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~ September 21, 1921 ~ ~ September 24--29, 1921 September 25-26,1921 September 29, 1921 September 30,1921 October 1,1921 June 7, 1922 Dugway Gage was permanently installed and consisted of a vertical low-water section from Oft to 9.5 ft, inclined middle section from 8 ft to 21 ft, and a high-water section from 21 ft to 28 ft. Elevation of the peak of the June 1921 flood was found to be 26,5 ft on this new gage (fig, B2). First stage measurement made at 6:25 p,m, The datum of the Dugway Gage was 3,106.16 ft above the NGVDI929. New Number 4 Gage was permanently installed. This gage replaced the old temporary Number 4 Gage on the large rock in the channel and the inclined Number 3 Gage on the left banle This gage consisted of a vertical low-water section attached to the large rock in the channel near the left bank below the Upper Cableway, and five higher-elevation inclined sections on the left bank. Vertical section read from 3 ft to 15 ft, and inclined sections read from 12.5 ft to 33.5 ft (fig. B3). Elevation of the road on the left bank was at a stage of 27 ft. Photographs indicate that, at the Number 4 Gage, this road was just above the elevation of the peak stage of the June 1921 flood, The datum of the Number 4 Gage was 3,106,82 ft above the NGVD 1929. Number 1 Gage was permanently installed and consisted of a velticallow-water section from 10,15 ft to 13.55 ft and an inclined higher-water section that extended from 13.5 ft to 23 ft. Low-water section was located about 117 ft downstream from the inclined section (fig. B4), Elevation of the peak of the June 1921 flood was found to be 30,89 ft on the Number I Gage. The datum of the Number I Gage was 3,102,60ft above the NGVDI929. Old temporary Number 4 Gage on rock was removed. The USGS computed daily mean discharge through this date from the stages measured at the Number 1 Gage. Because of uncertainties in how the stages measured on the LaRue Gage related to those measured on the Number 1 Gage, no daily mean discharges were published by the USGS prior to June 13, 1921. The USGS computed daily mean discharge after this date from the stages measured at the Dugway Gage. LG, Cockroft and Elmer Johnson measured the elevation of two high-water marks from the June 1921 flood at the Lonely Dell Ranch, The first of these marks was "about 8 inches above the ground on post offence near bottom wire" and was shown to Cockcroti and Elmer Johnson by JetTy Johnson, The con'ected NGVD 1929 elevation of this high-water mark was 3,132,64 ft, which equals 26.48 ft above the datum of the Dugway Gage. This high-water mark was only 0.02 ft lower than that measured on the left bank at the Dugway Gage. The second of these high-water marks was at the high-water edge of the alfalfa field near the fence and road, 1bis high-water mark was traced to be within 50 ft of the original gage on the Pmia River (this gage was one meander upstream. about 1,970 ft, from the CUlTent Pmia River gage). The high-water mmk consisted of small pieces of drift and grass, The corrected NGVD1929 elevation of this high-water mark was 3,132,61 ft, which equals 26.45 ft above the datum of the Dugway Gage. This mmk was only 0,05 ft lower than that measured at the Dugway Gage. These high-water marks were located between 0.6 and 1.2 miles diagonally downstream on the light bank of the Colorado River, and up the Pmia River valley. In a streamwise coordinate system, these mmks would be located about 0,3 miles downstream from the Dugway Gage, Therefore, the slope of the water surface in the reach immediately below the Dugway Gage was approximately 0,00001 to 0.00003 during the peak of the 1921 flood, Cl22H; Appendix B 71