MODFIPE - um modelo distribuído de base física para simulação do escoamento e erosão do solo.

Abstract

The runoff erosion modelling is related to the processes of the hydrologic cycle. To model satisfactorily these processes it is important to consider physical parameters of the systems such as the infiltration capacity, hydraulic conductivity, soil tension and the relationships between them and soil moisture content. The model MOFIPE was designed to calculate the runoff and erosion processes considering these characteristics. However, the climate variability, catchments heterogeneities, and the channel system and routing procedure were not taken into account. In this work the distributed model MODFIPE is proposed, which considers these heterogeneities, i.e., the space variability of the rainfall, soils, relief, evapotranspiration that can be calculated using different methodologies, and the routing procedure in two orthogonal directions, X and V. These aspects make the new approach suitable for being applied at heterogeneous systems. Runoff is generated either by rainfall excess over infiltration capacity, excess of soil moisture content over saturation or both. Soil erosion is determined by the squared moment of the rainfall, and runoff when the shear stress of the flow exceeds the resistance of the soil. Sediment transport depends on the transport capacity of the flow that can be calculated using alternative methods, one of which with the sediment size distributions of the eroded soil. In order to accomplish such features, a friendly and interactive interface has been designed in DELPHI®, with a reasonable graphic interface. Two simpler versions, one in FORTRAN g77® and another using the EXCEL® spreadsheet, have also been designed. The model workability was tested and validated through simulations realized for some catchments in the semi-arid region of Northeast Brazil, the Umburana sub-basin of the Representative basin of Sume, the micro-basins M3 and M4 of the Experimental basin of Sume, in the state of Paraiba, and the sub-basin of Mundo Novo of the Representative basin of Taua in the state of Ceara\