IRRIGABLE LANDS OF THE COLORADO DRAINAGE 161 
These streams all rise in high mountains, from whose summits the snow is 
never completely melted. The line of highest water is usually in June, 
but the flow is well sustained through July. After that the volume 
rapidly decreases, and lowest water occurs in October. The critical period 
in the irrigation of this basin would occur in August. I think it may 
safely be assumed that the measurements of the Duchesne and the Uinta 
represent the flow at the critical period, but that Lake Fork should be 
doubled. This would give 1,825 cubic feet per second, or enough to irri- 
gate, at the assumed standard, 285 square miles, or 22 per cent. of the 
whole area of the basin, and indicates the Uinta drainage as one of the best, 
if not the best, agricultural valley in Utah. 
ASHLEY FORK. . 
This stream is the most northern tributary of the Green River south 
of the Uinta Mountains. It rises in that range, but at a lower altitude 
than the branches of the Uinta, and has a southeasterly course 48 miles in 
leneth. On its lower course, at an altitude of 5,500 feet, are 75 square 
miles of arable land of excellent quality, a few acres of which are now 
cultivated. There is sufficient water in the stream during the critical 
season to irrigate 25 square miles. 
HENRYS FORK. 
But a small portion of the valley of Henrys Fork lies within the 
Territory of Utah, but this portion includes its best lands. A beautiful 
natural meadow is here found, affording a large quantity of hay to the 
ranchmen of that country. The altitude is great, the valley being 6,000 
feet above the level of the sea, and hence lable to late and early 
frosts. 
About 10 square miles can be redeemed by irrigation. ‘The volume 
of the stream is sufficient to irrigate a much larger tract, but a part is needed 
for other lands which lie farther up the river, within the Territory of 
Wyoming. 
THE WHITE RIVER. 
The White River enters the Green from the east, about two miles 
below the mouth of the Uinta. This stream rises in Colorado, and has only 
21 ARB 
