Ratio of Maximum to Minimum Stream Discharge 
The ratio of maximum to minimum stream discharge is an indicator of 
the water storage function and of change in hydrologic characteristics 
of the watershed following change in land use. The ratio of maximum 
to minimum streamflow has generally been found to be larger for dis- 
turbed or denuded areas than for undisturbed areas (13). As an illus- 
tration, in the Wagon Wheel Gap experiment it was found that before 
denudation the ratio was 12:1, and after cutting it was 17:1. This 
ratio varies widely between streams according to many factors. In 
some cases the ratios are narrow, while in other cases the ratios are 
wide. 
10/ 
A determination has been made of the ratio of maximum to minimum flow— 
for all streams. The ratio is generally based on maximum l-day flood 
and minimum l-day flow. However, 5 inches of rain fell within 24 hours 
on October 13, 1949. This resulted in an extremely high stream dis- 
charge rate which greatly distorted the ratio. Median values of 
maximum 1-day flood discharge and minimum 1-day flow were found to be 
more realistic. Median values, instead of absolute values, will there- 
fore be used in comparisons between pre-logging and post-logging periods. 
The ratios of median values of maximum 1-day flood and minimum 1-day 
flow vary between 42:1 and 152:1 for Harris River, Maybeso Creek, and 
Indian Creek (table 6). This ratio cannot be shown for Old Tom Creek 
because a discharge rating curve has not been developed as yet. 
Table 6.--Ratio of maximum/minimum stream discharge, May- 
October, 1949-1953 
: Median value : Median value 
Stream : maximum l-day : minimum l-day : Ratio 
flood : flow : 
Gries. Cnr S 
Maybeso Creek 802 17 47:1 
Harris River 1,250 30 42:1 
Indian Creek 456 3 52 icek 
10/ a. The maximum 1-day flood is defined as the highest average rate 
of discharge for any l-day between May and October, inclusive. 
b. The minimum l-day flow is the lowest average flow for any l-day 
between May and October, inclusive. 
c. The median l-day flood is the median value of the maximum l-day 
floods between May and October, 1949 to 1953, inclusive. 
d. The median 1-day minimum flow is the median value of the minimum 
l-day flow between May and October, 1949 to 1953, inclusive. 
EDI = 
