run down a ravine for a distance of 2,800 feet, dropping 90 feet vertically in that distance. From this point the water will be diverted

FIG. 52.-Details of spillway gates at head of supply canal, Piney Creek to Lake De Smet.

by an earthen dam, 290 feet long on top, with a maximum height of 27 feet and slopes of 3 to 1 and 2 to 1 on the up and down stream

faces respectively, with a conduit similar to the one in the Little Piney dam, into a canal having a width of 14 feet on the bottom, a maximum depth of water of 12 feet, a fall of 1.056 feet to the mile, and a capacity of 960 second-feet, which may be safely increased to 1,000 second-feet if necessary.

The length of this section of the canal will be 4,500 feet, and it will bring the water to the northern rim of the lake basin (fig. 53). As it is desirable, for reasons given below, to place the outlet at the north end of the lake, the supply canal would have to be extended 4,000 feet farther so as to prevent the outlet from being filled with sediment, brought by water from the north slope of the basin. This additional 4,000 feet of canal would be in nearly level land, and would have a width of 32 feet on the bottom, a cut of 4.6 feet, and a maximum depth of water of 8 feet. In general, in all sections of the supply canal the side slopes will be 1 to 1 in cut, 14 to 1 on embankments, and 1 to 1 on cuts under embankments.

Clear Creek diversion.-Preliminary surveys were made of two possible conduit lines from Clear Creek to Lake De Smet (figs. 49 and 55), one of these leaving Clear Creek at Buffalo, the other 14 miles above Buffalo.

The one leaving the creek at Buffalo, where there is a good diversion site, is considered the more feasible. Four or 5 miles of this conduit would be along steep slopes, about 1 mile in deep cutting and about 1,500 feet in tunnel, all of which would be expensive. Owing to the absence of reliable data relative to the discharge of Clear Creek and the expensive construction of the conduit, it is not thought advisable to consider the project until after some measurements of the quantity of water flowing in Clear Creek, at the proposed point of diversion, are made. The area of the drainage basin of Clear Creek above the proposed conduit, including French and Rock creeks, is 284 square miles (fig. 49), just twice that of Piney Creek, above the proposed supply canal to Lake De Smet. The general elevation of the basin, however, is much lower, and for that reason it is doubtful if it discharges as much water as Piney Creek.

The biennial report of the State engineer of Wyoming, 1894, gives the following discharges:

Discharge measurements of tributaries of Clear, and Rock creeks in 1893.

The same report for 1895-96 gives the following appropriation of

water:

Clear Creek.....

Rock Creek..

Second-feet.

529

187

This would seem to indicate that there is not very much surplus water in these creeks.

The stored water may be taken out at the north end of the lake through a canal 9,700 feet in length, with a maximum cut of 30 feet,