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1 <br />General <br /> <br /> <br /> <br /> <br /> <br />River Gage Installation and Data Collection <br />Estimating discharge in the Canyonlands reach requires the development of stage- <br />discharge relationship or rating curve. The two components of the rating curve are a discharge <br />measurement and a corresponding survey of river stage. A staff gage was installed at cross <br />section ANB-14 in Bonita Bend on river left. It is located in a large eddy, between house-size <br />large boulders in the river across from Anderson Bottom. <br />On June 5, 1995, an automatic stage recorder or level logger (WaterLOG Model DH-21 <br />pressure transducer) was installed at Queen Anne Bottom, about 1.5 miles upstream of the staff <br />gage (Figure 1). This level logger was erected when the flow was approaching the peak <br />discharge. It was difficult to stabilize the PVC pipe against the bedrock outcrop at the <br />moderately high discharge and twelve days later the level logger pipe detached from the bedrock. <br />The level logger was successfully recovered, but the stage data collection was limited to the <br />period from June 5 to June 17. <br />On Apri15, 1996, the level logger was reinstalled (Photo 1). The pipe was bolted directly <br />to the bedrock outcrop in several locations both at the bottom and top of the pipe. The soft <br />bedrock was unable to withstand the vibration of the pipe and mounting bolts and several of the <br />bolts loosened allowing the PVC pipe to shift up and down several times during high flow. The <br />level logger was removed on July 24, 1996. <br />' The level logger and staff gage were initially surveyed with respect to benchmarks <br />established during the FLO Engineering flooded bottomlands field work. The benchmark <br />elevation established on the canyon rim was approximate to the nearest foot. Re-installation of <br />the level logger required a survey of a reference water surface elevation to a local benchmark <br />near the level logger. The staff gage, barring disturbance, can be read in perpetuity to determine <br />discharge. <br />1 <br /> <br />i~ <br /> <br /> <br />Discharge Measurements <br />To calibrate astage-discharge relationship for the staff gage and level logger, discharge <br />measurements were required near the gage site. Standard discharge measurement equipment and <br />techniques were utilized in performing the discharge measurements which were collected from a <br />boat. In 1995, the discharge measurements were made in conjunction with the flooded <br />bottomlands project. All the 1995 and 1996 discharge measurements were used in the <br />development of a rating curve at the level logger location. The rating curve did not show any <br />noticeable shifts over a wide range of discharges. The channel morphology at the level logger is <br />relatively stable due to the bedrock outcrops in this reach. A summary of the discharge <br />measurements are presented in Table 2. <br />9 <br /> <br />