THE FREMONT RIVER.
The largest branch of this stream rises in the Un-ca-pa-ga Mountains, and after flowing in an easterly direction for 125 miles enters the Colorado about 40 miles below the junction of the Grand and Green. It is joined by one considerable tributary, Curtis Creek, from the north, and another smaller, Tantalus Creek, from the south. The lower half of its course is through two deep cañons, separated by an intervening valley called Graves Valley, in which is an area of 10 square miles of arable land, with an altitude of 4,500 feet above sea level. On the upper waters of the main river, in what is known as Rabbit Valley, and at an altitude of nearly 7,000 feet, are 25 square miles of arable land of good quality. This area, from its altitude, should be subject to late and early frosts, but the warm sandy soil and southeastern slope of the whole valley will probably prevent much damage from this cause. The valley is now used as a herd ground for cattle belonging to the settlements in Sevier Valley, and the few experiments made by the herdsmen in cultivating the soil also indicate that the danger to be apprehended is slight. The volume of water flowing through Rabbit Valley in July, 1875, was 175 cubic feet per second.
Tantalus Creek drains the northern portion of the eastern slope of the Aquarius Plateau. It enters a close cañon at 8,000 feet altitude, and continues in cañons until it has passed through Water Pocket Fold. It then flows along a desolate valley at the foot of the fold until it joins the Fremont River. During the warmer months the water in this creek is usually absorbed and evaporated before reaching its mouth. In the valley at the foot of Water Pocket Fold are about 10 square miles of arable land; but the almost inaccessible situation of the valley and the desolation and ruggedness of the surrounding country may present insurmountable obstacles to its settlement.
Curtis Creek, the northern tributary of Fremont River, is formed by the union of several smaller streams that rise in the Wasatch Plateau. Debouching from the plateau, these branches flow across what is known as Castle Valley, and here, at an altitude of 6,000 feet, are 25 square miles of good arable land. They were measured in September, 1876, and gave an aggregated flow of 47 cubic feet per second. As they derive a greater part of their waters from the melting snows on the plateau, double this amount, or 94 cubic feet, would not be an overestimate of the volume during the irrigating season. After the union of these branches, the united stream flows in a deep cañon until near its junction with the Fremont River in Graves Valley. Both Curtis Creek and the Fremont receive some accessions to their volume from springs in the cañons through which they flow above this valley. If all the water in their upper courses should be used to irrigate lands in Castle and Rabbit Valleys, a sufficient amount would be returned to their channels by percolation to irrigate, with the addition of the accessions in the cañons, all the arable land in Graves Valley.