SEEPAGE OR RETURN WATERS FROM IRRIGATION. 
47 
TABLE IX. 
TABLE FOR VELOCITY OF FLOW THROUGH PERMEABLE SOILS. 
Values of lc in formula, v=ki, for different units of time : vis 
velocity in feet; i is the inclination or fall in feet per foot. 
1 
Kind of Material. 
! Size Grains, in 
Inches. 
Voids, 
Proportion of. 
--1 
Velocity. 
Per 
Second. 
Per 
Hour. 
Per 
Day. 
Per 
Year. 
Minute Gravel. 
.08 
0.41 
.024 
86.47 
2075 
757520 
Coarse Sand. 
0.38 
.0026 
9.33 
224 
81730 
Fine Sand.. 
.008 
0.35 
.00047 
1.69 
40.5 
14777 
Sandy Soil. 
, 
0.30 
.00022 
.79 
18.9 
6897 
Sandy Clay. 
.... 
0.25 
.00012 
.42 
10.2 
3725 
0.20 
.00003 
.12 
2.8 
1035 
Clay..} 
.... 
.00008 
.295 
7.1 
2587 
Example. —What distance will water pass through coarse sand in a year, 
inclination about 1 in 100 ? 
Here i= 1-100. If the sand averages 1-10 inch diameter, without finer 
particles, it would approach what is here designated as minute gravel. In one 
year the distance would be the number 757,520 multiplied by the inclination, 
1-100, giving a distance of 7,575 feet, or about one mile and a half. If in coarse 
sand, as here termed, a distance of about 800 feet. 
If the movement is downward, then i is 1. If there is a head in addition, 
then i may be greater than 1. 
§39. An opportunity to measure the loss by seepage from a 
canal, and, indirectly, the rapidity of passage of water through the 
soil, occurred at the time of making the seepage measurements. 
The Fort Morgan canal is of considerable size. It was measured 
about three miles below the headgate. Another measurement was 
made at a point 7.4 miles from the first, at the head of the old flume 
across Bijou creek. Two small laterals between were withdrawing 
water. This was measured and taken into account. For much of 
the distance the canal skirts the bluffs between the bottoms and 
the up-lands. For part of the way the soil is very sandy. At the 
first point of measurement the canal was carrying 208.28 second- 
feet; at the second point, 183.83 second-feet. The intermediate 
laterals withdrew 4.37 second-feet. Hence the loss, including seep¬ 
age and evaporation, amounted to 20.08 second-feet. The evapora¬ 
tion from the surface, averaging forty-five feet wide, under the con¬ 
ditions of temperature of water and air cannot exceed one-fourth 
of one cubic foot per second, by use of formula in annual report 
of 1891.* 
Practically, therefore, the whole loss is seepage. This stretch 
of the canal has not been cleaned for some years, except that in 
* Annual report, Section Meteorology and Irrigation Engineering, Report 
Colorado Experiment Station, 1891, p. 51. 
