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RANGE WATERING PLACES IN THE SOUTHWEST 19 
| Two boards are usually required for the bottom if a trough is 20 
inches or more wide; these boards should be beveled or mortised for 
joining with the sides. The joints, or if possible the whole trough, 
should be painted. Knots should be painted and covered with tin. 
A simple V-shaped trough is commonly used on sheep ranges. (PI. 
DX, fig. 1.) 
Galvanized troughs combine hght weight, moderate cost, and 
é Ts 
- durability, and are widely used. When properly constructed with a 
firm foundation and plenty of reinforcement, troughs of concrete are 
the most durable of all, provided damage from freezing is pre- 
_yented. Circular steel troughs (Pl. LX, fig. 2) are very durable and, 
_ although expensive, have proved very satisfactory in handling large 
numbers of cattle. A hole flush with the bottom of all troughs 
should be provided for draining. 
Troughs should be low enough to allow comparatively small ani- 
mals to drink. Ordinarily the top should not be higher than 16 
inches above the ground for cattle and 8 to 10 inches for sheep. 
Troughs should be located in a well-drained place free from 
bowlders, as easy of access as possible, and placed on a substantial 
foundation of rocks, cement, or logs. To prevent the formation of 
 mudholes, broken rocks mixed with sand or gravel should be pounded 
-around the trough and the overflow carried, preferably by a pipe, 
» away from it. For the same reason and to avoid waste of water a 
float valve is necessary where troughs are filled from storage reser- 
voirs. The float. valve should be located in a separate box of sub- 
stantial construction, or partitioned off and protected by a cover if 
in the trough itself. 
Troughs hght enough to be moved or turned over by stock should 
be firmly staked down or otherwise anchored in place. This is espe- 
cially important where they are placed in series, each filled by the 
overflow of the one above, and where a shift in position of any in the 
series may break the overflow connection. Much water will be 
wasted unless such connections are carefully made. Small open 
V-shaped metal strips are less apt to clog with trash and are more 
_ satisfactory than sections of pipe. 
RESERVOIRS OR “TANKS ” 
Where the cost of wells is excessive. the chances for striking ade- 
_ quate flows uncertain, or the economic limit of water development by 
wells and springs has been reached, dams and reservoirs (Pl. I, 
fig. 2) are practicable in many instances. Some of the larger reser- 
voirs retain water for years and furnish the only water for livestock. 
As a rule, however, their supply is of a temporary nature, and they 
are used to supplement more lasting supplies. They require less 
attention than most wells and as a rule are much cheaper, although 
some large tanks cost as high as $15,000. 
Two classes of reservoirs or “tanks” are common: (1) Those 
made by building dams across a channel, and (2) those located at 
one side of or between main drainage lines and filled by diversion 
ditches or pipe lines. Although the diversion-ditch type of con- 
struction is strongly favored in some localities, it is not extensively 
used in the Southwest. The majority of the reservoirs in the region 
are located in the channel, largely because of less need of frequent 
