Modelagem de práticas conservacionistas do solo em uma bacia hidrográfica no semiárido vulnerável a desertificação

Abstract

Water erosion is a natural phenomenon that can separate the soil into smaller particles, being transported by surface runoff until deposition in more flattened areas. Soil use and management based on conservation practices reduce the effects of water erosion and can be evaluated using hydro sedimentological modeling. Studies in this area are essential to analyze the impacts of land change and use and/or desertification, which is expanding significantly in the Brazilian semi-arid region. In this sense, the objective of this work was to evaluate the effects of two simulated conservation practices: terracing and dams, in containing erosion and sediment production in the Seridó River basin. The tool used in this analysis was hydrosedimentological modeling, where three numerical experiments were carried out: (1) control (CNTRL), where natural soil cover and long-term desertification were represented; and scenarios of soil conservation practices: (2) terracing (TERR) and (3) dams (BARR). The results found depended on the characteristics of exposed soil cover, the length of the river section, and the slope and were compared with the sediment production of the control scenario (CNTRL) for an average of 34 years at 3.24 ton.ha-1. year for the entire basin and with the area considered desertified (exposed soil) with an average of 17.26 tons.ha-1.year. The simulated conservation practices presented different results, where for the entire basin area the dams (BARR) had 47% retention efficiency, producing only an average of 1.72 tons.ha-1.year of sediment. However, at the sub-basin level in areas with a greater presence of exposed soil and slope, terracing had a better sediment retention efficiency with 57% producing an average of 7.45 tons.ha-1.year. Terracing and dams considerably reduced soil loss in river basins undergoing a desertification process, differences in the results of the practices are related to the slope.Conservation practices present effective reductions in sediment production in modeling, the development of these practices can help guarantee food security and water quality in the Brazilian semi-arid region.