SWAT PERFORMANCE AS INFLUENCED BY POTENTIAL EVAPOTRANSPIRATION FORMULATIONS IN A CANADIAN WATERSHED

Selecting a potential evapotranspiration formulation (PETF) for hydrological modeling is not a trivial task, so hydrologists often opt for a familiar formulation or one that is already available within the model they use. This article investigates the Soil and Water Assessment Tool (SWAT) sensitivity to PETF, in terms of performance and behavior, in a contrasted climate context, for a Canadian catchment subject to spring freshet. For this matter, twenty PETFs are tested in addition to the three available in SWAT. The analysis consists of a Sobol' parameter sensitivity analysis and a shuffled complex evolution (SCE) calibration over four climatically contrasted periods. Results show that PETF affects SWAT's performance, particularly in a dry climate, but also affects SWAT's behavior in terms of parameter sensitivity and optimal parameter sets. These results stress the importance of selecting a PETF appropriate to the modeling objectives.