48 BULLETIN 339, U. S. DEPARTMENT OF AGRICULTURE. 
being used to make them conform as nearly as possible to standard 
curves for similar sections. After all of the measurements had been 
made, floats consisting of tightly corked bottles were dropped into 
the main canal at the upper gage, and a man proceeded down with 
them, reading each gage in the main canal and at the head of all 
diversions at the time the floats passed. Other men with more floats 
followed the first ones at 2 to 3 hour intervals during the day. The 
discharges at the different stations and the consequent seepage losses 
between were determined from the gage heights at the time the 
floats passed, thus minimizing error from fluctuations in gage 
height. This method compares losses from the same flow or wave of 
water for a 12 or 14 hour period, and while the rating curves based 
on only two points may be slightly inaccurate, the canals were held 
quite uniform throughout the entire investigation. 
The larger canals were measured either from cars which were 
suspended from cables across the stream or from a boat especially 
fitted up for the purpose (PI. III, fig. 2). The smaller canals, where 
convenient bridges could be found, were rated from the bridges, and 
in other cases, where the depth permitted, wading measurements 
were made. 
There are two common methods of expressing seepage losses. One 
is per cent of flow lost per mile, and the other the number of cubic 
feet lost from each square foot of wetted canal bed in 24 hours. The 
former and older method is more readily calculated and understood, 
but since the percentage decreases rapidly as the capacity is increased, 
many prefer the use of the latter unit, as it is more constant for any 
type of soil and largely independent of the capacity of the canal. 
Table XXIV gives the results of measurements of seepage losses. 
For convenience, the losses are expressed by both methods. 
TABLE X XIV.—Seepage losses from canals. 
i Loss 
Aver- Dis- 
g€ | Area | Wet-| charge Total ene 5 eee 
width| ater | ted at loss eaae Loss oe ae Loss 
No f sur. | Per | upper in aaa per |vettea| Per Remarks. 
water im- | end of] sec- mile mile 
face b- area 
sur eter sec- tion served er 24 
face tion ; eee 
Square Second-| Second- Second-| Cubic Per 
Feet.| feet. | Feet.| feet. feet. Miles.| feet. feet. cent. 
: o 9 0.12} 1.0 0.07 0.02 | 0.490 0.04 | 0.666 57.1 | Medium clay loam. 
0 eal Gn elise 14 02 399 05 . 684 Soa Do. 
Ou |e: eal OU nets 20 04 . 700 . 06 . 623 30.0 | Deep clay Ioam. 
: ae : a2 i . 28 - 08 . 682 S12) 1. 129 42.9 Clay loam, gravel. 
; : ; 36 - 08 .379 -21 | 1.919 58.3 0. 
Gn -48 | 1.9 53 -07 .714 -10 . 844 18.9 | Clay loam, hardpan. 
C2 260 Ss i| ise! 54 07 740 10} 1.107 18.5 | Deep medium clay loam. 
Sale 22h aeleG 58 03 .378 .08 811 13.8 | Shallow clay loam. 
9 | 1.8 SS 98} 68 03 . 469 06 455 8.8 | Impervious clay loam. 
0 ry : = 2} 0 13 528 .25 | 1.919 31.3 | Medium clay loam. 
: BSO : 03 . 422 01 659 4.3 Do. 
2 a ee a2 2 a 435 28 | 2.052 32.9 Porous sae clay loam. 
. a : 7 -573 07 714 8.0 eep clay loam. 
14 | 3.5 ol! SS 99 07 519 14 596 14.1] Clay loam, hardpan. 
