Development and application of a rainfall-runoff model for semi-arid regions

Despite the advances undertaken in recent years, modeling watershed's hydrological responses remains a complex task, especially in data-scarce areas. In order to overcome this, new models with distinct representations of hydrological processes continue to be developed, incorporating spatial data and geoprocessing tools. In this article, the CAWM IV (Campus Agreste Watershed Model Version IV) model is presented. It is a conceptual model developed with the purpose of contributing mainly to the hydrological modeling of basins inserted in semi-arid regions. The article provides the layout of the mathematical model structure and a set of results obtained from the application of the model to basins with different characteristics. The main features of the model are the reduced number of parameters to calibrate and the incorporation of the basin physical characteristics in the calculation of several attributes, in order to facilitate the process of regionalization for other similar basins, particularly due to the absence of flow data. The CAWM IV model was applied to four basins located in the state of Pernambuco, in the Northeast region of Brazil. The model presented adequate behavior for 55 to 92% of the simulated events, depending on the criteria of performance indicators used in the analysis.