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<br />1997, and plots were overlain to visually compare changes in bed geometry. <br /> <br />Calculating Effective Discharge From Sediment Records <br /> <br />.Effective discharge was determined by analyzing 847 suspended sediment <br /> <br />measurements made at the Watson gage. Sediment transport measurements were made <br /> <br />by the USGS between 1975 and 1990. A sediment rating relationship was developed by <br /> <br />fitting a best-fit power function to a plot of the 10gIo of daily suspended sediment in <br /> <br />kilograms/day vs. the 10glO of discharge in cubic meters per second. For the reach near <br /> <br />the Watson gage, this relationship was found to be: <br /> <br />Qsed = 931.63Q2.205 <br /> <br />where Qsed is sediment transport in kilograms/day, and Q is discharge in cubic meters per <br /> <br /> <br />second. Using the sediment rating relation, the amount of sedi~ent transported by given <br /> <br /> <br />increments of discharge was determined. A flow duration curve developed from <br /> <br /> <br />approximately 76 years of daily discharge values was then used to determine what <br /> <br />percentage of time a given discharge occurred during that period. The percentage of time <br /> <br />a given discharge occurred was multiplied by the sediment transported by that magnitude <br /> <br />of discharge, and the resulting product was plotted against discharge. The peak in this <br /> <br />curve represents the increment of discharge which transports the highest fraction of the <br /> <br />annual sediment load of the stream, the "effective discharge", as defined by Andrews <br /> <br />(1980). <br /> <br />Analysis of Discharge Records to Determine Threshold Discharges <br /> <br />We analyzed archived USGS discharge measurements for station 09306500 for <br />13 <br />