Resumo Como consequência da interferência do uso e cobertura do solo no processo erosivo, conhecer a dinâmica de uma bacia hidrográfica que é utilizada como fonte de água destinada ao abastecimento urbano, é essencial. Devido à sua complexidade e a necessidade de fazer estimativas, o desenvolvimento de modelos matemáticos é fundamental para tomadas de decisão assertivas. Dentre os modelos existentes, o modelo (Soil & Water Assessment Tool) SWAT é um dos mais utilizados no mundo. Neste contexto, o objetivo do trabalho é comparar o uso do solo no manancial do Ribeirão do Feijão, localizado no sudeste do Brasil, entre períodos distintos e estimar a produção de sedimentos relacionando com o uso do solo da bacia, utilizando o SWAT +, assim como definir áreas prioritárias para melhoria do cenário de qualidade da água. A simulação foi realizada dividindo a bacia em sub-bacias e atribuição de múltiplas Unidade de Resposta Hidrológica (HRUs). As métricas utilizadas para analisar a eficiência do modelo indicam que os resultados satisfatórios, com Nash-Sutcliffe (NSE) de 0,53 e 0,54, para calibração e validação da vazão, respectivamente. O modelo representado nesse estudo pode contribuir para orientar futuros planejamentos do uso e cobertura do solo, viabilizando a previsão de distintos cenários e possíveis impactos na produção de água.

Abstract The change of natural landscapes by anthropic activities is the main reason for the erosion deepening. Thus, it is necessary to know the processes that determine the hydrological balance to avoid erosion in this context. Due to the complexity of a basin and the need of making predictions, the development of mathematical models is essential for decision making. Among the existing models, the Soil and Water Assessment Tool (SWAT) is one of the most utilized models worldwide. Thus, the present study aims to compare the land use between different periods and quantify the soil loss in a basin (Feijão River, in the Brazilian southeast), using the SWAT + model, as also to provide guidance to decision making by determining priority areas to improve water quality. The simulation was performed by dividing the basin into sub-basins and assigning multiple HRUs. The metrics used to analyze the model's efficiency indicate that the results were satisfactory, Nash-Sutcliffe (NSE) of 0.53 and 0.54 for calibration and validation of streamflow, respectively. The model represented in this study can help guide future planning for land use and occupation of the basin, enabling the forecast of different scenarios and their possible impacts on water production.

ABSTRACT Erosion process occurs naturally, shaping the Earth’s surface. Soil loss can cause harmful effects to the environment when intensive anthropic activities occur. Mathematical models have been used as effective and less costly alternatives for identifying sites highly prone to soil loss, especially at the watershed scale. In Brazil, the Revised Universal Soil Loss Equation (RUSLE) is one of the most commonly used soil loss prediction models. The RUSLE requires information on soil erodibility, rainfall erosivity, topography, land use and cover (C), and conservation practices (P) to estimate average annual soil losses. Images derived from remote sensing techniques are generally used to quantify the spatialization of C factor; however, the variation in land use throughout the year is not usually considered. This study aimed to estimate soil losses in an important subwatershed of Candiota river watershed (CRWsub) by using RUSLE, considering land use and rainfall erosivity in different periods of the year. The periods considered were P1 (January, February and March), P2 (April, May and June), P3 (July, August and September) and P4 (October, November and December). Based on the results, the lowest soil losses occurred in P1. Probably, the high vegetation cover in the soil increases its protection against rainfall erosivity. In P3, the heavy rainfall events are predominantly frontal, occurring in the same months as those when the preparation of the soil for later planting takes place; that is, there is no vegetation cover in this period, thus making the soil more prone to erosion. The use of different images to classify and identify land uses is the best way to understand soil losses throughout the year in the study area. It was possible to observe that agricultural areas are generally associated with greater soil losses in the subwatershed. In addition, the land uses were considered to vary quarterly, thereby making it possible to identify the periods most prone to erosion processes throughout the year. Finally, the erosion percentages in the subwatershed can be linked to the tolerance index for different land-uses, soil classes, and slope categories.

Resumen Escurrimiento superficial en terrenos susceptibles sin asociación con el drenaje adecuado causa erosión del suelo. Las cárcavas y el drenaje son importantes para proyectos de recuperación, ya que la erosión puede ser reactivada después de la aplicación de técnicas de recuperación. Describimos un proyecto de bajo costo para macrodrenaje en Nazareno (MG, Brasil), proporcionando suporte a la gestión y recuperación de cárcavas. Utilizamos una metodología con la aplicación de Sistemas de Información Geográfica (SIG) y modelos hidrológicos y hidráulicos concentrados (softwares libres). La cuenca ha presentado pendientes elevadas (8 a 20%); el flujo de agua es direccionado preferentemente al noroeste, contribuyendo al agravamiento de la erosión. Estudiamos el efecto de condiciones medioambientales en diferentes simulaciones para un proyecto de sistema de drenaje usando las herramientas de softwares. Así pues, los resultados de este artículo pueden auxiliar la gestión y recuperación de cárcavas para esta y otras áreas con problemas similares.

Abstract Runoff on susceptible terrains that is not associated with adequate drainage causes soil erosion, as gullies. Gullies and drainage continue to be major issues in reclamation projects since soil erosion can be reactivated after the application of recovery measures. This paper describes a low-cost project framework for macrodrainage for a gully in Nazareno (MG, Brazil) to provide support to gully management and recovery. We used a simple methodology with the application of Geographic Information Systems (GIS) and concentrated hydrologic and hydraulic models (freely available softwares). The basin has steep slopes (8 to 20%) and the water flows mainly to the northwest, which contribute to exacerbate erosion problems. We studied the effect of environmental conditions on different simulations to elaborate a drainage system project using the free software tools. Therefore, the findings of this paper can aid gully management and recovery for this and other areas with similar issues.