Morphometric analysis of sub-basins Fojo and Perdizes in the city of Campos do Jordão, SP, Brazil

Abstract

The State of São Paulo Water Resources Policy established, in 1991, the Integrated Water Resources Management System (SIGRHI) and defined the basic principles for water management, adopting the watershed as the basic unit for studies, integrated planning for sustainable development. This study characterized the morphology of sub-basins Fojo and Perdizes in the city of Campos do Jordão, SP. Morphometric analysis involved the characterization of geometric parameters, topography and drainage network, and the analysis of land use and land cover of the sub-basins. The morphometric characterization revealed that Perdizes sub-basin has an area of 12.70 km², a perimeter of 19.85 km, and a main channel length of 6.86 km, while Fojo sub-basin has a drainage area of 13.97 km ², a perimeter of 19.74 km, and a main channel length of 6.94 km. These results indicate similarities between the two sub-basins. The compactness coefficient (Kc) for Perdizes was 1.56 and for Fojo 1.41. These values associated with the respective form factors, F = 0.27 and F = 0.29, indicate that these sub-basins, under a normal precipitation regime are not susceptible to flooding. The results of these indices are consisted with the circularity index (CI) found: CI = 0.41 for Perdizes and CI = 0.45 for Fojo, respectively. As CI values found are far from one, they indicate that these sub-basins tend to have a more elongated shape and, therefore, lower flow concentration tendency. The results obtained for the maintenance coefficient indicate that in order to maintain the flow of each channel meter, Perdizes sub-basin needs 286.5 m² and Fojo sub-basin needs 243.9 m². Land cover and land use analysis revealed that among the four existing vegetation cover types, Forest is dominant in both sub-basins with 649 ha (51.1%) in Perdizes, and 608.8 ha (43.6%) in Fojo; Reforestation cover ranks second with similar areas in both sub-basins, Perdizes with 218 ha (17.2%) and Fojo with approximately 214 ha (15.3%). In terms of conservation, Fojo sub-basin can be considered better conserved with a smaller urban area, larger rangeland natural coverage area, and only slightly smaller forest coverage area than Perdizes.