Scilab Function
Last update : 10/5/2006
c_GR2M - Function permitting to simulate runoff series from rainfall and evapotranspiration with GR2M model (monthly water balance)
Calling Sequence
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[Qcalc,[S,R,ECH,PR]] = c_GR2M(TimeSteps,Param,RAINFALL,EVAPOT,INI)
Parameters
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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.
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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].
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RAINFALL
: Rainfall expressed in mm (matrix [Nx1] where N is the number of time steps)
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EVAPOT
: Evapotranspiration expressed in mm (matrix [Nx1] where N is the number of time steps)
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INI
: Initial filling of soil moisture accounting and routing store reservoir (matrix [2x1] with values ranging from 0 to 1)
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Qcalc
: Catchment outlet discharge expressed in mm (matrix [Nx1] where N is the number of time steps)
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S
: Soil moisture accounting reservoir content expressed in mm (matrix [Nx1] where N is the number of time steps)
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R
: Routing store reservoir content expressed in mm (matrix [Nx1] where N is the number of time steps)
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ECH
: Water exchanges (matrix [Nx1] where N is the number of time steps)
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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
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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.
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WARNING : This function is written in C language and interfaced with SCILAB (HYDROGR.dll).
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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.
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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.
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To calibrate GR2M, the usual procedure is to use a "Pas à Pas" routine (cf function PasaPas).
Examples
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];
X =[665;1.18];
[Qsim,Ssim,Rsim]=c_GR2M(720,X,P,ETP,[0.6;0.7]);
subplot(3,1,1),plot2d(1:20,Qsim,style=2); // Calculated discharge
plot2d2(1:20,10-P,style=4); // Rainfall
subplot(3,1,2),plot2d(1:20,Ssim)
subplot(3,1,3),plot2d(1:20,Rsim)
See Also
PasaPas
,
Authors
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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: 113121.