Eros?o h?drica em microbacia utilizando geotecnologias

• Autor(a) principal: Marques, Valter dos Santos
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFRRJ
• Texto Completo: https://tede.ufrrj.br/jspui/handle/jspui/3693
• topic: Perda de solo; Sedimentos; USLE; Soil loss; Sediments; Agronomia

To compare values of soil loss obtained by indirect and direct methods with the values of soil loss quantified in watershed outlets is necessary to assess the reliability of soil losses estimates. The objective of this research was to quantify the soil loss at the watershed outlet and to validate the methods of estimating soil loss by the USLE and with the rainfall simulator in the watershed of C?rrego ?gua Azul ? Ceres municipality, Goi?s State, Brazil. The study was conducted using the USLE, a rainfall simulator and monitoring the flux of water and sediments at the watershed outlet. The values of the erosivity factor (R) for the watershed were calculated using the different equations for twelve years and ranged from 586.7 to 9,583.3 MJ.mm.ha-1.h-1.year-1. For the circumstances of this research, the equation to calculate erosivity factor (K) that best approached the observed watershed data was the one proposed by Bouyoucos (HUDSON, 1982; BERTONI E LOMBARDI NETO, 1990) with K values varying from 0.006 to 0.014 Mg.ha.h.h-1.MJ-1.mm-1, and a weighted average of 0.014 Mg.ha.h.h-1.MJ-1.mm-1. The soil erodibility factor determined with the rainfall simulator varied from 0.0005 to 0.0039 Mg.ha.h.h-1.MJ-1.mm-1, and the weighted average was 0.0026 Mg.ha.h.h-1.MJ-1.mm-1. The annual soil loss estimated by USLE, in the different combinations of estimation methods of R and K, ranged from 0.023 to 7.71 t.ha-1. The soil loss varied from 0.22 to 1.72 t.ha-1.h-1, in the Oxisol and Ultisol classes, repectively, when using the rainfall simulator. The sediment loss observed at the watershed outlet was 166.6 t year-1 and the average sediment loss, estimated per hectare for a period of two years was of 0.619 t.ha-1.year- 1. The temporal parameters of this study from 2010 to 2012 demonstrated that, in some cases, the application of the USLE model without correction of the sedimentation rate generates soil losses very close to those observed at the watershed outlet, as in the C?rrego ?gua Azul. However, combinations of equations for rainfall erosivity and methods of soil erodibility that best estimated soil loss by USLE, when compared with the sediment loss in the watershed outlet varied greatly, depending on the study period (2010-2011, 2011-2012, and the average of 2010-2012), which did not allow a consistent choice of combinations for the site of study. The results demonstrated that the application of the USLE for soil loss estimates in watersheds is questionable, especially due to the complexity of obtaining values of erosivity and erodibility that are suitable for the study area. Moreover, the results lead to the conclusion that adjusting erosivity equations from conditions different than those from the study area may not be suitable, since the erosivity equations that yielded the best estimates were developed for places quite different from the study area. The monitoring of sediment loss in the watershed showed to be a viable and adequate way of estimating the watershed soil loss, mainly when this information is meant to be used for the payment of environmental services. It is highlighted that the watershed monitoring for longer periods will yield better soil and water loss estimates, as well as to improve the studies for the development of models to forecast watershed soil losses.