ABSTRACT: Impact of statistical disaggregation of precipitation in physically-based distributed hydrological modeling. Case Study: June 2002 flood on the Des Anglais Watershed, Quebec, Canada.

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Abstract

Physically-based distributed hydrological models (PBDHM) can simulate streamflow at local scale. When an extreme precipitation event is imminent, meteorological forecasts may be used as input in a PBDHM to estimate the resulting peak flow. However, meteorological forecasts are generally available on mesoscale grids (102 – 103 km2), which might not be accurate enough to simulate local scale stream flows. Statistical disaggregation models can rapidly provide several series of high-resolution precipitation data while preserving the total amount of precipitation of the mesoscale grid. The aim of the present work is to evaluate the potential of using disaggregated precipitation series in a PBDHM to predict local stream flows within a watershed. As a case study, we analyze the June 2002 flood on the Des Anglais watershed (730 km2), located in the Saint Lawrence Lowlands, Quebec, Canada, using the PBDHM HYDROTEL. A recently developed Gibbs sampling disaggregation model is used to downscale a 52-km precipitation field onto a 4-km precipitation grid. Results from the watershed’s 182 relatively homogeneous hydrological units (RHHU) show that disaggregated precipitation series produce a large spectrum of runoff estimations, especially on the smaller units. The physical processes simulated by HYDROTEL leading to these different runoff estimations are analyzed to understand the impact of disaggregation and provide guidelines for its application in local flood forecasting.

Bibliography of Canadian Geomorphology