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<br /> <br />. ~ ,. ,~ <br />'0.:1'" <br /> <br />1993 Resurvey <br /> <br />Fieldwork for the 1993 survey began in the spring of 1993. The hydrographic survey was <br />completed in late April near reservoir elevation 4859.0. The preliminary field work, <br />performed by personnel from the Eastem Colorado Projects Office and the Pueblo Reservoir <br />Operations Office, consisted of locating and flagging the existing sediment range end <br />markers, relocating the destroyed ones, and surveying the range lines not accessible by boat. <br />The hydrographic survey was performed using Reclamation's small boat bathymetric survey <br />system. The small boat system consisted of a sonic depth recorder and a reflector prism <br />mounted on the boat. The distances from a known point, usually one of the range end <br />markers, to the small boat were determined as the boat proceeded along the range line b) <br />an EDM (electronic distance measuring) instrument set up on shore and aimed at thE <br />mounted reflector target. Range distances were communicated by radio from the shore to thE <br />bOl:\t at preselected intervals and marked on the sonar charts as the boat proceeded acrOSE <br />the reservoir. The boat was held on course as closely as possible by radio communicatior <br />from the EDM operator to the survey boat. This system was used to collect the underwateJ <br />data for range lines 1 through lOA, 20, 21, 30, 40, 41, 42, 50, and 60. The data for rangE <br />lines 11 through 16, 43, 51, 61, and 62 were collected by conventional land survey methods <br />Da.ta were not collected for range lines 17, 18, and 70 because their location was not affectec <br />by previous reservoir operations. <br /> <br />RESERVOIR AREA AND CAPACITY <br /> <br />Development of 1993 Contour Areas <br /> <br />FOr the purposes of the sedimentation analysis and to better represent storage changes, th <br />reservoir was subdivided into segments, using the range lines to delineate the limit of eacl <br />segmental boundary. The 1993 reservoir surface areas were computed by the widtJ <br />adjustment method described by Blanton (1982) and illustrated on figure 5. The methol <br />entails computing the new segmented contour area, AI' between ranges by applying aJ <br />adjustment factor to the original segmental contour area, Ao. The computed adjustmen <br />factor for each segment was the ratio of the new average width to the original average widt] <br />for the ranges, outlining the segment at the specified contour elevation. The input dat <br />included the original and 1993 range line data along with the segmented areas for th <br />affected contour elevations. A comparison of simultaneous plots of original and 1993 rang <br />profiles indicated the lateral distribution of sediment at the different measured contou <br />elevations. Where these plots indicate changes have occurred on the side slopes of th <br />reservoir, a decision was made to determine whether the change was caused by actuE <br />deposition, erosion, or survey inaccuracies. No area adjustment was made if the measure <br />change was judged to be caused by survey inaccuracy. The 1993 total reservoir surface are <br />at a given contour is the original total area minus the summation of all segmental aree <br />silted in at that elevation. The 1993 total area computation results are listed in column (: <br />oftable 2. <br /> <br />1993 Revised Storage Capa<lity <br /> <br />The storage-elevation relationships based on the 1993 underwater survey data wel <br />developed using Reclamation's area-capacity computer program ACAP85 (Reclamation, 1985 <br />The 1993 surface areas resulting from the width adjustment computations at 5-foot contol <br />intervals were used as the control parameters for computing reservoir capacity. The progra: <br /> <br />4 <br />