This stream enters the Colorado next north of the Paria. It rises under the wall forming the eastern face of the Aquarius Plateau; flows first northeast, then east, and finally southeast, before reaching the Colorado. Its length is 90 miles, the lower three-fourths being in a narrow cañon having vertical walls ranging from 900 to 1,200 feet in height. Through this gorge the river sweeps, sometimes filling the whole space from wall to wall; sometimes winding from side to side in a flood plain of sand, and always shifting its bed more or less with every freshet. Not an acre of accessible arable land is known in the whole length of the cañon, and its depth precludes the possibility of using the waters of the river on the lands above. Near the head of the southern branch of the Escalante, in what is known as Potato Valley, and at an elevation of about 5,000 feet, is an area of about 6 square miles of available land. The flow of water in this branch was 90 cubic feet per second in July, 1875. A portion of this area is now under cultivation, and is said to produce good crops. A portion of the east flank of the Aquarius Plateau is drained by a number of creeks that join the Escalante in the deep gorge below Potato Valley; but they all enter close cañons, in which no areas of arable land are known at an altitude low enough for successful cultivation. Part of the waters of these creeks might be used to irrigate grass lands at an altitude of about 8,000 feet; but the conditions of pasturage are such in this region that the amount practically available is small.
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.
THE SAN RAFAEL RIVER.
This stream flows in an easterly course, and enters the Green 32 miles above the junction of that stream with the Grand. It has three principal branches—Ferron, Cottonwood, and Huntington Creeks—all rising in the Wasatch Plateau at an altitude of about 10,000 feet. These streams have a rapid fall in their upper courses, and leave the plateau through almost impassable cañons cut in its eastern wall overlooking Castle Valley. They flow across that at intervals of a few miles apart, and, then uniting, cut a deep, narrow cañon through the San Rafael Swell. Emerging from the swell, the river flows across a low, broken country until its junction with the Green. The largest body of arable land within the drainage basin of the San Rafael is in Castle Valley, a long, narrow depression lying between the eastern escarpment of the Wasatch Plateau and the San Rafael Swell. It is nearly 60 miles in length from north to south, and has an average elevation of 6,000 feet above the sea. Its southern end, as has been before mentioned, is drained by the tributaries of Curtis Creek, the central portion by the three streams forming the San Rafael, and the northern by Price River. No permanent settlements have been made in the valley, but it is much used as a winter herding ground for stock owned by the settlers in other portions of Utah. Lying near the branches of the San Rafael that cross it, and in such position that the water can be easily conducted over it, are 200 square miles of arable land, generally of good quality. East of the San Rafael Swell, and lying on both sides of the river, at an altitude of 4,000 feet, are 20 square miles of arable land, which could be easily irrigated. The river was carefully measured in July, 1876, and the volume of flow found to be 1,676 cubic feet per second. The three branches in Castle Valley were also measured, with results closely approximating the measurement of the united streams. These measurements were made at high water, though not when the streams were at their flood. As most of this volume is derived from the melting snow, which rarely disappears from the high plateau before the middle of July, the flow would be maintained with considerable steadiness during a large part of what would be the critical period in the irrigation of this valley. After the middle of July the decrease would be very rapid until September, and the lowest stage of water reached about the first of October, when the river would not flow probably more than 400 cubic feet.
THE PRICE RIVER.
This river rises in the angle formed by the intersection of the Wasatch and Western Tavaputs Plateaus, receiving tributaries from both these table lands, and has a general easterly course for 100 miles. It crosses the northern end of Castle Valley, and then flows through a broken country near the foot of the escarpment called the Book Cliffs, forming the southern boundary of the Tavaputs Plateau, till within 20 miles of the Green River, when it cuts through this escarpment into the plateau and joins the Green a few miles above the foot of Gray Cañon. The arable lands along its course are mostly found in Castle Valley, where there are at least 50 square miles—a quantity considerably in excess of the irrigating capacity of the stream. The volume of water was measured in July, 1877, a few miles below where it debouches into Castle Valley, and found to be 189 cubic feet per second. It must suffer great loss from absorption, as the volume when leaving the cliffs is much greater, and the aggregated flow of the branches on the plateaus is at least twice as great.