Water erosion is one of the most important soil degradation processes and it can be intensified by land use and vegetal covering changes. Thus, water erosion modeling studies associated to multi temporal analyses of land use are effective in assessing how changes in land cover affects sediment yield. Therefore, considering the modifications in the land use from 1986 to 2011, the aim of this study ranged to estimate water erosion rates and compare them to the soil loss tolerance (SLT) limit in the Latosols (Oxisols) at Ribeirão Caçús sub-basin, in the South of Minas Gerais State, Southeast Brazil, by means of the Revised Universal Soil Loss Equation (RUSLE) in association with the geographic information system (GIS), and geostatistical techniques. So, for each year mapped, soil loss averages were compared by t test at 5% significance to assess the soil degradation stage. The results indicated that, in the period, the soil loss average rate was from 2.4 to 2.6 Mg ha -1 year -1 and the areas with soil loss above the limit of SLT were around 8.0%. The t test demonstrated there was no considerable difference among the soil loss averages (p = 0.18). In consequence, the area of degraded soils did not increase. Thus, the RUSLE model in GIS is a simple and useful tool to estimate the soil loss and help define soil conservation and recovery measures.

INTRODUÇÃOO uso de modelos para a avaliação e mitigação de impactos ambientais é imprescindível frente ao futuro crescimento da população e da demanda por commodities da agropecuária (UNFPA 2012), que deverão acarretar ainda maior pressão sobre os solos. Além disso, no Brasil, 79,6 % da energia elétrica ABSTRACT RESUMO

The increasing demand for food resulting from demographic growth has required more productive agropastoral practices. Consequently, new areas were selected for agropastoral production in an arbitrary way, disregarding land use capacity. This ends up in acceleration of degradation processes, mainly those related to water erosion. In this context, the system of land use capacity proposes the classification of maximum use allowed for land of a rural property or of a hydrographic sub-basin, in an attempt to make sustainable plans of use and management of natural resources. Concerning current use of land, the system indicates the sites where there are conflicts in use in relation to their use capacity. Thus, it is possible to propose measures to adapt land use to its use capacity. Therefore, in this study, the classes of land use capacity at the hydrographic sub-basin of Córrego Pedra Branca, in Alfenas, in the state of Minas Gerais, were evaluated. For that purpose, the following soil parameters were evaluated: effective depth, water permeability, texture, declivity, erosion class, base saturation, effective and potential cationic exchange capacity, and aluminum saturation. Soil analyses presented values of base saturation and of low capacity of effective and potential cationic exchange, which illustrate the low natural fertility of these soils, as well as aluminum saturation level harmful to most cultures. Thus, land use would be restricted to low impact, permanent crops, silvicultures, associated agrosilvipastoral system with conservationist management techniques, as, for example, direct seeding, soil correction and fertilization, and reforestation of permanent preservation areas

Diversas formas de uso e ocupação em áreas urbanas tem ocasionado impactos ambientais negativos em diferentes escalas, sendo um deles a degradação dos recursos hídricos, que tem suscitado novas discussões sobre mecanismos de alteração da água subterrânea rasa. A proposição de estratégias metodológicas eficientes a partir da identificação e dimensionamento de características hidroquímicas da água em determinado espaço geográfico, consiste em desafio oportuno a colaborar para a conservação e uso adequado. Diante desse contexto, o objetivo do trabalho é analisar a qualidade da água no aquífero raso em área urbana Campos dos Goytacazes/RJ, correlacionando com a influência de estruturas urbanas nessa dinâmica. Foram coletadas e analisadas amostras de água de 15 poços, além de dados potenciométricos, a fim de correlacionar fatores como: qualidade da água, tipo de uso por parte da população, influência do cemitério, e hidrodinâmica subsuperficial. Tais poços foram previamente espacializados, seguido da coleta e armazenamento das amostras, análise em laboratório, e interpretação a partir das diferentes variáveis que compuseram o quadro síntese para análise simplificada. Em adição, foi elaborado mapa potenciométrico a partir dos níveis freáticos encontrados, permitindo compilar os parâmetros elencados. Os resultados sugerem que o lençol freático é consideravelmente raso na área estudada, tornando os recursos hídricos mais vulneráveis. Por se tratar de uma área de múltiplos usos, como residencial, agrícola, comercial, além da presença de um cemitério, acaba por expor a região a maiores riscos de contaminação. Destaca-se que, conforme verificado em trabalho de campo, a região possui potenciais agentes poluidores, levando a um maior número de substâncias contaminantes que podem ser liberadas neste ambiente. Adicionalmente, constatou-se alteração dos padrões biológicos, físicos e químicos, com contaminações acima do valor máximo permitido em lei para os seguintes elementos: Fe, Al, Pb, Mn e P, além da presença de Escherichia coli (E. Coli).       Assessment of water quality in a shallow aquifer in Campos dos Goytacazes, Rio de Janeiro, Brazil A B S T R A C TVarious forms of use and occupation in urban areas have caused negative environmental impacts at different scales, one of them being the degradation of water resources, which has given rise to new discussions on mechanisms for altering shallow groundwater. The proposition of efficient methodological strategies based on the identification and dimensioning of the hydrochemical characteristics of water in a given geographic space is an opportune challenge to collaborate for the conservation and proper use. In this context, the objective of this work is to analyze the water quality in the shallow aquifer in urban area Campos dos Goytacazes/RJ, correlating with the influence of urban structures in this dynamic. Water from 15 wells were collected and analyzed, in addition to potentiometric data, in order to correlate factors such as: water quality, type of use by the population, influence of the cemetery, and subsurface hydrodynamics. Such wells were previously spatialized, followed by collection and storage of aggregates, laboratory analysis, and interpretation based on the different variables that made up the synthetic framework for simplified analysis. In addition, a potentiometric map was drawn up from the groundwater levels found, allowing for the compilation of the listed parameters. The results obtained that the water table is considerably shallow in the studied area, making water resources more vulnerable. As it is an area with multiple uses, such as residential, agricultural, commercial, in addition to the presence of a cemetery, it ends up exposing the region to greater risks of contamination. It is noteworthy that, as verified in field work, the region has potential polluting agents, leading to a greater number of contaminants that can be released into this environment. Additionally, there was a change in biological, physical and chemical standards, with contamination above the maximum value allowed by law for the following elements: Fe, Al, Pb, Mn and P, in addition to the presence of Escherichia coli (E. Coli).Keywords: Hydrochemistry; Hydrodynamic; Shallow Aquifer; Contamination.

Since the mid-16th century, the Tietê River has been an important route for the territorial occupation and exploitation of natural resources in the interior of São Paulo and Brazil. Currently, the Tietê River is well known for environmental problems related to water pollution and contamination. However, little attention has been focused on water erosion, which is a serious issue that affects the soils and waters of the hydrographic basin. Thus, this work aimed to estimate soil loss caused by water erosion in this basin, which has an area of approximately 72,000 km², using the Revised Universal Soil Loss Equation (RUSLE). The RUSLE parameter survey and soil loss calculation were performed using geoprocessing techniques. The RUSLE estimated an average soil loss of 8.9 Mg ha-1 yr-1 and revealed that 18% of the basin's territory presents high erosion rates. These are priority zones for conservation practices to reduce water erosion and ensure long-term soil sustainability. The estimated sediment transport was 1.3 Mg ha-1 yr-1, whereas the observed sedimentation, which was calculated based on data from the fluviometric station, was 0.8 Mg ha-1 yr-1. Thus, the results were equivalent considering the large size of the study area and can be used to assist in managing the basin. Estimating soil losses can help in the planning of sustainable management of the Tietê River Hydrographic Basin and highlights the importance of minimizing water erosion, thus helping to prevent additional pollution and contamination with sediments, agrochemicals, and fertilizers.