Modeling of the effect of land use changes on the runoff generation of a river basin through parameter regionalization of a watershed model

A conceptual rainfall-runoff model was applied to 95 catchments in the Rhine basin for the purpose of modeling of the effect of land use change on the runoff. An approach to calibrate the model by associating the model parameters with the physical catchment characteristics was implemented. Land use, soil type, catchment size, and topographic structure were used as the bases for regionalization of the model parameters. Parameter values were initially associated with these catchment characteristics and were finally transferred into their catchment scale values using a transfer function, whose form was assumed a priori. A simultaneous model calibration was performed for a number of catchments with contrasting catchment characteristics. An optimization algorithm was used for the calibration with an objective function defined as the normalized sum of the squared differences between the modeled and the observed runoff. The regionalized model thus obtained was then used to model the resulting runoff for different land use scenarios generated in the model area. The results obtained suggest that increased urbanization leads to an increase in the lower peak runoff resulting from summer storm, while the increase in the higher peaks resulting from winter rainfall is very little. On the other hand, a considerable reduction of both the peak runoff and the total runoff volume resulted from intensified afforestation.