assumed values of R and M, we have: 
Fori? = 26.88, Z=35 
Fori? = 20.2, Z=34.5 
Fori? = 13.44, Z=36.4 
Replacing the constant, K, by 35 in formula (1), we have: 
H -y~m 
This expression, which has been used for calculating run-off in this 
project, is represented by the curve in figure 5. It was found to 
agree fairly closely with what gaugings have been made, giving in 
most cases values somewhat greater than the gaugings showed. 
As has been pointed out, however, overflow and backwater affected 
some of the gaugings and tended to give discharges less than the 
actual ones. Allowance has also been made for increased run-off 
to be expected after drainage. 
DRAINAGE PLANS CONSIDERED. 
Before the final plan, as hereafter stated, was decided upon, other 
possible methods were carefully worked out and compared. 
