The great unknown

IPCC global warming forecasts indicates a raise in precipitations over North America's northeast, a raise of mean annual temperature and snowfall, but a diminution in the duration of snow cover. This pattern is already verifiable on the northern part of Quebec, but it is less clear in the Great-Lake-St-Lawrence watershed where most of the population of Quebec is concentrated. Recognizing that climate change impacts cannot be predicted on a deterministic pattern, it is necessary to take into account the adaptation capability of a population, or its capability to anticipate change and invest to prepare room for maneuvre, the new tendencies in the nature, abundance and repartition of precipitations and foremost the balance between evaporation and precipitation at a large watershed level constitute the greatest unknown of forecoming climate changes. This short paper will try to caracterize impacts and path for adaptation in Southern Quebec facing anticipated changes in the hydrological regime.