Laserfiche WebLink
<br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />0763 <br /> <br />and constructing a sediment-discharge hYdrograph on a daily basis. <br />. <br /> <br />Flood flows were subdivided to obtain the sediment content on an hourly <br /> <br />basis. The annual volumes as computed are shown in table 15. The dry <br /> <br />weight of sediment was assumed at 75.7 pounds per cubic foot in order <br /> <br />to convert tons to acre-feet. The ten years of available sediment <br /> <br />records indicate an average annual rate of 812 acre-feet of suspended <br /> <br />sediment passing Trinidad, Colorado. Since the flood of 1942 occurred <br /> <br />during this ps',::'ci and produced two-thirds of the total sediment for the <br /> <br />period, and si.1<:e the frequency of this flood is computed at approxi- <br /> <br />mately once in 18 years, this average is high. The sediment-discharge <br /> <br />relationship curves based on the period of sampl;ng were applied to the <br /> <br />period of recorded flow on a daily basis from 1934 to 1939, and the <br /> <br />average volume of suspended sediment for the entire period, 1934 to 1949, <br /> <br />was computed at 561 acre-feet per year. Comparing the average flow <br /> <br /> <br />over this period with the average flow over the period 1921 through <br /> <br />1933, it is found the averages an aj(<:L. the same. Thus it is concluded <br /> <br />that the suspended sediment rate of 561 acre-feet per year is reasonable <br /> <br />for 29 years and will probably hold for a 75 year record. This amounts <br /> <br />to a suspended sediment production rate of 0.706 acre-feet per square <br /> <br />mile per year from the drainage a,."a above Trinidad, Colorado. <br /> <br />47. Experience with the suspended sediment computations for the <br /> <br />Arkansas River indicates that the open-mouth bottle method of sam- <br /> <br />p]jng tends to give an index of nearly the total load rather than <br /> <br />just the suspended sediment load. ~'Thether this holds true for the <br /> <br />Trinidad station on the Purgatoire River is not known,. but it is <br /> <br />believed that the suspended sediment computations may indicate <br /> <br />slightly more than the true suspended load. Also, it is believed <br /> <br />that the lower elevation areas have a larger sediment production rate <br /> <br />than those areas further upstream which are more mountainous. It is also <br /> <br />36 <br /> <br />APPENDIX B <br /> <br />~l j <br /> <br />. <br />