Application of an upscaled hydrological model to five Oklahoma watersheds of the CAMELS database.

An upscaling approach of 3D hydrological processes for Land surface models (LSM) has recently been developed and tested on the Little Washita experimental watershed (Ok., USA). We show here how the resulting upscaled model, which depends on two hydrologic variables, may be encapsulated into a vertical soil column model. This upscaling approach allows to establish the relationships between the physical and geometrical parameters of a watershed and the empirical parameters of the LSM ORCHIDEE. A comparison of both models on the Little Washita is discussed. Then, we test this new model on five watersheds located in Oklahoma (USA) and picked from the CAMELS database. All the geometrical and physical parameters come also from the database except the van Genuchten infiltration parameters obtained by a calibration algorithm. The five watersheds cover a wide range of areas and hydroclimatic conditions of the south great plain region. The results show that the monthly inter-annual means and annual means KGE values are comparable to those obtained with SACMA which is the reference model of CAMELS. As a conclusion, it is worth to emphasize that the quality of our results depends essentially on the calibration of the infiltration parameters. This work will be extended to other watersheds of the CAMELS database.