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1 ' General Level L~ger Installation and Data Collection The level logger (WaterLOG Model DH-21) measures water surface level with a pressure transducer at preset time intervals of typically either 1 ~ minutes, 30 minutes or 1 hour. These pressures (ft) are recorded on a computer chip inside the instntment plastic casing. The installation requires the erection of a 3 inch diameter PVC pipe mounted to bedrock along the river channel bank (Photo 1). The bottom four to six feet of the pipe have drilled 1/8 inch holes in four directions spaced about 6 inches apart to allow water into the pipe. The pressure transducer is set in the pipe below the lowest water surface elevation that will be monitored. The computer chip and casing is hung from the top of the pipe above the highest expected water surface elevation. A 12 ft to 15 ft PVC pipe is required to monitor the variation in the water surface elevation during the spring runoff season. The water surface elevation was surveyed when the level logger was installed. For this purpose, a survey bar and cap have been established at each site. Where local survey control and known elevation exists, the bar and cap was assigned an elevation. Additional water surface elevations were surveyed during discharge measurements. The water surface elevations were used to calibrate the stage-discharge relationships. Discharge Measurements ' A rating curve is required for each level logger to determine river discharge as a function of water surface elevation. Discharge measurements were collected at a nearby cross section which was established when the level logger was installed (Photo 2). Each discharge measurement was related to a surveyed water surface elevation at the time of the measurement. Four or five discharge measurements were used to establish the initial rating curve. Subsequent discharge measurements were used to determine the accuracy of the rating curve or any shift in the rating curve related to change in the cross section geometry or change in the channel bed elevation. Standard USGS procedures and equipment were used to collect the discharge measurement including a Price current meter, 20 or more discharge intervals, and Teledyne discharge instrumentation. A summary of the discharge measurements are presented in Table 1. ' Results ^ General The primary product of this investigation is a series of river discharge hydrographs prepared ' for each gaging site. The level logger estimated discharge results are plotted together with the USGS reported discharges at the Jensen and Green River gages. The discharge rating curves are presented for each level logger site.