Asa Sterling reservoir, from South Platte River; capacity, 75,533,000 cubic feet (1,734 acre-feet).

Jackson Lake reservoir, from South Platte River; capacity, 2,952,932,400 cubic feet (67,790 acre-feet).

Casis reservoir, from South Platte River; capacity, 396,000,000 cubic feet (9,091 acre-feet).

Lower Latham reservoir, from South Platte River; capacity, 270,700,000 cubic feet (6,214 acre-feet).

Cheesman Lake reservoir, from South Platte River; capacity, 4,000,000,000 cubic feet (91,827 acre-feet).

Sanborn Draw reservoir, from South Platte River; capacity, 3,060,525,600 cubic feet (70,260 acre-feet).

The superintendent of Irrigation Division No. 1 states that "in the districts in the South Platte division there are, in addition to the abovementioned reservoirs, 83 smaller ones, with capacities ranging from 60,000 to 100,000,000 cubic feet [1.4 to 2,300 acre-feet], which have been projected, and a great majority of them put into operation during the last two years." The aggregate amount claimed for these reservoirs would probably equal, if not exceed, that claimed for the firstnamed reservoirs.

There are already under construction two important reservoirs which lie along or near the proposed diversion line to Pawnee Pass.

Those reservoirs that are either already constructed or under way will draw the supply of water needed by them from the South Platte River in the immediate vicinity of the proposed diversion canal, and will require as much water as is shown to be available at the Kersey gaging station during the last two years. There would be required further for the filling of the Pawnee Pass reservoir an additional supply of not less than 2,500 second-feet for not less than five months, no part of which, so far as is shown by the records of the Kersey gaging station, can be obtained. When it is considered that canals below the mouth of the Cache la Poudre require for their use during the irrigation season at least 2,000 cubic feet per second, and that within the last two years there has been almost no time during the irrigation season when these ditches had any water except the seepage from the river, the gravity of the situation becomes at once apparent.

The projects already under way must have an ample supply of water for storage, and there are many thousands of acres under irrigating canals which can not be supplied even through the use of these new reservoirs. It has been argued, therefore, that it is inexpedient to endeavor to bring new lands under cultivation in this region. The figures appear to indicate that it is not desirable to attempt to fill the Pawnee Pass reservoir and irrigate additional arid lands until it is evident that there is an abundance of water for the present reservoirs and that the lands now under ditch have allotted to them a sufficient supply. Estimates of water supply of most importance in this connection are those of the flow of South Platte River at Kersey, this being the nearest point to the proposed works of the Sterling project.

Estimated monthly discharge of South Platte River at Kersey, Colo.

In Idaho irrigation has been developed mainly along Snake River and its tributaries in the southern or wider portion of the State. Toward the north the State lines converge and include a strip of high mountain area with narrow valleys, where the climate is semiarid, or even humid, the water supply large, and agriculture has developed rapidly without irrigation. In the south, however, the State extends across broad stretches of lava-covered plains upon which the rainfall is scanty, and the soil can not be successfully tilled without an artificial supply of moisture. In the northern or nonirrigated counties of the State over one-half of the acreage produces crops consisting largely of barley and wheat. In the southern portion the principal crops being raised under irrigation are alfalfa, hay, and grains cut green for forage, also orchard fruits, potatoes, and vegetables.

The total area irrigated in 1899 was a little more than 600,000 acres, being an increase of over 100 per cent in the preceding ten years. The

irrigated lands, as shown by the map (fig. 22), are mostly in the southern counties. The largest area is near the headwaters of Snake

H. Doc. 79-11

River, on the eastern side of the State, and is devoted mainly to forage crops. On the western side of the State the irrigated areas are smaller, but, the altitude being lower, the value of the crops per acre is larger. The following table shows the area of vacant public land on June 30, 1901. A summary of the conditions, by States, on June 30, 1902, taken from the report of the Commissioner of the General Land Office will be found on page 19.

Unappropriated, reserved, and appropriated areas in Idaho on June 30, 1901.

The opportunities for the reclamation of arid lands are confined mainly to the southern part of the State, since, as above stated, the valley lands of the northern end are relatively limited and humid. The broad lava-covered plains of the south are for the most part still owned by the General Government. Water has been taken out of the tributary streams wherever it could be diverted at moderate expense. The largest development of unutilized lands is that made possible by

the complete control and diversion of the waters of Snake River. The matter has been studied with great care by Mr. D. W. Ross, who, through his position as State engineer of Idaho, has given particular attention to various problems.

SNAKE RIVER DIVERSION.a

The following statements are taken from a preliminary report by Mr. Ross upon the conditions existing in Snake River Valley. He calls attention to the fact that the rapid development of the agricultural resources of the upper Snake River Valley during the last three years has aroused more than ordinary interest in projects for the reclamation of other large bodies of desert lands in that vicinity. Although this development may be said to have just begun, the diver sion of the entire flow of the river during the month of August, 1901, surprised the people of the district and showed how necessary it is that the public should be in possession of more facts in relation to the demands which are likely to be made upon this source of water supply before many years, and in regard to the storage facilities which exist for regulating the flow of Snake River, so that all the land. depending upon it may be reclaimed.

The lands classified as "irrigable" in this discussion are those lying below the level of canals already constructed or partly constructed, or below the line of proposed canals whose construction is known as feasible.

UPPER SNAKE RIVER VALLEY.

Of

What is known as the "Upper Snake River Valley" is the country lying between American Falls and the headwaters of the river. The irrigable portion of this valley is about 135 miles long, and averages nearly 9 miles in width, comprising, all told, about 700,000 acres. this tract about 215,000 acres are now irrigated; about 490,000 acres lie below the level of canals already constructed or partly constructed; about 121,000 acres are within the boundary of the Fort Hall Indian Reservation, while the remainder, 90,000 acres, lies below the level of a proposed canal system on the west side of the river near the lower end of the valley. There are 30,000 acres of irrigable lands on the upper tributaries, of which 15,000 acres are irrigated.

The fall of the river through the upper portion of the valley averages nearly 6 feet per mile. The high-line canals on the east side of the river follow the foothills, which rise rapidly into high mountains. The contour of the west side is comparatively level, great plains stretching out from 20 to 75 miles from the river, constituting what is commonly known as the "Great Snake River Plains."

a From report of D. W. Ross, State engineer of Idaho.