3 solutions to non-stationarity problems Solution 1 – We need to keep constraining the AE by catchment water balance methods –Hydrological models Solution 2 - We need to constrain the AE by other ways –Fluxnet (but point data) –Satellite (just for the spatial pattern, or the temporal variability) –Biomass Solution 3 – We need more science –New formulations? Complementary hypothesis –Use extreme years or extreme climates

Evaporation Evaporation representation is maybe too few physically represented in our model ? Difference between latitude of the studied catchments Representation of interception? Is it crucial ? 2

Evaporation is (too often) a residual term… Correction of P  correction of ET, based on elevation Start to constrain the model with true data measurment! Scale issue Data from the FLUXNET (point measurment) 3

Divide catchments by « land class » and use satellite data as first guess? MODIS data for +/- estimation ? Water balance approach: streamflow and precipitation  R-R model Main problem in NS model: water balance 4

Difficulty to reproduce water balance over validation period High frequency term to take into account What about extreme years ? Regions without « formula », « data » (Russia, Alaska) 5

Question of extreme climate ? Definition of PET? Dependence on scale ! Definitions difference between hydrologists and climatologists definitions… Equilibrium equation shoulb be the best theoritically 6

What about biomass changes? Use as a constraint, at a annual timestep? 7