TITLE:
Calibration and Validation of the GR2M Hydrologic Model in the Kouilou-Niari Basin in Southwestern Congo-Brazzaville
AUTHORS:
Christian Ngoma Mvoundou, Christian Tathy, Harmel Obami-Ondon, Guy Blanchard Matété Moukoko, Richard Romain Niere
KEYWORDS:
Kouilou-Niari Catchment Area, Rainfall-Runoff Modeling, GR2M Model, Nash-Sutcliffe Criterion, Calibration Phase, Validation Phase
JOURNAL NAME:
Open Journal of Modern Hydrology,
Vol.12 No.3,
July
29,
2022
ABSTRACT: The hydrologic simulation of a catchment area,
described as the transformation of rainfall into runoff, generally uses
hydrologic model. This work opts for the global conceptual hydrologic model
GR2M, a monthly time step model, to study the Kouilou-Niari basin,
the second most important ones of the Republic of Congo. This includes two
parameters to model the hydrologic behavior of a catchment area. The choice of
the conceptual model GR2M is justified by the reduced number of parameters and
the monthly time scale. The
objective of this study is to determine the characteristic parameters of the
GR2M model, by a calibrating and a validating procedure. The use of these
parameters enables to follow the evolution of the water resources from the
climatic variables. It has been first carried out a characterization of some
physical, geological and climatic factors governing the flow, by dealing with
the main climatic variables which constitute the inputs of the hydrologic
model. Then, a hydrologic rainfall-runoff modeling allows to calibrate and
validate the model at monthly time scale. Taking into account the number of
parameters involved in hydrologic processes and the complexity of the cathment
area, this model gives acceptable results throughout the Kouilou-Niari basin.
The values of the Nash-Sutcliffe criterion and those of the correlation
coefficient obtained are greater than 80% in validation, which explains the
performance and robustness of the GR2M model on this basin.