122 LANDS OF THE ARID REGION OF THE UNITED STATES. 
the north margin, passing out by a narrow defile at the southwest corner. 
At one time in the history of the prairie the Provo flowed northward 
through it and joined itself to the Weber. The surface of the prairie was 
then lower than now, and the sand and gravel which the river brought 
from the mountains accumulated upon it. Eventually the Provo built its 
alluvium so high that its water found a new passage over the wall of the 
valley. The new channel, affording a more rapid descent than the old, 
quickened the current through the valley, and caused it to reverse its action 
and begin the excavation of the material it had deposited. So long as the 
river built up its bed, its channel was inconstant, shifting from place to 
place over the whole plain;. but so soon as it began to cut away the bed, 
its position became fixed and the plain was abandoned. The river now 
flows in a narrow valley of its own making, 150 feet below the surface of 
the plain. As a result of this mode of origin, Kamas Prairie slopes uni- 
formly from the Provo to the Weber, and it would be an immense under- 
taking to irrigate it with the water of the Weber. But the Provo River 
can be returned to its ancient duty with comparative ease. A few miles 
of canal will suffice to carry its water to the upper edge of the plain, and 
thence it can be led to every part. Already a small canal has been con- 
structed, and its enlargement may convert the whole prairie into a meadow. 
Thus the prairie, although part of the drainage basin of the Weber, belongs 
to the irrigation district of the Provo. 
The Provo next follows a narrow rock bound valley for 7 miles, being 
skirted by bottom lands that admit of some farming. It then enters Provo 
Valley, an opening about as large as the last, and favored by a warm 
climate that permits the growth of breadstuffs. Thence to Utah Valley 
it follows a deep, close canon. j 
The volume of the Provo is sufficient to water about 100 square miles. 
If it be permitted to serve 28 miles in Kamas Prairie and 40 miles in Provo 
Valley and its adjuncts, there will remain for Utah Valley the quota for 32 
miles. The minor streams of the valley, American Fork, Spanish Fork, 
Hobble Creek, Payson Creek, ete., will irrigate 120 miles, making a total 
of 152 square miles supplied with water. The total land of the valley 
which might be irrigated if the water were sufficient amounts to no less 
than 225 miles. 
