158 
SNAKE RIVER PLAINS OF IDAHO. 
[BULL. 199. 
Water flowing through an inclined pervious hod meets with resist- 
ance due to friction of flow. If the pervious bed is included between 
two impervious beds, as, for example, in the ideal section shown in tig. 
6, and a hole is drilled from the surface down to the water-charged 
layer, as at x, the friction of flow between x and g, 
where the water naturally escapes, may be sufficient 
to retard the current and cause the water to rise in 
the hole and possibly overflow. The reason is simply 
that the resistance met by water rising in the hole 
drilled at x is sufficiently less than the resistance 
between ,/• and g to permit it to rise to the surface. 
The moving force in this instance, as in an artesian 
basin, is hydrostatic pressure. This matter has been 
discussed in the report on Nez Perce County, refer- 
red to above, where reference to other papers on the 
same subject may be found. 
In the case of an artesian basin the pervious layer 
is essentially a filled reservoir, and the water is at rest 
until an opening is made in drilling a well; in the arte- 
sian slope the water is (lowing. These statements, to 
be smc, need to be qualified to be strictly accurate, 
but they express the leading difference referred to. 
The success of wells drilled so as to tap an artesian 
slope depends not only on the quantity and perma- 
nence of the water supply, but on the degree of resist- 
ance the water meets with in passing through the 
permeable stratum. The greater the resistance within 
certain limits, the higher the water will rise in wells 
leading to the surface. 
It is not to be understood that all of the various 
ways in which subterranean water may be brought 
under pressure so as to be available for artesian wells 
have been enumerated. On the contrary, the only 
attempt here made, is to cite certain well-known 
principles for use later. 
I 
AVAILABLE 
WATER ON 
PLAINS. 
SNAKE RIVER 
The most serious economic problem which con- 
fronts the people of southern Idaho is how to obtain 
water for irrigation and for tow T n and household pur- 
poses. The soil is almost universally of good qual- 
ity, level land that could be easily tilled is abundant, 
the sunshine is brilliant, the temperature favorable, but the critical 
Fig. 6.— Section of an 
artesian slope. 
