SEEPAGE OR RETURN WATERS FROM IRRIGATION. 
55 
The question needs to be left open for future information. 
But the result, however, shows that the gain from the natural un¬ 
derground drainage cannot be much at best, and is probably noth¬ 
ing, at least too small to be measured. 
The rainfall given in Table X. as the average for the given 
water-shed is derived from observations taken at stations on or 
close to the water-shed. It may be considered as a fair average of 
the amount falling upon the area draining into the channel. 
As the stations are few in number and the records not complete, the 
amounts are approximations of varying degree of reliability. 
The drainage areas have been determined with a planimeter 
by measuring the area tributary to each stream from a map pub¬ 
lished by the Post-Office Department. They show the extent of 
the area tributary through these dry streams. Were the run-off in 
the course of a year equivalent to a depth of only 1.4 inches over 
the water-shed, each 1,000 square miles would give an average flow 
of 100 cubic feet per second ; or, a run-off of a depth of one inch in 
a year, from the basin of the Bijou, would give a constant discharge 
of 100 cubic feet per second. 
A calculation by aid of Table IX. shows that the amount de¬ 
rived from the inflow from these streams must be small. The 
breadth and depth of the beds of sand are unknown. If we 
assume a bed 80 rods wide and 1 thick, or an area in cross-section 
of one-half acre, and a fall of thirty feet per mile, then from Table 
IX. the velocity may be expected to be from 2 to 8 feet in 24 hours. 
As this is the flow through the interstices of the soil, which are one- 
third only of the section of the sand layer, the whole amount cor¬ 
responds to from 1 to 4 acre-feet in 24 hours, or to a constant flow of 
less than 2 cubic feet per second. 
It is not surprising that the measurements do not show any 
decided gain from such sources. 
TABLE X. 
INCREASE OF RIVER AT MOUTHS OF STREAMS. 
(The negative sign indicates a loss.) 
1 1 
Gain of Platte, 
1895. 
1 1 
® 0) 
rainage Area. 
Square Milei 
verage Rainfal 
Inches. 
Gain of Platte, 
1894. 
Second-feet. 
1 
o. of Miles B( 
tween Measur 
ments. 
Gain per Mile 
1894. 
o. of Miles B 
tween Measur 
ments. 
Gain per Mile. 
1895. 
P 
< 
Z 
Box Elder creek. 
627 
12.7 
-51.05 
3 
—17.02 
-35.27 
4.5 
—8 
Crow '• . 
1,443 
536 
11.5 
Lone Tree “ . 
11.5 
12.16 
1.5 
8.11 
114.2 
3.5 
33 
Lost “ . 
890 
Kiowa ** . 
470 
16.3 
5.26 
3. 
1.72 
—34.16 
9 
—3.8 
Bijou “ . 
. i 
1,425 
14.5 
—45.43 
5.92 
2.8 
9.8 
—16.2 
- 0.60 
—3.97 
4 
—1.00 
Pawnee “ . 
600 
.... 
3..52 
1.75 
2.01 
• • • • 
• • • • 
• • • • 
Cedar “ 
514 
9.71 
1.5 
6.5 
Lodge Pole “ . 
2..500 
iii 
—47.6 
9.5 
—5.01 
