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A comparative study of the simulation of daily streamflow sequences Thambirajah, Percy Anandarajah

Abstract

Using three years of daily streamflow and meteorological data from the Similkameen watershed at Princeton, B.C., the model parameters of the existing deterministic UBC Budget Model are evaluated. With these model parameters and the available meteorological data, the synthetic streamflow sequences are generated for the other seven years for the Similkameen watershed. These are subsequently compared with the actual flows. A separate statistical stochastic model is developed by using the spectral analysis, and the three years of the same daily flows are decomposed into 30 sub-harmonics or Fourier coefficients. By interpolating the Fourier coefficients and by estimating the anticipated mean annual flows from the snowpack data at Blackwall Peak, the synthetic traces of the daily streamflow sequences are simulated for the other seven years. A first order Markovian model is used to explain the random component. The comparative study is then carried out between the actual daily streamflow sequences and those generated by the deterministic UBC Budget Model and the stochastic spectral model. In comparison with the stochastic spectral model, good fits are obtained with the fixed model parameters of the UBC Budget Model for the sequence of peaks for the simulated hydro-graphs of the intervening years. Since the winter melt factor in the UBC Budget Model was assumed to be a constant for this analysis, some errors occur between the actual and the generated cumulative volumes. With the deterministic periodic component of the spectral model, the reconciliation between the cumulative volumes is fairly well maintained. Since the role of operational hydrology is not concerned with the prediction of actual flows, the stochastic spectral model should be judged on its ability in presenting the designer with a series of synthetic traces that are likely to occur during the lifetime of a particular project.

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