IOP BULLETIN 1358, U. S. DEPARTMENT OF AGRICULTURE 
in the gravel of stream beds, concrete construction is best. In the 
channel where rolling bowlders are lable to crush the pipe, and 
where it crosses streams, roads, or trails, it should be well buried. If 
intended for use during freezing weather, it should be buried below 
frost danger and exposed sections at troughs packed. In some cases 
long pipe lines or those rigidly fixed at both ends should have 
expansion joints. 
WATER TRAILS 
The opening of trails is one of the ways by which watering condi- 
tions on many rough, timbered, or mesa ranges may be materially 
improved, often at small cost. Permanent water at the bottom of 
deep, cliff-rimmed canyons is often inaccessible from valuable un- 
watered range on higher mesas or ridges until trails are con- 
structed to the water. Such trails should have a reasonable grade 
and be kept clear of bowlders, so that weak animals can readily 
climb out of the canyon after drinking. Im locating such trails 
dangerous cliffs should be avoided if possible. 
WELLS 
Wells are the principal livestock water developments in many dry 
regions where natural springs and running streams are inadequate. 
(Pl. I, fig. 1.) The water supply from wells is less likely to fluctu- 
ate with local rainfall, and is consequently more dependable under 
southwestern conditions, than that from surface reservoirs. 
It is outside the scope of this publication to discuss in detail either 
the digging or drilling of wells (2). Well drilling is usually done 
by contract by parties equipped for the business. 
LOCATION OF WELLS 
One advantage of wells over other types of range water develop- 
ment is the greater leeway possible in their location with respect to 
the needs of the livestock and the range. One should endeavor to 
penetrate good water-bearing strata at the least depth possible. 
Dug wells are perhaps more likely to strike water at shallow 
depths within the immediate flood plains of washes, although the 
risk from freshet damage is great, and it is usually preferable to 
select a site near a wash, but back out of reach of floods. The avail- 
able underground water supply is very limited in certain rock forma- 
tions such as granite, and in clays and other firm soils. Under such 
conditions dug wells are usually advisable. 
Extensive underground layers of gravels and coarse sands usually 
furnish water abundantly. On plains or mesas of unconsolidated 
alluvial deposits extending back from large valleys toward high 
mountain ranges, the higher the elevation the deeper the water table, 
other things being equal. On such table-lands drilled wells ordi- 
narily will be required to reach the water table. Impervious strata 
may force water near the surface locally, however, or unsuspected 
porous areas allow it to sink to lower levels. The advice of the 
United States Geological Survey or of State or other reliable geolo- 
gists, the Judgment of reliable well drillers, and a study of existing 
wells in the neighborhood are valuable in determining promising 
