ANÁLISE ESPAÇO-TEMPORAL DA EROSÃO HÍDRICA EM BACIAS HIDROGRÁTICAS NO SUDOESTE DE GOIÁS

Abstract

Watersheds go through serious environmental impacts, such as soil erosion, which causes water resources contamination and pollution, thus interfering in the desirable water quality and availability for human use. Therefore, the objective was to perform a space-time analysis of the water erosion in Ribeirão das Abóboras (BHRA) and Ribeirão da Laje’s (BHRL) watersheds, located in the Midwest region of Brazil, and thus understanding the relation between use, coverage and loss of soil in BHRA for the years 1985, 1995, 2005 and 2015, and in BHRL for the years 1987, 1997, 2007 and 2017. For the present study, the Universal Soil Loss Equation (USLE) was used associated to geotechnologies (remote sensing, geoprocessing, GIS – Geographic Information System) to estimate the erosion rate of the watersheds soil. BHRA’s annual average erosivity was of 8,519.24 mm ha-1 h-1 year-1, and for BHRL it was of 8,046.96 mm ha-1 h-1 year-1, values that fit the two basins in the high erosivity class. The erodibility values varied from 0.018 to 0.023 t h MJ-1 mm-1 for BHRA, and from 0.017 to 0.044 t h MJ-1 mm-1 to BHRL. The potential erosion obtained varied from 0 to 3,230.11 tn ha-1year-1, with an average of 19.49 tn ha-1year-1 to BHRA. BHRL showed potential erosion varying between 0 and 5,055.11 tn ha-1year-1 and an average of 12.37 tn ha-1year-1. The land use and coverage factor had the highest values to exposed soil (1) and agriculture (0.30). Finally, the evaluated watersheds real erosion was obtained. The average soil losses to BHRA varied from 0 to 732.76 tn ha-1year-1, with averages of 1.6; 1.83; 2.68; and 3.40 tn ha-1year-1 for the years 1985, 1995, 2005 and 2015, respectively. The average soil losses to BHRL varied from 0 to 574.37 tn ha-1ano-1, with averages of 1.35; 1.76; 2.09; and 2.39 tn ha-1year-1 for the years 1987, 1997, 2007 and 2017, respectively. The BHRA space-time variation showed that the soil loss rate in 2017 is 112.5% higher than in 1987. For BHRL the increase was of 77.04% in 2015 compared to 1985. In both watersheds, the highest erosion values were associated with changes in land usage, such as the advancement of agriculture over the decades. At BHRA the average real erosion for agriculture increased 34.89% from 1985 to 2015. At BHRL this increase was smaller, corresponding to 4.83% from 1987 to 2017. This study demonstrates the importance of using models like USLE, which associated with geotechnologies is a great tool for environmental analysis.