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<br />.' <br /> <br />r <br /> <br />. <br /> <br />STUDY OF FRICTION FACTORS IN THE UPPER REACHES OF THE <br />RIO GRANDE <br /> <br />Cassie C. Klumpp" Member ASCE and Drew C. Baird', Member ASCE <br /> <br />ABSTRACT <br /> <br />The ur of this study is to inve~tig8te ~he determination of Manning'fl <br />rou :oe:': the upper Rio Grande nver basin and compare re~ults to other <br />stu3ies where Darcy Weisbllch friction factors have been deter?Il~ed r~r S~Cf;;!I) <br />mountain streams. Three sites in the upper reaches of t~e RlO . ran e ~ve <br />adienls that exceed 0.002 mfm: the Rio Grande at El MedlO, Ihe Rio Gr~nde 01 <br />ft;e Vigil Ditch and the Rio Grande at El Guique. The El Med.o SIte ;~s <br />h elen:ents that are very large in relationship to the dept.h. c <br />~~~ ~:S8 ue Projects Office of the U.S. Bureau of Reclamation collected w.n":r <br />8urf8~e e~vations and discharge at these sites during the last 5 years. ~;~~Kt <br />coefficients were calibrated at each site using the com,puter program fi I . <br />Kl d B 'rd 1993) STARCAL produces multiple water surface pro 1 e!l <br />~or :~:c:nunti~lth~ RMS' error of the measured and simula~ wat~r surfa:e <br />. . . . d The selected roughness for the reach IS obtamed when <br />elevations are minImize . . , red t D cy <br />the RMS error is minimized. The computed MannIng s n was compo 0 ar <br />Wei~bach friction factors obtained by using dilTe~nt ~uations develo~edl f~~ l::~~ <br />and intermediate scale roughness for steep ~adlent tIVers. The eqUlva e . <br />grain roughness of the river was also exammed. <br /> <br />I Hydraulic Engineer, Sedimentation Section, Surface Water Branch, <br />U.S. Bureau of Reclamation, Denver, Colorado. <br /> <br />2 Chief, River Assessment Branch, Albuquerque ~rojects Office, <br />U.S. Bureau of Reclamation, Albuquerque, New MCX1CO. <br /> <br />102 <br /> <br />. <br /> <br />FRlCfION FACTORS-RIO GRANDE <br /> <br />70J <br /> <br />INTRODUCTION <br /> <br />The purpose of this study is describe the application of program STAH.CAL <br />to three steeper grndients portion~ of the upper Rio Grande. The computer <br />program has been used successfully to calibrate several sections of the river <br />characterized by fine to coarse grain material and smaller gradients. The program <br />works by using a linear regression technique to minimize the RMS error lwtwecn <br />measured and simulated water surface elevations in a 1 dimensional water RIlrfuce <br />profile program by varying the Ml1nning's n. The n is obtained when the error i!'l <br />at n minimum. The results oUhis effort will be compared to techniques developed <br />b.v I Bathurst, 1978; Thorne and Zevenbergen, 1985; Aguirre-Pe and I,'uentes, 19901 <br />for developing Manning's n or the Darcy Weishach friction factor in mountain <br />rivers. <br /> <br />The Rio Grande is a rime and pool type of stream with low sinuosity in the <br />upper reaches of the river. Three sites in the upper reaches of the Rio Grande <br />have gradients that exceed 0,002 mlm: the Rio Grande at "~I Medio, the Rio <br />Grande at the Vigil Ditch, and the Rio Grande at EI Guique. The EI Medio Site <br />is characterized by cobbles and boulders ranging in size from 127 mm. to 610 mm. <br />The 0,. oflhe material at El Medio is 203 mm. The 0.. ofthe bed material al EI <br />Guique is 30mm, and the I>fW of the bed material is 60 mm. The bimodal material <br />at the Vigil Ditch consists of sand sizes with a Dr;o of 0.5 mm to cobbles ranging in <br />size from 10 to 200 mm with a DMl of65 mm. Gradients oCthe Rio Grande at these <br />sites range from 0.OO2m1m to .005 m1m. <br /> <br />STUDY RESULTS <br /> <br />The model was applied at the three locations in the Rio Grande River Basin <br />8S shown on Figure 1. The calibrated Manning's n for the Rio Grande at El Medio <br />was 0.05 for a discharge of 12 cu mls obtained in September 1993. The water <br />surface profiles used to calibrate the reach are shown in Figure 2. The calibrated <br />Manning's n obtained for theVigil Ditch reach was 0.028 for a flow of 184 cu mls <br />for data collected in May 1993. The measured and simulated water surface profiles <br />for this reach are shown in Figure 3. The upper portion of the reach from station <br />o to station 1200 m is much steeper and the channel bottom is primarily cobbles. <br />When this section of the reach was caibrated separately, the Manning's n for the <br />reach was the same. These results compare favorably to previous calibrations <br />performed in May 1991, August 1991 and December 1993. The calibrated n for the <br />Vigil reach varied from 0.024 to 0.03 (Fullerton, 1992). The calibrated n for the <br />Rio Grande at EI GuiqlJ(~ was 0.05 for a flow of 9 eu. m1s obtained in September <br />1992. The measured and simulated water profiles used for the calibration at EI <br />Guique are shown in Figure 4. The RMS error between measured and computed <br />wB~r surface profiles for all three sites varied between .1 and .3 ffi. <br /> <br />Bathurst (1978) produced an equation to predict the friction factor for rivers <br />with large scale roughnC&SCs. For the EI Medio site the predicted Darcy-Weisbach <br />friction factor (0 using Bathurst's equation was 0.26. The f obtained by converting <br />the Manning's n of 0.05 from the STARCAL program was 0.20. This equation <br />applies over a range of relative roughness of RlD84 (R=hydrauHc radius) greater <br /> <br />- <br />