MEASUREMENTS OF PAWNEE CREEK, It has been urged that Pawnee Creek alone would furnish sufficient water for the proposed system. This, however, is not true. The drainage area of Pawnee Creek down to the site of the proposed dam is 682 square miles, the precipitation being on the average about 15 inches per annum. In the sandy drainage basin of Pawnee Creek it would be extraordinary if even one-sixth of the total precipitation were to become run-off, which would give only 72,750 acre-feet, about one-fourth the capacity of the proposed reservoir, while in many years the run-off would be practically nothing. But more than this, the greater part of the run-off of this stream occurs during the irrigating season, when those owning canals along South Platte River below the mouth of Pawnee Creek have a right to the water discharged from that stream, so that no part of the summer flow would be available. It has been reported that several times during the summer season of 1902, when there was an unusual number of violent storms, enough water was discharged by this stream to fill the proposed reservoir. The records of the Julesburg gaging station, at the lower end of irrigation district No. 64, show that there was but one rise of any importance during that season, and the reports of the commissioner of water district No. 64 show that this rise was caused by heavy rains on streams entering the South Platte below the mouth of Pawnee Creek and on the other side of the river. Under the laws of Colorado the proposed reservoir would not be permitted to hold back the discharge of Pawnee Creek until after the requirements of all irrigators below were satisfied, and by that time the flood would invariably have passed. Moreover, even if it were true that the flow from the violent storms or cloudbursts were sufficiently great to enable this discharge to be thus utilized, the amount of sediment that is carried in streams of this type during great discharge, due to cloud-bursts, would soon fill the entire reservoir with silt. These facts demonstrate beyond question that the water supply of South Platte River and its tributaries is inadequate to warrant the construction of the proposed system. There is an abundance of land of the finest quality, capable, with a good water supply, of raising good crops; but the water supply is entirely inadequate, and even if there was plenty of water the cost of getting the water to the land would be so great as to prohibit the construction. UNCOMPAHGRE VALLEY PROJECT. A preliminary report concerning the Uncompahgre Valley reclamation project was printed in the First Annual Report of the Reclamation Service, pages 132-149. 182 It l water Thi dam i 15 in it wo were one-f the I great seaso mout strea It of 19 wate The gatic tance distr ente the rese Cree and ever burs ized duri rese T Sou cons of t goo ther WOL A tion tion TOPOGRAPHIC MAPPING. During the month of December, 1902, an effort was made to keep up the topographic mapping of the Uncompahgre Valley, but the progress made was unsatisfactory, owing to extreme cold and frequent storms. This work was therefore discontinued in January, 1903, and the field parties were disbanded. The months of January, February, and the first week of March, 1903, were occupied in the compilation of the data already obtained and in making preliminary estimates. The preliminary report was completed on March 6, and further surveys were ordered, so that complete reports might be submitted as soon as practicable. A system of triangulation of the entire valley was planned in March, 1903, and the necessary base lines were established. Leveling also was commenced. This triangulation work and the primary level lines necessary for the topographic work were completed in May. On June 18 the topographic mapping was begun, under the general direction of Joseph A. Sargent, assistant engineer. On June 17 Ira W. McConnell, engineer, was placed in charge of the work as resident engineer, and since that time the surveys have been under his direct supervision. The topographic mapping has been carried on diligently throughout the remainder of the season, six parties having been at work during the greater part of the time. It is hoped that the entire valley will be thoroughly mapped by the time it is necessary to close this line of work for the winter. The platting is being done on a scale of 1,000 feet to the inch, showing 10-foot contours. Detailed topographic maps of each end of the proposed tunnel line have been made on a scale of 50 feet to the inch, with 5-foot contour intervals. At this date about two-thirds of the entire valley has been mapped. This work is done for the purpose of showing clearly the amount of irrigable and nonirrigable lands, and the general topography of the Uncompahgre Valley, so that the location of canals may be more readily made. The lands are being classified into irrigable and nonirrigable. lands, the irrigable lands being subdivided into first, second, and third grades. An interesting and at the same time extremely dangerous piece of topographic surveying was completed in August, 1903. It became necessary to make a topographic survey of about 1,500 feet of the bottom of the Grand Canyon of the Gunnison River, at the point selected as the location of the head of the proposed tunnel. The canyon here is approximately 2,000 feet in depth, the walls being almost sheer precipices. The water flows very swiftly over huge bowlders and through narrow gorges, and it is therefore impossible, particularly at high stages, to use boats or to traverse the canyon for any distance. To obtain the topography of this section, therefore, it was necessary to descend into the canyon over cliffs and through narrow fissures in four different places. The talus slope for about 600 feet on the south side of the river was mapped first, by descending through a narrow fissure. It is through this fissure that it will be necessary to construct a cableway for the purpose of carrying supplies and materials into the canyon after construction commences. The party, making a detour of approximately 150 miles, came down a similar fissure on the opposite side of the river, and mapped that side for a short distance. About 1,200 feet farther upstream they were able to descend again to another short talus slope, the descent being extremely perilous and accomplished at times only by the use of ropes over steep cliffs hundreds of feet in height. On the opposite side there was found another small talus slope, which was reached by a similar descent from the south side after the return of the party. One small tract between the extreme limits could not be reached with instruments, although one man descended to this point also, by means of ropes, in order that he might set signals for triangu lation. This dangerous piece of work was at last satisfactorily concluded. The men making the descent into the canyon were I. W. McConnell, resident engineer; W. P. Edwards, engineer; J. A. Sargent, topographer; and L. E. Foster, assistant topographer. The accompanying map (Pl. XXIII) shows the topography at this point, the physical features being more clearly shown by the accompanying photographs (Pl. XXIV). TRIANGULATION. A comprehensive system of triangulation covering the entire Uncompahgre Valley was carried out during the earlier part of the season. Triangulation points were established at distances varying from 1 mile to 5 miles apart, in order to have at least one triangulation point, and preferably two, represented on each plane-table sheet. The instrument work was done by W. P. Edwards, engineer, and Lavern J. Charles, assistant engineer, with No. 1 Berger transits, reading by estimate to 20 seconds of arc. The work was done with extreme care, and angles were found to close within 15 seconds on calculations of the latitudes and departures. The entire triangulation system was carried across Vernal Mesa also, most of the work being done by Mr. Edwards in May and June. The purpose of this triangulation was to check the work of the year 1902, and to determine further facts relative to the distances between Uncompahgre Valley and various points at corresponding levels upon Gunnison River. From Fairview siding triangulation was carried to Gunnison River at Boat Landing, connecting with Bostwick Park base, with the work |