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Performance of the ALS/ADCP, UALS/ADCP, and TS/ADCP models was determined with the RMSE and sum of squared errors (SSE) statistics (Table 2). The statistics were calculated from the observed discharges and the lower, upper, and entire portions of the rating curves. The lower and upper rating curve sections were defined about the discharge during the ADCP survey (i.e., 9.23 m3/s) which divides the ratings into ADCP-dominated and ALS-dominated spatial domains. It is clear that all three modeled rating curves have significantly lower errors than the empirical rating for all portions of the ratings. When comparing between the ALS/ADCP and TS/ADCP models, the ALS/ADCP shows slightly higher errors for all portions of the rating curve. Looking at the UALS/ADCP, the errors of the lower rating curve section are similar to those of the ALS/ADCP; however, the upper section and entire portion of the ratings show much higher errors than the TS/ADCP and ALS/ADCP models.

Table 2

Comparison of the sum of squared error (SSE) and RMSE determined from observed discharge, the lower half, upper half, and entire portion of the empirical and modeled rating curves

   Lower rating (<Qthresh)
  Upper rating (>Qthresh)
  Entire rating
StatisticQthresh (m3/s)NEmpirical rating (m3/s)TS/ADCP model (m3/s)ALS/ADCP model (m3/s)UALS/ADCP model (m3/s)NEmpirical rating (m3/s)TS/ADCP model (m3/s)ALS/ADCP model (m3/s)UALS/ADCP model (m3/s)NEmpirical rating (m3/s)TS/ADCP model (m3/s)ALS/ADCP model (m3/s)UALS/ADCP model (m3/s)
SSE 9.23 18 12.85 2.48 2.56 2.55 20 35.32 19.36 20.90 24.01 36 48.18 21.83 23.46 26.28 
RMSE 9.23 18 0.85 0.37 0.38 0.37 20 1.33 0.98 1.02 1.10 36 1.12 0.78 0.79 0.83 
   Lower rating (<Qthresh)
  Upper rating (>Qthresh)
  Entire rating
StatisticQthresh (m3/s)NEmpirical rating (m3/s)TS/ADCP model (m3/s)ALS/ADCP model (m3/s)UALS/ADCP model (m3/s)NEmpirical rating (m3/s)TS/ADCP model (m3/s)ALS/ADCP model (m3/s)UALS/ADCP model (m3/s)NEmpirical rating (m3/s)TS/ADCP model (m3/s)ALS/ADCP model (m3/s)UALS/ADCP model (m3/s)
SSE 9.23 18 12.85 2.48 2.56 2.55 20 35.32 19.36 20.90 24.01 36 48.18 21.83 23.46 26.28 
RMSE 9.23 18 0.85 0.37 0.38 0.37 20 1.33 0.98 1.02 1.10 36 1.12 0.78 0.79 0.83 

* Qthresh is the discharge used to define the lower and upper portions of the rating.

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