How much selection and calibration of hydrological models influence climate change impact and adaptation conclusions?

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There is a large consensus in the scientific community that one must already envisage adaptation to climate change. In hydrology, the assessment of the impacts of changing climate demands the combined usage of three elements. First, climate projections are generated for long simulation time periods by global circulation models (GCMs), coupled to ocean and sea ice models, on a domain that covers the globe. Then a downscaling technique reconciles the scale mismatch between the large-scale climatic models and the watershed scale the most important scale for water management. Finally, a hydrological model simulates future watershed outflows. If lots of efforts have already targeted reducing the uncertainty of the first two components of such systems, little quantitative knowledge is as yet available about the role of hydrological model complexity. This study thus aims filling part of that gap by seeking an answer to the following: How much the selection and calibration of hydrological models influence climate change impact and adaptation conclusions? In particular, the project will implement twenty-two hydrological models on four river systems to evaluate the influence of the selection of a potential evapotranspiration formulation and the importance of pertinent hydrologic model parameter identification. Improper parameter selection may lead to a model that does not behave as the natural system it is seeking to simulate, while climate change may push potential evapotranspiration formulations beyond their calibration range. Four future climate projections will be used in the proposed study, the objective being to cover a wide range of plausible future temperatures and precipitations. The evaluation and comparison process will not only be based on typical hydrological scores and water balance components, it will also make use of real dam management applications as a complementary evaluation mean. Moreover, large differences in simulation will be analysed by looking in detail at the model structures. All this work aims improving Canada's ability for a timely adaptation of its water management schemes.