Name

c_GR2M — Function to simulate runoff series from rainfall and evapotranspiration with GR2M model (monthly water balance)

Calling Sequence

[Qcalc,[S,R,ECH,PR]] = c_GR2M(TimeSteps,Param,RAINFALL,EVAPOT,INI)

Parameters

TimeSteps

Length of time series time step expressed in hour. Ex : for a montly model, TimeSteps = 720 (30 days).

The GR4J model has been optimised to run on daily values but the present function permits to utilise it with any time-step length.

Param

The four parameter values

Param(1) = Soil moisture accounting reservoir capacity (mm). Current values pertain to [400..600].

Param(2) = losses parameter (dimensionless). Current values pertain to [-2..2].

RAINFALL

Rainfall expressed in mm (matrix [Nx1] where N is the number of time steps)

EVAPOT

Evapotranspiration expressed in mm (matrix [Nx1] where N is the number of time steps)

INI

Initial filling of soil moisture accounting and routing store reservoir (matrix [2x1] with values ranging from 0 to 1)

Qcalc

Catchment outlet discharge expressed in mm (matrix [Nx1] where N is the number of time steps)

S

Soil moisture accounting reservoir content expressed in mm (matrix [Nx1] where N is the number of time steps)

R

Routing store reservoir content expressed in mm (matrix [Nx1] where N is the number of time steps)

ECH

Water exchanges (matrix [Nx1] where N is the number of time steps)

ECH

Effective rainfall, sum of the soil moisture accounting reservoir output and the direct runoff (matrix [Nx1] where N is the number of time steps)

Description

  • CAUTION : DURING THE FIRST YEAR OF SIMULATION (365*24 / TimeSteps), THE EFFECT OF THE INITIAL CONDITION (initial filling of soil moisture accounting and routing store reservoirs) IS NON NEGLIGEABLE. IT IS RECOMMENDED TO START EVALUATION OF MODEL RESULT AFTER ONE YEAR OF SIMULATION.

  • WARNING : This function is written in C language and interfaced with SCILAB (HYDROGR.dll).

  • The GR2M model (which stands for modele du Genie Rural mensuel a 2 parametres) is a monthly lumped two-parameter rainfall-runoff model. It belongs to the family of soil moisture accounting models.

  • Important features of the GR2M implementation in SCILAB :

    (1) The calculated discharges are expressed in mm ! To get values expressed in m3/s, one has to multiply this time-series by S/[3.6xTimeSteps] (S = Catchment surface in km2).

    (3) All values of rainfall or evopotranspiration inferior to 0 will be considered by the model as missing data.

    (4) 5 consecutive missing data are tolerated. The model affects 0 to the missing data.

    (5) With more than 5 consecutive missing data, the 2 internal variables (soil moisture accounting and routing store) are reinitialised.

  • To calibrate GR2M, the usual procedure is to use a "Pas à Pas" routine (cf function PasaPas).

Examples

      // Input data
      P   =[0.04;0.59;0.03;0.01;0.16;0.37;8.76;2.65;0.05;0.02;0.02;0.38;0.00;0.02;0.46;4.46;7.71;5.71;0.79;1.33];
      ETP =[0.24;0.24;0.24;0.24;0.24;0.25;0.25;0.26;0.27;0.28;0.32;0.33;0.34;0.35;0.36;0.36;0.37;0.37;0.38;0.38];
      
      // Parameters vectors
      X   =[300;1];
      
      // Simulation (time step = 240 hours = 1 month)
      [Qsim,Ssim,Rsim]=c_GR2M(240,X,P,ETP,[0.3;0.2]);
      
      // Plots
      subplot(3,1,1),plot(1:20,Qsim); // Calculated discharge
                    plot2d2(1:20,3-P/10); // Rainfall
                    xtitle('','Time','Discharge (mm/month)')
      subplot(3,1,2),plot(1:20,Ssim);xtitle('','Time','Production store level (mm)');
      subplot(3,1,3),plot(1:20,Rsim);xtitle('','Time','Routing store level (mm)');
  

See Also

GR_CAL_LM

Authors

Julien Lerat

CEMAGREF Antony, HBAN Unit, julien.lerat@cemagref.fr

Bibliography

Mouelhi, S., C. Michel, et al. (2006). "Stepwise development of a two-parameter monthly water balance model." Journal of Hydrology 318(1-4): 200-214

Perrin, C., C. Michel, et al. (2003). "Improvement of a parsimonious model for streamflow simulation." Journal of Hydrology 279(1-4): 275-289.

Edijatno and C. Michel (1989). "Un modèle pluie-débit journalier à trois paramètres." La Houille Blanche 2: 113–121.