There are several versions of the annual GR model. A description of the last version set up by Mouelhi (2003) is given here. An example of application is presented by Mouelhi et al. (2006).
The GR1A model comprises a simple equation:


  • Qk is the simulated streamflow of year k
  • Pk is the observed precipitation of year k
  • Pk-1 is the observed precipitation of year k-1
  • Ek is the potential evapotranspiration of year k
  • X is the parameter of the model to optimize

To know more: check our publications.

Download the Excel version of GR1A (in French).
GR1A is available in the R-package airGR.