RANGE WATERING PLACES IN THE SOUTHWEST 22 
LOSS FROM SEEPAGE 
Seepage is always to be reckoned with in unlined earth basins. If 
the selected location has a good clay-grit soil, seepage will generally 
be of little importance after puddling. If, on the other hand, the 
soil is loose, porous, or soluble, the capacity of the reservoir must be 
liberally figured and special treatment to prevent seepage will prob- 
ably be necessary, perhaps making the cost excessive. Rarely do new 
reservoirs hold satisfactorily until after several months, the period 
varying greatly with the soil. 
The bottom of a new storage basin should be packed or “ puddled ” 
by livestock to reduce the loss by seepage. This may be done effec- 
tively by constructing a temporary fence around the basin to confine 
a herd of horses or cattle overnight, or by “ milling” them around in 
the wet soil for several hours. A roped inclosure will usually hold 
horses. In many cases a certain amount of silting and additional 
trampling is necessary before rapid seepage is stopped. Salt in 
small quantities placed around the water’s edge (PI. X, fig. 2) or in 
the empty basin when the soil is damp will encourage trampling. 
This should not be done as a regular thing after the bottom is prop- 
erly packed, since it encourages needless congestion of animals with 
consequent overgrazing around the water. 
EVAPORATION 
- Evaporation consumes water rapidly in the Southwest, where low 
humidity, high temperatures, and winds are common. Though it 
varies greatly for the different regions and years, the examples in 
Table 6 show that in the localities indicated evaporation from free- 
water surfaces greatly exceeded the rainfall. 
TABLE 6.—Summaries of evaporation measurements 
ee Average 
‘ : yearly yearly 
Locality Altitude | Inclusive precipi- | evapora- 
(feet) dates tation tion 
(inches) (inches) 
BlephanteButterD am) vNiy Mex eae eee 4,265 | 1919-1923 8.95 | 100. 33 (17) 
meniculturale@ ollegessN- WMiex ==) == 2-25 ees ee ee 3, 863 | 1919-1923 7. 96 92. 35 (17) 
IROOSGViCUG PAZ Rees use easement een Ne sees 2,175 1921-1923 le gal 85. 56 (11) 
Mesa xperiment Marnm, Ariz = 5222252 So ue es ee ee 1,225 | 1921-1923 TOP> io PY PAL GHD) 
CSHEVTTUE, END aN aN Us oS I i IN ee oS Se nS 7,013 | 1919-1923 15. 27 C173 2CL7) 
Water lost by evaporation is in proportion to the area of the 
water surface and is accordingly less from a deep, narrow basin 
than from a broad, shallow one. Shelter from hot, dry winds, such 
as is afforded by timber or high shady ledges, tends to reduce 
evaporation. 
GENERAL SIZE RECOMMENDATIONS 
With evaporation and seepage such important factors, volume 
should be obtained primarily by depth, next by length, and lastly 
by width of the water basin. The length and width will depend 
principally on the general contour of the country. The history of 
26 typical southwestern livestock reservoirs showed that of the 10 
