Modelagem da erosão hídrica na bacia hidrográfica do Rio Pandeiros em cenários de mudanças climáticas futuras

Abstract

The study of water erosion and intervening factors makes it possible to identify priority areas for preservation, aiming to reduce of the sediments yield. The Pandeiros River is a tributary of the São Francisco River, in the north of Minas Gerais, in a transition region between the cerrado and caatinga biomes. In its lower course, there is a wetland that has a recognized function of reproducing the ichthyofauna of the stretch of the São Francisco River between the Três Marias and Sobradinho reservoirs. Given the presence of degraded areas in the BHRP, such as gully and eroded roads, a growing concern is about sediment yield and siltation of the wetlands. In this context, the objective of this study was to map the susceptibility to water erosion in the Pandeiros River Basin (BHRP) based on the qualitative evaluation of the results obtained by the Revised Universal Soil Loss Equation – RUSLE. Specifically, the objective was to evaluate the possible impacts of future climate change on susceptibility to water erosion, based on the RCPs (Representative Concentration Pathways) 4.5 and 8.5 of IPCC-AR5. The statistical model for estimating erosivity (R factor) presented an adjusted coefficient of determination of 0.564, with precipitation as explanatory variable. For the current situation, the following values were obtained for the RUSLE fators: erosivity between 6,547 and 7,116 MJ mm ha-1 h -1 year-1 ,

erodibility (K factor) between 0.0067 and 0.0295 Mg h MJ-1 mm-1

, LS factor between 0.01 and 62.5, and C factor between 0.0004 and 0.29. The mapping of the susceptibility to water erosion identified areas with the greatest propensity, mainly in the northwest, central-north, east and southeast portions of the basin. The future climate changes scenarios projected reducing in annual precipitation of the 21st century, resulting in negative anomalies for the R factor and consequent attenuation of susceptibility to water erosion. However, it is understood that the concerns associated with the preservation of areas most susceptible to water erosion and the recovery of degraded areas remain unchanged, as the factors related to relief (LS factor), soils (K factor) and land use (factor C) were decisive in places most susceptible to water erosion. Caution is recommended when using the results associated with future climate change scenarios due to the various sources of uncertainty, and is suggested the development of new research addressing the scenarios of the Sixth Assessment Report of the IPCC-AR6; the study of the R factor in future climate change scenarios on the temporal scale of precipitation events; the study of C factor based on a detailed land use map, and the assessment of its temporal behavior throughout the 21st century.