Resumo:
Water resource engineering has been largely employing flow forecasting models to
support decision making in several areas. The Previvaz and Smap Diário models have
already been used by ONS to forecast average weekly flows for up to six operating weeks
in order to provide the necessary inputs for the optimization of the hydroenergetic
resource in the planning of the operation of the Brazilian electrical system. Aiming at
adding efforts to improve this forecast, this work proposed and analyzed the results of a
weekly version for the Smap model, which was generated based on the calculation
mechanism of the monthly version of Smap. In the case study, the weekly Smap was
calibrated for two sub-basins of the SIN: the Camargos HPP basin (Grande basin); and
the Santa Clara HPP basin (Iguaçu basin). A back test was carried out for both basins for
the period between September 2019 and September 2020, comparing the flow forecast of
the Previvaz, daily Smap and weekly Smap models with the flows observed in the same
period. As a result, the Previvaz model, in the first week foreseen, propagated the trend
of flows observed in the previous week and in the other weeks it tended to overestimate
the lowest flows and difficulties in capturing peak flows. Both versions of the Smap
model showed an adjustment when the rainfall used to calculate the flows was the
observed rain, however both showed a tendency to overestimate the peak flows when
using the rain predicted by the CFS V2. It is concluded that the weekly version of Smap
performed better than Previvaz in most scenarios, indicating that it can be a model used
for planning the operation. In addition, the weekly version of Smap also showed better
results in the fifth and sixth week of the forecast horizon, indicating that the weekly model
can be used to improve the result of longer forecast horizons.
