In the currently financed phase of the project, the global climate change likely to take place according to the ‘2 x CO2’ scenario was assessed on the basis of outputs from two general atmospheric circulation models.

We then used the perturbation method to disaggregate the global meteorological indications obtained to the more detailed scales needed for hydrological modelling. The resulting climate forcings were intended for application to a number of hydrological modellings of the French part of the Rhône catchment and other tributaries of particular interest.

This preliminary phase of the project also included rewriting a detailed proposal to follow up the first project, with the idea of deducing from the hydrological modelling indications concerning the effects of climate change on the major physical variables of the studied hydrosystems and assessing impacts on various physical, biological and socio-economic aspects – in particular the general hydrology of rivers (high water, median discharge, low water), the interactions with groundwater, the expected trend of the water temperature, the quantitative and qualitative trends of the natural vegetation, the altered relationships between water resources and irrigated crop systems, and the response of the fish communities to alterations of the water regime.

Thoughout the project, the authors made a point of expressing and quantifying the uncertainties to be found in current studies (using a number of models for global trend scenarios as well as for hydrological modelling).

The preliminary phase is expected to provide a set of atmospheric and hydrological scenarios consultable as needed by hydrological model-designers involved in the project.