CHAPTER 4 – ESTABLISHING A RELATIONSHIP BETWEEN ...

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85Comparing Sediment Loads for Turbidity-Derived Predictions to TraditionalMethodsUSGS predicts stream constituent loads by relating stream discharge to individualsample concentrations using Graphical Constituent Loading Analysis System (GCLAS)software (Blanchard and Miller 2004). To evaluate the reliability of turbidity-derivedloads compared to those calculated with the USGS method, loads were calculated usingthe sediment-turbidity relationship at the USGS Station site for the period of June 9-20,2004, which included five storm events. Figure 4.5 shows precipitation, discharge,turbidity, TSS sample concentrations, GCLAS predicted sediment concentrations, andturbidity-predicted sediment concentrations at the site during the study period. Table 4.1displays daily loads as calculated by the turbidity method and USGS.Table 4.1. Mean daily discharge and sediment loads predicted by turbidity and USGSGCLAS software for the USGS Station Site, 9 <strong>–</strong> 20 June, 2004.DateMean DailyDischarge (cfs)Turbidity-PredictedSuspended Solids Load,metric tonsUSGS GCLASSuspended Solids Load,metric tonsPercentDifference06/09/04 84.1 173.7 102.5 + 69%06/10/04 105.0 37.8 29.9 + 26%06/11/04 154.2 59.9 147.0 - 59%06/12/04 155.7 89.4 111.6 - 20%06/13/04 138.8 61.9 51.0 + 21%06/14/04 108.2 12.2 11.4 + 7%06/15/04 73.8 3.8 4.3 - 11%06/16/04 50.7 3.0 2.4 + 28%06/17/04 99.7 123.9 57.5 + 115%06/18/04 81.0 11.6 7.7 + 50%06/19/04 67.9 4.1 3.9 + 5%06/20/04 47.1 1.7 1.9 - 11%Totals: 583.0 531.0 +10%
86Discharge (cfs)240220200180160140120100806040200ADischargePredicted TSSTurbidityTSS25002000150010005000TSS (mg/L), Turbidity (NTU)Discharge (cfs)240220200180160140120100806040200BDischargeActual TSS ConcentrationEstimated TSS ConcentrationGCLAS Estimated Concentration25002000150010005000TSS (mg/L), Turbidity (NTU)Hourly Precip. (mm)1614121086420C1009080706050403020100Cumulative Precip. (mm)Cumulative Precip. (mm)6/8/04 0:006/9/04 0:006/10/04 0:006/11/04 0:006/12/04 0:006/13/04 0:006/14/04 0:006/15/04 0:006/16/04 0:006/17/04 0:006/18/04 0:006/19/04 0:006/20/04 0:00Date - TimeFigure 4.5. Comparison of turbidity-predicted and GCLAS estimated sedimentconcentrations for the USGS Station Site, 8 <strong>–</strong> 20 June, 2004: (a) discharge,sediment samples, turbidity-predicted continuous sediment concentrations,and turbidity data, (b) discharge, sediment samples, and GCLAS estimatedcontinuous sediment concentrations, and (c) hourly and cumulativeprecipitation data.
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Page 3 and 4: 78absolute value, but a relative va
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Page 9: 84Determining the Effect of Streamf
Page 13 and 14: 88analysis showed a strong relation

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