The UN World Water Assessment Programme - Scientific Paper - A Multi Model Experiment to Assess and Cope with Climate Change Impacts on the Châteauguay Watershed in Southern Québec

This paper discusses how participatory hydro-climatological modelling can be used to assess specific water issues on the Châteauguay watershed in southern Québec. It looks at different model responses regarding water budget dynamics, with a focus on summer water shortages and irrigation needs. It aims to stimulate water authorities’ and managers’ thoughts about climate-change adaptive planning options. The methodologies developed involve the use of a regional climate model providing climate information subsequently incorporated as forcing input (a) to two hydrological models (Hydrotel and Promet) and (b) to the FAO irrigation model. Results show that in climate-change scenarios for a 2050 time horizon, summer flows are projected to decrease while irrigation needs appear to increase considerably. The lesson learned from this modelling exercise reinforces the principle of forward-thinking, adaptive watershed-management strategies (regarding, in this case, water volume management for irrigation purposes). This exercise also shows that before proposing any adaptive solution, the issue needs to be assessed scientifically (in terms of water budget as well as in the socioeconomic domain) to evaluate the uncertainties of climate-change impact analysis, with respect to the multi-usage and integrated watershed management contexts of southern Québec. Climate change is in progress and affects many economic, social and ecological developments. In Southern Québec surface air temperature has increased during the period 1960–2005 and this warming is significantly evident in the western, southern and central parts of the province. In the summer, significant increasing temperature trends are found and precipitation indices indicate decreasing trends. Climate-change scenarios produced at Ouranos show that in the future, summer temperature will increase while no significant change is obtained for precipitation amount. This could lead to pronounced alterations in the seasonal water budget, putting increasing pressure on summer water availability and usage. Thus, reliable assessment of the potential climate-change impacts is necessary on a regional level. Suitable adaptation strategies must be developed in order to minimize adverse effects and to optimize possible benefits on water management issues. These adaptation schemes may profit largely from the careful integration of scientific model results into the decision processes of policy-making entities on different levels. This is not an easy task due to the manifold perspectives and interests in these issues. This paper discusses management issues arising from increasing agricultural water requirements under stressed water conditions, with the aim of optimizing possible benefits.

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