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Understanding the behavior of the river regime in watersheds is fundamental for water resources planning and management. Empirical hydrological models are powerful tools for this purpose, with the selection of input variables as one of the main steps of the modeling. Therefore, the objectives of this study were to select the best input variables using the genetic, recursive feature elimination, and vsurf algorithms, and to evaluate the performance of the random forest, artificial neural networks, support vector regression, and M5 model tree models in forecasting daily streamflow in Sono (SRB), Manuel Alves da Natividade (MRB), and Palma (PRB) River basins. Based on several performance indexes, the best model in all basins was the M5 model tree, which showed the best performances in SRB and PRB using the variables selected by the recursive feature elimination algorithm. The good performance of the evaluated models allows them to be used to assist different demands faced by the water resources management in the studied river basins, especially the M5 model tree model using streamflow lags, average rainfall, and evapotranspiration as inputs. HIGHLIGHTS The Recursive Feature Elimination was the best input feature selection algorithm.; The machine learning models were efficient in the daily streamflow forecasting.; The performance of the M5 model tree was better than the other models.; The models are potential tools to assist water resources management.;

Changes in precipitation and air temperature may produce different impacts on the hydrological regime, compromising water supply. This study focuses on climate change impacts in the Verde River Basin (VRB), a tropical headwater basin in southeast Brazil, located in the state of Minas Gerais. The Variable Infiltration Capacity model (VIC) was calibrated and validated in the Verde River Basin. The downscaling (Eta Regional Climate Model, at 20-km resolution) of three Global Circulation Models (CanESM2, HadGEM2-ES and MIROC5) were used to drive the VIC for a historical baseline (1961-2005) and three time-slices (2011-2040, 2041-2070 and 2071-2099), under RCPs 4.5 and 8.5 scenarios. The scenarios were used as input in the hydrological model after bias correction. The hydrological model (VIC) showed satisfactory statistical performance in calibration and validation, with CNS varying from 0.77 to 0.85 for daily and monthly discharges; however, it overestimated some peak flows and underestimated the recession flows. Multi-model ensemble means predict increases of the minimum and maximum monthly average temperature for the investigated area at the end of the century. The Eta-CanESM2 indicated greater warming, mainly for RCP8.5 at the end the century, whereas Eta-HadGEM2-ES showed higher reduction in the precipitation for RCP4.5 at the beginning of the century and for RCP8.5 at the end the century, negatively impacting the evapotranspiration and discharge. Among the Regional Climate Models (RCMs), the Eta-MIROC5 showed minor changes in the components of the hydrological cycle. This study suggests that Global Circulation Models represent an additional uncertainty, which should be accounted for in the climate change impact assessment.

The Brazilian Cerrado biome is the largest and richest tropical savanna in the world and is among the 25 biodiversity hotspots identified worldwide. However, the lack of adequate hydrological monitoring in this region has led to problems in the management of water resources. In order to provide tools for the adequate management of water resources in the Brazilian Cerrado biome region, this paper develops the regionalization of maximum, mean and minimum streamflows in the Tocantins River Basin (287,405.5 km2), fully located in the Brazilian Cerrado biome. The streamflow records of 32 gauging stations in the Tocantins River Basin are examined using the Mann-Kendall test and the hydrological homogeneity non-parametric index-flood method. One homogeneous region was identified for the estimate of the streamflows Qltm (long-term mean streamflow), Q90% (streamflow with 90% of exceeding time), Q95% (streamflow with 95% of exceeding time) and Q7,10 (minimum annual streamflow over 7 days and return period of 10 years). Two homogeneous regions were identified for maximum annual streamflow estimation and the Generalized Extreme Value distribution is found to describe the distribution of maximus events appropriately within the both regions. Regional models were developed for each streamflow of each region and evaluated by cross-validation. These models can be used for the estimation of maximum, mean and minimum streamflows in ungauged basins within the Tocantins River Basin within the area boundaries identified. Therefore, the results provided in this paper are valuable tools for practicing water-resource managers in the Brazilian Cerrado biome

The Soil Conservation Service Curve Number Model is a conceptual model intended for estimating effective rainfall (ER). This model is grounded in a parameter – referred to as Curve Number (CN), which is determined from information on the characteristics of the watershed. The Standard Method (M1) for determining the CN is based on soil and land-use tables; however, some authors have proposed alternative methodologies for defining the CN value from monitored rainfall-runoff events, such as those described by Hawkins (1993) (M2), Soulis and Valiantzas (2012) (M3), and Soulis and Valiantzas (2013) (M4). The objective of this study was to evaluate the impact of using these methods for determination of the CN parameter on the estimation of ER, taking as reference forty rainfall-runoff events monitored between 2015 and 2018 in the Cadeia River Watershed, which has characteristics of the Pampa biome. The different methods assessed for definition of the CN parameter resulted in contrasting performances with respect to the estimation of ER for CRW, as the following findings: i) M1 gave ER values with little reliability, mainly due to the classification of antecedent moisture content classes; ii) M3 provided the best results in determining ER, followed by M2; and iii) the ER values estimated according to M4 differed from those observed, mainly for events with lower rainfall depths.

The Brazilian Cerrado biome (BCB) is among 25 biodiversity hotspots identified worldwide, and covers the recharge area of important aquifers and rivers in South America. The increase in deforestation has been threatening water availability in this region. In order to assist in the water-resource management of the BCB, this study models the daily streamflow in a basin of the Cerrado, using two approaches: a process-based model (Soil and Water Assessment Tool - SWAT) and the data-driven model (Artificial Neural Network - ANN). The performance of the models was evaluated by the Nash-Sutcliffe coefficient (NSE), coefficient of determination (R2) and flow-duration-curves (FDC). The results indicate that SWAT (NSE > 0.61; R2 > 0.68) and ANN (NSE > 0.91; R2 > 0.79) models are suitable tools in daily streamflow modeling of the studied basin, with the ANN model being the most accurate. Based on FDC, the ANN model was also better than the SWAT model for all frequencies evaluated. Thus, the ANN model is a promising new approach for daily streamflow modelling in this region. Moreover, the results of this study can help water-resource managers in planning and implementing appropriate water allocation and conservation measures in the Brazilian Cerrado biome.

Successful streamflow forecasts depend on an adequate performance evaluation of the hydrological model. In this study, the hydrological responses were compared using two hydrological models, physic-based and semi-distributed, Soil and Water Assessment Tool (SWAT) and Variable Infiltration Capacity (VIC), using input data from the Verde River Watershed, located in the Minas Gerais state in southern Brazil. This is a study of one of the most important headwater watershed regions of Brazil (Mantiqueira Range). Both models were suitable for streamflow simulation, with values of R2 (determination coefficient) and NSE (Nash-Sutcliffe) higher than 0.8, NSELog higher than 0.35 (Nash–Sutcliffe Efficiency of the logarithmic values of discharge) and PBIAS (percentage deviation) less than 25%. The integration of SWAT and VIC models can be useful in different water-resource assessment studies. Therefore, based upon this study further investigations should be conducted using various hydrological models and climate, land-use and land-cover changes scenarios in the region.

Maximum and minimum streamflow are fundamental for water resource management, especially for water rights. However, lack of monitoring and scarce streamflow data limit such studies. Streamflow regionalization is a useful tool to overcome these limitations. The study developed models for regionalization of the maximum and minimum reference streamflows for the Mortes River Basin (MRB) (Water Resources Planning and Management Unit - GD2), Southern Minas Gerais State. The study used long-term streamflow historical series provided by the Brazilian National Water Agency (ANA). Previous exploratory analysis was performed, and it was observed that the streamflow series are stationary according to the Mann-Kendall test. The estimation of the streamflow for different return periods (RP) was performed by fitting Probability Density Functions (PDFs) that were tested by the Anderson-Darling (AD) test. The Generalized Extreme Values (GEV) and Wakeby were the most appropriate PDFs for maximum and minimum streamflows, respectively. The streamflow models were fitted using a power regression procedure, considering the drainage area of the watersheds as inputs. The fittings reached the coefficient of determination (R2) greater than 0.90. Thus, the streamflow regionalization models demonstrated good performance and are a potential tool to be used for water resource management in the studied basin.

ABSTRACT Since prolonged droughts have impacted Atlantic forests in Southeastern Brazil, further investigations to understand the effects of such stressful conditions in their hydrological behavior are required. This study aimed to assess the changes in the water balance of a semi-deciduous Atlantic forest remnant and how the forest responds to droughts. The Standardized Precipitation-Evapotranspiration Index was applied to identify droughts (from 1961 to 2019) and their severity in both the hydrological year and summer scales. Drought impacts on actual evapotranspiration, potential percolation, and soil water storage were assessed using Hydrus-1D, having net precipitation and potential evapotranspiration as inputs. Error analyses (< 10%) confirmed Hydrus-1D suitability for simulating soil moisture. Uncertainties regarding the soil saturated hydraulic conductivity are due to preferential flows, which are not accounted for in Richards’ equation. Drought intensification changed forest hydrology and triggered physiological responses to deal with it. Semi-deciduous Atlantic forests are adapted to dry conditions because of the existence of dry-affiliated species and the activation of physiological mechanisms. However, such adaptations responded differently regarding the drought scales. The intensification of summer droughts increased evapotranspiration and decreased the potential percolation. Leaf shedding changed the canopy structure in a two-year time lag as a response to the intensification of hydrological year droughts. Changes in forest hydrology are sudden and trigger physiological responses, such as leaf shedding, in a delayed process after droughts take place.

ABSTRACT Globally, soil degradation by water erosion has become one of the major environmental problems in tropical regions, especially under the severe environmental conditions of the Andes. This study aims to detail the soil risk to degradation by water erosion in a water producer basin located in the Tropical Colombian Andes (Combeima River basin), applying the RUSLE model, discussing how to minimize the erosion processes under its environmental conditions (steep slope, climatic variability, soil classes and properties diversity, and alternative land uses). RUSLE was applied with the support of GIS to estimate current and potential risk to soil erosion in the basin, allowing the identification of areas more prone to degradation. It was found that currently, 50.5% of the basin’s area presents, on average, annual soil losses greater than 25 Mg ha-1 yr-1, meaning a very high risk to water erosion, with 30.4% showing a severe risk (> 100 Mg ha-1 yr-1). It was possible to conclude that the current land uses and soil management systems have not been effective in mitigating soil erosion, mainly when situated in steep topography. Therefore, it is necessary sustainable planning for the conservation of soil, water, organic carbon, plant nutrients, and other elements (not-nutrients) in this tropical Andes region.

Abstract Mathematical models have been widely used to quantify hydrological processes for various practical purposes. These models depend on geomorphological attributes which are derived from relief information represented by Digital Elevation Models (DEM). The objective of this study was to evaluate the influence of relief information sources (ASTER, SRTM-30, SRTM-90, and TOPO) over geomorphological characterization of five Brazilian watersheds. Geoprocessing tools were applied for extraction of the following geomorphological attributes for each DEM: drainage area, perimeter, and watershed slope; length and slope of the main stream; total length of streams; bifurcation, stream length and stream area ratios; and length of the highest order stream. The differences in the values of attributes were calculated in relation to the reference DEM (TOPO). It was found that: i) slope of main stream and bifurcation ratio were the most sensitive parameters regarding the relief information source; ii) flat watersheds were more susceptible to altimetric errors; iii) ASTER did not adequately represent drainage networks for flat watersheds; and iv) the differences in the geomorphological attributes increased as drainage area decreased. The results indicate that DEM may exert influence on the use of hydrological models that depend on geomorphological attributes.

ABSTRACT Hydrosedimentological modeling is a useful tool to predict the water dynamic in a basin and for water resources management. This study aimed to i) evaluate the ability of Soil and Water Assessment Tool (SWAT) to model sediment load and continuous monthly streamflow in the Mortes River Basin (MRB) in Southeastern Brazil; ii) estimate the sediment yield spatially distributed by sub-basins; iii) estimate the sediment load export to the Funil Hydroelectric Power Plant reservoir (FHPP), located in the MRB outlet. For the sensitivity analysis, calibration, and uncertainty analysis of the model, a semi-automatic calibration in SWAT-CUP version 5.1.6 software with the “Sequential Uncertainty Fitting” algorithm was used. To evaluate the ability of SWAT to reproduce the continuous MRB monthly streamflow and sediment load, statistical indexes, and graphical analyses were used to compare the simulated and observed data. For the sediment evaluation, a spatial and temporal comparison of sediment yield maps was used as well as the sediment yield observed in sub-basins, aiming to identify the areas with a more significant contribution to the sediment generation in the basin. The results demonstrated that SWAT performed satisfactorily in simulating both monthly sediment load and streamflow. For discharge calibration, 99 % of the measured data were bracketed by the 95 % prediction uncertainty (95PPU), and for validation, 97 % of the data were bracketed by the 95PPU, which indicates proper bracketing of the measured data within model prediction uncertainty. Uncertainty analysis indicated that 95PPU could capture 78 % of the sediment loads measured during the calibration and 72 % of the measured data during the validation period at MRB. The hydrologic response unit with pasture and Argissolos (Ultisols), Neossolos Litólicos (Entisols), and Cambissolos (Inceptisols) combined with undulated relief were the main areas responsible for the highest sediment contributions. The sediment load delivered to the reservoir from its filling 2002 to 2015 was estimated in 6,682,704 m3 (16,706,761 Mg) (density of 2.5-Mg m-3) which value corresponded to 2.6 % of storage capacity (water plus sediment) in 14 years. These results are strategic since to become feasible identifying priority areas for soil and water conservation practices as well as useful information for water resources planning and management in the studied basin.

Projetos hidráulicos e a gestão da água demandam dados hidrológicos confiáveis. A bacia hidrográfica do rio Araguaia-Tocantins, além do uso agrícola, apresenta grande potencial para exploração hidroelétrica. No entanto, a rede de monitoramento fluviométrico na bacia hidrográfica do rio Araguaia apresenta densidade reduzida de estações, o que implica na falta de dados hidrológicos. A regionalização de vazões de referência é uma técnica que pode ajudar a contornar essa insuficiência de dados, propiciando a estimativa de vazões a partir de variáveis explicativas de fácil obtenção. Neste contexto, objetivou-se desenvolver funções regionais para vazão máxima (Qmax) aplicáveis a diferentes Períodos de Retorno (RP), vazão média em longo prazo (Qmlt) e vazão com 95% de permanência (Q95) para as sub-bacias de alto e médio curso do rio Araguaia. Adotou-se a metodologia da vazão adimensional e a área de drenagem como variável explicativa. Os modelos regressivos testados foram o linear, potencial e quociente. Empregou-se para verificação da qualidade dos modelos regionais a validação-cruzada leave-one-out. Utilizou-se 10 distribuições estatística de 2 a 5 parâmetros. (i) Obtiveram-se resultados satisfatórios para todas as vazões de referência. (ii) A técnica de validação cruzada mostrou-se essencial para a seleção do modelo mais robusto. (iii) O modelo de quociente mostrou-se superior ao modelo potencial e linear na maioria dos casos.

Hydroelectricity is responsible for the greatest fraction of the electric energy generated in Brazil. The water footprint of hydropower plants (WFP) is an important indicator of the sustainable and efficient use of water resources. In this context, WFP of the Sobradinho Hydropower Plant was determined for the period from 2003 to 2012, taking into account the reservoir’s historical variation for the flooded area. To accomplish this, monthly series of electric energy production, flooded area, evaporation and evapotranspiration rates were used. Average gross and net evaporation were 2,031 and 1,577 mm year-1, respectively. The average power generation of this facility in the analyzed period was 462 MW, and the flooded area of its reservoir presented an average value of 3,054 km². Based on the monthly data, the gross and net water footprints were, respectively, 417 and 325 m³ GJ-1. Based on these results, it can be concluded that the changes in the reservoir’s area exert direct and important influence on the WFP estimates of the Sobradinho hydropower plant. The WFP estimates in this study were different from other studies that adopted a constant value of 4,214 km² for this reservoir’s area, which is taken based on the normal water level of the plant operation.

In order to design effective Brazilian hydraulic structures, it is necessary to obtain data relating to short-duration intense rainfall from historical series of daily rainfall. This recurring need can be fulfilled by rainfall disaggregation methodology. The objective of this study was to determine the intense rainfall disaggregation constants for the State of Tocantins and to compare these constants with those obtained for other regions of Brazil. For the modeling of the frequency of intense rainfall of different durations of less than 24 hours, the Gumbel probability distribution (GPD) was employed using rainfall series from 10 locations in Tocantins state. The results showed that the GPD was adequate by the Kolmogorov-Smirnov and Chi-square tests. The disaggregation constants presented low variability values for different return periods (from 10 to 100 years); the values for Tocantins state are: h12h/h24h=0.93, h6h/h24h=0.86, h4h/h24h=0.82, h3h/h24h=0.78, h2h/h24h=0.72, h1h/h24h=0.61, h50min/h1h=0.92, h40min/h1h=0.83, h30min/h1h=0.68, h20min/h30min=0.76 e h10min/h30min=0.46. The comparison of the results with those from studies developed for other Brazilian regions showed variations of up to -62.30%, allowing us to conclude that the use of local constants is important in the process of rainfall disaggregation.

ABSTRACT Brazil is a large country that depends on the hydroelectricity generation hydropower dams. The Upper Grande River Basin (UGRB) is one of the most important Brazilian hydrological regions in terms of water availability and electric energy production. Therefore, studies of water availability are indispensable for a better and more successful decision making in water resources management in the region. This study objective to approach the land-use influence on the soil hydrology in the Upper Grande River Basin, a strategic headwater basin of southeastern Brazil. This study uses hydrological indicators (baseflow/runoff (BF/R) and overland flow/runoff (OF/R)) extracted from eight watersheds, varying the size and localization in the region, to support the results found. Soil saturated hydraulic conductivity (Ko) was determined in situ using a constant flow permeameter, totaling 224 sampled points. Five machine learning algorithms were compared in their performance to predict Ko (Random Forest, Support Vector Machine, Gradient Boosting, Linear Regression, Regularization) using terrain attributes as covariates. The tested methods for predicting Ko resulted in a relatively low coefficient of determination (R2) due to the high spatial variability of this soil hydrologic attribute. The hydrological indicator BF/R was sensitive to land-use changes in the watersheds. The greatest Ko values were associated with native forest and the least values area associated with pasture and rupestrian field.

This study was carried out in an Atlantic forest remnant in Southeastern Brazil and aimed to spatially model the soil water content (SWC) and net precipitation (NP) on a monthly time scale and to assess the spatial behavior of these hydrological variables in the different seasons. NP is defined by summing throughfall and stemflow, which have been collected after each rain event and accumulated monthly. Soil moisture measurements were carried out monthly up to a depth of 1.00 m and then integrated to obtain the SWC. The exponential semivariogram model was fitted for both hydrological variables, and the goodness-of-fit was assessed by a cross-validation procedure, spatial dependence degree (SDD) and spatial dependence index (SDI). This model provided adequate performance for SWC and NP mapping according to the cross-validation statistics. Based on the SDD, both variables have been classified as a ‘strong spatial dependence structure’. Nevertheless, when the SDI was assessed, NP showed less spatial dependence, while the SWC maintained almost the same performance. Kriging maps pictured the regional climate seasonality due to higher values of both variables in spring and summer than in autumn and winter seasons. However, correlations between NP and SWC are not expressive in the studied period.

The free aquifer recharge is a process of major importance in groundwater hydrology because it represents the renewable reserves of the water source. A good estimate of this variable is therefore critical to the proper management of water resources, particularly in light of climate variability inherent to the climate regime, as well as the increasing of surface water pollution and increased demand for good quality water groundwater. This study used a water balance model in soil to estimate the potential recharge (Rp) of the unconfined aquifer and the other components of the hydrological cycle. The model was applied in two watershed headwaters of the Rio Grande in Minas Gerais, Brazil: the Lavrinha River Basin (BHRL) and the Marcela River Basin (BHRM). The BHRL presents higher values of Rp, with an annual average of 895 mm, which corresponds to 40% of rainfall, while at the BHRM these values were 393.3 mm and 25%, respectively. The base runoff values confirm the greater recharge in BRHL, where this hydrograph component corresponded to 76% of the total discharge, compared with 40% for BHRM. The BALSEQ model allowed us to capture this difference, but the results were satisfactory for only one of the years in the BHRL and for the entire period for the BHRM, which reinforces the need to use this model for long time periods.

ABSTRACT The application of quantitative methods to digital soil and geomorphological mapping is becoming an increasing trend. One of these methods, Geomorphons, was developed to identify the ten most common landforms based on digital elevation models. This study aimed to make a quantitative assessment of the relationships between Geomorphons units, determined at three spatial resolutions and nine radii, and soil types and properties of two watersheds with different soil-landscape relationships in Brazil to help soil surveying and mapping under tropical conditions. The study was conducted at Lavrinha Creek (LCW) and Marcela Creek (MCW) watersheds, located in the state of Minas Gerais, Brazil. Spatial resolutions of 10, 20 and 30 m were the basis for generating Geomorphons at 9 radii of calculation for the watersheds. They were overlapped to detailed soil maps of the watersheds and a chi-square test was carried out to assess their relationship with soil types. Observation points were compared with the most highly correlated Geomorphons to also assess relationships with soil properties. Geomorphons with resolution of 30-m and radii of 20 and 50 cells, respectively for LCW and MCW, were more highly correlated with the variability of soil types, in accordance with the terrain features of these watersheds. The majority of observation points for each soil type was located in the same Geomorphon unit that was dominant when analyzing soil maps. There was less variability in soil properties between Geomorphon units, which was probably due to the highly weathered-leached stage of soils. Geomorphons can help to improve soil maps in tropical conditions when assessing soil variability due to its high correlation with tropical soil types variability.

ABSTRACT This study compared the performance of ordinary kriging (OK) and regression kriging (RK) to predict soil physical-chemical properties in topsoil (0-15 cm). Mean prediction of error and root mean square of prediction error were used to assess the prediction methods. Two watersheds with contrasting soil-landscape features were studied, for which the prediction methods were performed differently. A multiple linear stepwise regression model was performed with RK using digital terrain models (DTMs) and remote sensing images in order to choose the best auxiliary covariates. Different pedogenic factors and land uses control soil property distributions in each watershed, and soil properties often display contrasting scales of variability. Environmental covariables and predictive methods can be useful in one site study, but inappropriate in another one. A better linear correlation was found at Lavrinha Creek Watershed, suggesting a relationship between contemporaneous landforms and soil properties, and RK outperformed OK. In most cases, RK did not outperform OK at the Marcela Creek Watershed due to lack of linear correlation between covariates and soil properties. Since alternatives of simple OK have been sought, other prediction methods should also be tested, considering not only the linear relationships between covariate and soil properties, but also the systematic pattern of soil property distributions over that landscape.

A condutividade hidráulica saturada do solo (K0) é de grande importância para a hidrologia, especialmente no contexto da infiltração, onde apresenta grande influência nas condições de geração de escoamento superficial direto, tendo como consequências a formação de inundações, erosão do solo e transporte de sedimentos. Além disso, tem papel fundamental na agricultura, por contribuir na infiltração e disponibilização de água para as plantas, e também na conservação do solo e do meio ambiente. Diante do exposto, o objetivo deste trabalho foi estimar e analisar o comportamento da condutividade hidráulica saturada do solo associada aos seus atributos físicos e declividade e avaliar o escoamento superficial direto, em uma área de floresta de Cedrus deodara, em Madrid, na Espanha. Para tanto, foram realizados testes de infiltração com o método dos anéis concêntricos em três pontos na área de estudo, a fim de obter dados que foram ajustados pelo modelo de Horton para estimar a condutividade hidráulica saturada do solo, e também foram realizados testes com um simulador de chuvas a fim de determinar o coeficiente de escoamento superficial. Foram retiradas amostras deformadas do solo para determinação de seus atributos físicos. Os resultados mostraram que o modelo de Horton foi adequado para estimar a condutividade hidráulica saturada do solo. Os valores dos atributos físicos do solo e a declividade influenciaram a condutividade hidráulica saturada do solo. A matéria orgânica associada à declividade do solo proporcionaram os maiores valores de K0. O escoamento superficial direto apresentou relação inversa à condutividade hidráulica saturada do solo.

ABSTRACT Models have been used by man for thousands of years to control his environment in a favorable way to better human living conditions. The use of hydrologic models has been a widely effective tool in order to support decision makers dealing with watersheds related to several economic and social activities, like public water supply, energy generation, and water availability for agriculture, among others. The purpose of this review is to briefly discuss some models on soil and water movement on landscapes (RUSLE, WEPP, GeoWEPP, LASH, DHSVM and AnnAGNPS) to provide information about them to help and serve in a proper manner in order to discuss particular problems related to hydrology and soil erosion processes. Models have been changed and evaluated significantly in recent years, highlighting the use of remote sense, GIS and automatic calibration process, allowing them capable of simulating watersheds under a given land-use and climate change effects. However, hydrology models have almost the same physical structure, which is not enough for simulating problems related to the long-term effects of different land-uses. That has been our challenge for next future: to understand entirely the hydrology cycle, having as reference the critical zone, in which the hydrological processes act together from canopy to the bottom of aquifers.

Compreender as correlações existentes entre variáveis ambientais e a distribuição das espécies em uma floresta, sua dinâmica e estoque de carbono é um dos principais objetivos em ecologia florestal. Nesse sentido o presente trabalho objetivou correlacionar aspectos da vegetação com variáveis topo-edafo-climáticas em um remanescente florestal em Bocaina de Minas, Serra da Mantiqueira, MG. Técnicas multivariadas de ordenação (PCA e CCA) e regressões múltiplas foram utilizadas para representar essas correlações. Altitude teve destaque como fator ambiental síntese, compreendendo vários gradientes existentes na área (em especial edáfico e de conservação) sendo, portanto, a variável que mais explicou distribuição de espécies, dinâmica florestal e estoque de carbono na área.

The estimation of surface flow into direct surface flow and base flow is fundamental for understanding the hydrologic behavior of basins, being possible, among other features, the capability of discharges maintenance during the dry seasons. Analysis of the related base flow with hydrogeological classes can contribute to understand the hydrological processes involved. This work aimed to estimate the base flow for eight fluviometric stations that were chosen according to the hydro geologic systems observed in the State of Minas Gerais. A numerical filter was employed in order to evaluate the relationship between hydrogeology and water flow regime. Daily discharge data sets, between October/1981 and September/1991, were used in the study. In all cases, the base flow accounted for over 50% of the water flow in rivers. The hydrogeological systems "xistosa", "pelítica" and "cobertura detrítica" presented smaller amount of base flow in the rivers discharge than other hydrogeological systems and obtained the same statistical classification. Based on the results we concluded that hydrogeology exerts indirect influence on the relationship between the base flow and river discharge.

ABSTRACTUnderstanding soil formation processes across different landscapes is needed to predict how soil properties will respond to land use change. This study aimed to characterize mountainous Inceptisols (Cambisols) under high altitude subtropical climate in southeastern Brazil, by soil physical, chemical and micromorphological analyses, under native forest and pasture. The soil under pasture had a greater bulk density than under forest, resulting in a severe reduction of macroporosity. At two depths, coarse quartz grains are angular, suggesting absence of transportational processes, thus confirming an autochthonous pedogenesis from the underlying gneissic rock. Most feldspars were weathered beyond recognition, but mineral alteration was commonly seen across cleavage plans and edges of micas. The micromorphological results suggest an intermediate stage of mineral weathering and soil development, which is in accordance with properties expected to be found in Inceptisols.

Study region: The study was conducted in the Rio Grande do Sul state – Brazil. Study focus: Studies about heavy rainfall events are crucial for proper flood management in river basins and for the design of hydraulic infrastructure. In Brazil, the lack of runoff monitoring is evident, therefore, designers commonly use rainfall intensity–duration–frequency (IDF) relationships to derive streamflow-related information. In order to aid the adjustment of IDF relationships, the probabilistic modeling of extreme rainfall is often employed. The objective of this study was to evaluate whether the GEV and Kappa multiparameter probability distributions have more satisfying performance than traditional two-parameter distributions such as Gumbel and Log-Normal in the modeling of extreme rainfall events in southern Brazil. Such distributions were adjusted by the L-moments method and the goodness-of-fit was verified by the Kolmogorov–Smirnov, Chi-Square, Filliben and Anderson–Darling tests. New hydrological insights for the region: The Anderson–Darling and Filliben tests were the most restrictive in this study. Based on the Anderson–Darling test, it was found that the Kappa distribution presented the best performance, followed by the GEV. This finding provides evidence that these multiparameter distributions result, for the region of study, in greater accuracy for the generation of intensity–duration–frequency curves and the prediction of peak streamflows and design hydrographs. As a result, this finding can support the design of hydraulic structures and flood management in river basins.

The Normalized Difference Vegetation Index (NDVI) is often used to extract information from vegetated areas since it is directly related to vegetation parameters such as percent of ground cover, photosynthetic activity of the plant and leaf area index. The aim of this paper was to analyze the potencial of semivariograms generated from NDVI values to detect changes in vegetated areas, analyzing their behavior (shape) and derived metrics (range, sill and nugget). Semivariograms were generated from NDVI values derived from Landsat TM images of May 2010, June 2010 and July 2011. The study area is located in the northern state of Minas Gerais, Brazil, and is covered by Brazilian savannas vegetation, totalizing 1,596 ha. Semivariograms were generated after the exploratory data analysis. Models were fitted, validated and their metrics analyzed. The results showed a very clear trend where the shape of semivariograms, sill and range were different when deforestation occurred and were similar when the area had not been changed. The model that generated best fit was the Gaussian, however, the three models tested showed behavior that makes it possible to detect changes in vegetation. It suggests that further researches should explore the degree to which the semivariogram can be used to quantify this spatial variability as well as to analyze the influence of sazonality for changing detection in vegetated areas.

ABSTRACT The scarcity of field data to develop soil maps through a pedological survey is one of the main limitations to using distributed hydrological models, especially in small and medium-sized watersheds. The aim of this study was to compare a distributed hydrological model prediction to a soil map based on a pedological survey and a moisture zone map obtained using the Height Above the Nearest Drainage - HAND model. The Distributed Hydrology Soil Vegetation Model - DHSVM, which is a physically-based and distributed hydrological model, was applied to a mountainous watershed, located in the region of the Mantiqueira Range in the south of Minas Gerais in southeastern Brazil, and was compared to both maps mentioned above, taking the soil map developed by the pedological survey as a reference. Daily weather and streamflow data-sets were used for DHSVM calibration and validation using the two different maps (soil and moisture zone maps) as inputs. In both simulations, the DHSVM performed well, with outputs indicating a good relationship between topographical and hydrological characteristics from the two types of maps. Thus, the moisture zone map obtained by the HAND model can also be successfully used in distributed hydrological modeling, especially for mountainous regions in southeastern Brazil.

Soil moisture temporal variability is an important concept in understanding forest management. The objective of this study was to analyse the effect of planting density on soil profile moisture in a clonal Eucalyptus plantation. Soil moisture was observed every 15 days at 25 points distributed throughout the eucalyptus stand between November 2013 and October 2015 to characterize the moisture according to the following three types of spacings: 3 x 2, 3 x 3, and 3 x 5 m. At each point, the 0 - 10, 10 - 20, 20 - 30, 30 – 40, and 60 - 100 cm layers were evaluated using a Profile Probe PR2 model. Soil moisture showed high spatial variability in the 0 - 10 cm layer, whereas from 30 to 100 cm deep, the moisture tended to become more homogeneous throughout the area. The dry periods presented greater temporal soil moisture stability when compared to the rainy seasons. The 3 x 2 m spacing has greater temporal soil moisture stability when compared to the others, while the 3 x 3 m spacing presented greater temporal variability.

http://dx.doi.org/10.5902/1980509815739The analyze of pluvial precipitation and its interaction on the different hydrologic cycle phases in forested watersheds are essential in order to water balance characterization due to its relevant participation in the hydrological processes and to its spatial-temporal variability as function of edaphic, topographic, climatic and vegetation elements. Due to heterogeneity of Atlantic Forest associated to temporal and spatial variability of pluvial precipitation regime, the study of mechanisms that allow describing and linking the hydrological cycle elements are very important. This way, the objective of this study was to analyze the partitioning of pluvial precipitation at a micro-catchment entirely occupied by Atlantic Forest remnant, in Mantiqueira Range, during 2009/2010 and 2010/2011 hydrological years, relating it with the seasonal evolution of this ecosystem which was monitored by the application of normalized difference vegetation indexes (NDVI). It was observed greater percentage of internal pluvial precipitation during the periods with less rainfall. It was also verified greater water storage capacity of the Atlantic Forest’s canopy throughout rainy season. Yet, a plausible correlation was obtained between water storage capacity of Atlantic Forest and the regeneration of vegetation demonstrated by NDVI what can be associated to the processes responsible for Atlantic Forest’s growth.

Solum depth and its spatial distribution play an important role in different types of environmental studies. Several approaches have been used for fitting quantitative relationships between soil properties and their environment in order to predict them spatially. This work aimed to present the steps required for solum depth spatial prediction from knowledge-based digital soil mapping, comparing the prediction to the conventional soil mapping approach through field validation, in a watershed located at Mantiqueira Range region, in the state of Minas Gerais, Brazil. Conventional soil mapping had aerial photo-interpretation as a basis. The knowledge-based digital soil mapping applied fuzzy logic and similarity vectors in an expert system. The knowledge-based digital soil mapping approach showed the advantages over the conventional soil mapping approach by applying the field expert-knowledge in order to enhance the quality of final results, predicting solum depth with suited accuracy in a continuous way, making the soil-landscape relationship explicit.

Probabilistic studies of hydrological variables, such as heavy rainfall daily events, constitute an important tool to support the planning and management of water resources, especially for the design of hydraulic structures and erosive rainfall potential. In this context, we aimed to analyze the performance of three probability distribution models (GEV, Gumbel and Gamma two parameter), whose parameters were adjusted by the Moments Method (MM), Maximum Likelihood (ML) and L - Moments (LM). These models were adjusted to the frequencies from long-term of maximum daily rainfall of 8 rain gauges located in Minas Gerais state. To indicate and discuss the performance of the probability distribution models, it was applied, firstly, the non-parametric Filliben test, and in addition, when differences were unidentified, Anderson-Darlling and Chi-Squared tests were also applied. The Gumbel probability distribution model showed a better adjustment for 87.5% of the cases. Among the assessed probability distribution models, GEV fitted by LM method has been adequate for all studied rain gauges and can be recommended. Considering the number of adequate cases, MM and LM methods had better performance than ML method, presenting, respectively, 83% and 79.2% of adequate cases.

Soil erosion is one of the most significant environmental degradation processes. Mapping and assessment of soil erosion vulnerability is an important tool for planning and management of the natural resources. The objective of the present study was to apply the Revised Universal Soil Loss Equation (RUSLE) using GIS tools to the Verde River Basin (VRB), southern Minas Gerais, in order to assess soil erosion vulnerability. A annual rainfall erosivity map was derived from the geographical model adjusted for Southeastern Brazil, calculating an annual value for each pixel. The maps of soil erodibility (K), topographic factor (LS), and use and management of soils (C) were developed from soils and their uses map and the digital elevation model (DEM) developed for the basin. In a GIS environment, the layers of the factors were combined to create the soil erosion vulnerability map according to RUSLE. The results showed that, in general, the soils of the VRB present a very high vulnerability to water erosion, with 58.68% of soil losses classified as "High" and "Extremely High" classes. In the headwater region of VRB, the predominant classes were "Very High" and "Extremely High" where there is predominance of Cambisols associated with extensive pastures. Furthermore, the integration of RUSLE/GIS showed an efficient tool for spatial characterization of soil erosion vulnerability in this important basin of the Minas Gerais state.

O objetivo deste trabalho foi avaliar tendências das temperaturas mínimas e máximas no Estado de Minas Gerais. Foram avaliados dados de 43 municípios, tendo-se considerado as escalas anual e sazonal - janeiro, abril, julho e outubro, que representam os meses centrais de verão, outono, inverno e primavera, respectivamente. Séries históricas de temperaturas mínimas e máximas do ar diárias, com extensão mínima de 30 anos, foram analisadas com base no teste de Mann-Kendall e no uso de regressão linear simples. As tendências foram consideradas significativas somente quando ambas as avaliações foram significativas; neste caso, determinaram-se as taxas de alteração das temperaturas. Houve boa concordância entre os testes de significância para a detecção de tendências nas séries históricas, na maioria dos municípios. Observou-se tendência de elevação das temperaturas mínimas em julho de até 1,5ºC por década, com tendências generalizadas de aumento na maior parte do estado, em outubro e janeiro, e também na escala anual. Exceções foram verificadas especialmente em municípios de maiores altitudes, em que as temperaturas mínimas diminuíram no inverno. Há predominância de municípios com tendência significativa de aumento de temperaturas, independentemente da escala de avaliação. Tendências de aumento nas temperaturas são esperadas mais comumente no sentido sul-norte do Estado de Minas Gerais.

A erosividade das chuvas é um dos principais agentes causadores da erosão do solo, no sul de Minas Gerais. Por essa razão, objetivou-se, com este trabalho, aplicar cinco distribuições de probabilidades aos valores de erosividades, mensais e anual, e estimar o tempo de recorrência desses valores, com base na melhor distribuição de probabilidades ajustada para a região de Lavras, MG. A série de precipitações estudada foi de 1961 a 2004 e as distribuições de probabilidades utilizadas foram: Gumbel, Gama, Log-normal 2 e 3 parâmetros e Normal, ajustadas pelo método da Máxima Verossimilhança. Verificou-se que as distribuições Gama e Gumbel produziram o menor número de séries não adequadas, registrando-se apenas uma, para o mês de agosto. As demais distribuições produziram maiores números de séries não adequadas, especialmente, a distribuição Log-normal 2 parâmetros. Sendo assim, recomenda-se, para o cálculo de erosividade, que seja feita uma verificação prévia da melhor distribuição para cada período da série estudada, apesar de os dados apontarem um desempenho considerável da distribuição Gumbel.

O objetivo deste trabalho foi determinar os valores de erosividade e gerar os mapas da distribuição espaço-temporal das chuvas no Estado do Tocantins. Analisaram-se séries históricas pluviométricas de 97 postos pluviométricos, compreendendo o período de 1985 a 2009. A erosividade foi estimada por meio de equações nas quais a variável independente foi a precipitação média mensal ou o coeficiente de chuva de Fournier (Rc). A geoestatística foi aplicada para o mapeamento da erosividade tanto na escala mensal quanto na anual. A erosividade anual apresentou valores entre 6.599 e 14.000 MJ mm ha-1 h-1, com auge em dezembro, quando atingiu valores de até 2.800 MJ mm ha-1 h-1 por mês. De maio a setembro, a erosividade apresentou valores inferiores ao crítico, tido como 500 MJ mm ha-1 h-1 por mês. Foram identificadas três regiões prioritárias para ações de planejamento visando a conservação do solo e da água: região centro-oeste do Estado, nas imediações do Parque Estadual do Cantão, com maior erosividade anual; região norte do Estado, especialmente no primeiro trimestre; e região sudeste do Estado, no quarto trimestre.

Ecological indicators have become important tools for assessment and monitoring of natural resources, being the understanding of the relationship between antropic activities and the environmental response essential for their structuring. Although the development of potential indicators may prove sensitive to many variables, they must demonstrate their ability to take the surrounding conditions, from those relatively preserved to those highly disturbed. Based on this premise, the development of the Hydrossedimentological DisturbanceIndex (HSDI) for environmental assessment at watersheds in Minas Gerais state, emerges as a potential tool to support decisions which should be focused on the improvement of natural resources management. A HSDI proposal was developed from the hydrological, climate and water quality database available in Minas Gerais state, highlighting sediment transport (ST), hydrological stress (HS), groundwater recharge (Rec) and current soil erosion potential (SEP), working with a robust tool for determining the weights of factors with appropriate scientific background and subsequent development of map for analyzing its distribution, having Paraopeba river watershed as study case.

The analyze of pluvial precipitation and its interaction on the different hydrologic cycle phases in forested watersheds are essential in order to water balance characterization due to its relevant participation in the hydrological processes and to its spatial-temporal variability as function of edaphic, topographic, climatic and vegetation elements. Due to heterogeneity of Atlantic Forest associated to temporal and spatial variability of pluvial precipitation regime, the study of mechanisms that allow describing and linking the hydrological cycle elements are very important. This way, the objective of this study was to analyze the partitioning of pluvial precipitation at a micro-catchment entirely occupied by Atlantic Forest remnant, in Mantiqueira Range, during 2009/2010 and 2010/2011 hydrological years, relating it with the seasonal evolution of this ecosystem which was monitored by the application of normalized difference vegetation indexes (NDVI). It was observed greater percentage of internal pluvial precipitation during the periods with less rainfall. It was also verified greater water storage capacity of the Atlantic Forest’s canopy throughout rainy season. Yet, a plausible correlation was obtained between water storage capacity of Atlantic Forest and the regeneration of vegetation demonstrated by NDVI what can be associated to the processes responsible for Atlantic Forest’s growth.

The use of a large number of water quality indicators increases the costs of streamflow monitoring throughout the time. Principal Component Analysis (PCA) can be considered a promised tool for water resources management, allowing a reduction in the dimensionality of the data and facilitating their analyses. This study aimed to obtain a water quality index (WQI) to characterize the Mantiqueira Range region. Water quality indicators from a sub-basin entirely occupied by Atlantic Forest and from another predominantly occupied by pasture were normalized and used to compose the WQI. The normalized values were submitted to a PCA evaluation and the WQI was then calculated. The Indicators with greatest weight, according to the PCA, were total coliform, nitrate, fecal coliform, chemical oxygen demand and temperature. The Atlantic forest sub-basin presented the best WQI results, demonstrating the importance of the forested environment in the maintenance of water quality in springs of the Mantiqueira Range region.

The interaction between the surface and groundwater occurs in a dynamic and interconnected way allowing the use of direct and indirect methods for hydro-geological characterization and its contribution to the surface flow. The recession rates and the groundwater flow can be obtained by using the Barnes’ Method. Precipitation is the main component associated with the aquifer recharge process and may also be expressed as a Precipitation Concentration Index (PCI). This work presents recharge data sets based on the separation of the surface hydrograph for the Paraopeba and Sapucaí river basins, in Minas Gerais State. The effect of precipitation on groundwater recharge in the Sapucaí basin is more significant than that of the Paraopeba basin due to predominant land-use and its water and climatic regimes. The contribution of the base flow to total runoff in the Sapucaí basin could exceed 70% in some sub-basins, especially those near the Mantiqueira Range, demonstrating that even in areas with high rainfall concentration the influence of the Atlantic Forest in this process is highly significant.

ABSTRACT The proper design of hydraulic structures depends on estimates of maximum stream flows. The scarce stream flow monitoring in Brazil has led to the use of regionalization methods. The main objective of this study was to develop a tool via regional function to estimate maximum stream flows and their corresponding return periods (RP) with the aid of techniques based on the L-moments method, seeking for adequate hydrologic engineering applications and flood risk management. Annual maximum stream flow historical series were adjusted to traditional 2-parameter probability density functions (PDFs) (Normal, 2-parameter Log-Normal, Gumbel, Gamma) and multiparameter PDFs (GEV and Kappa), based on the L-moments method, which were used in the development of the regional function employing the dimensionless curve method. The regional function’s predictive capability was determined by cross-validation for different RPs. It can be concluded that the approach based on L-moments was successfully used to adjust the regional function. In addition, the regional function: i) was improved when using the aforementioned multiparameter PDFs and ii) was framed as optimum for RP of up to 100 years and considered useful for practical engineering projects and flood risk management.

The spatial characterization of soil attributes is fundamental for the understanding of forest ecosystems. The objective of this work was to develop a geostatistical study of chemical and physical soil attributes at three depths (D1 - 0-20 cm; D2 - 20-50 cm; D3 - 50-100 cm), in an Experimental Hydrographic Micro-catchment entirely covered by Atlantic Forest, in the Mantiqueira Range region, Minas Gerais. All the considered variables presented spatial dependence structure in the three depths, and the largest degrees of spatial dependence were observed for pH in the three depths, soil cation exchange capacity potential in D3, soil organic matter in D1 and D3 and clay and soil bulk density in D2. The method most used for the adjustments of semi-variogram models was the Maximum Likelihood and the most selected model was the Exponential. Furthermore, the ordinary kriging maps allowed good visualization of the spatial distribution of the variables.A caracterização espacial de atributos do solo é fundamental para o entendimento de ecossistemas florestais. Neste trabalho, objetivoi-se desenvolver um estudo geoestatístico de atributos químicos e físicos do solo em três profundidades (P1 - 0-20 cm; P2 - 20-50 cm; P3 - 50-100 cm), em uma Microbacia Hidrográfica Experimental inteiramente coberta por Mata Atlântica, na região Serra da Mantiqueira, Minas Gerais. Todas as variáveis consideradas apresentaram estrutura de dependência espacial nas três profundidades, sendo que os maiores graus de dependência espacial foram observados para pH nas três profundidades, capacidade de troca de cátions potencial do solo em P3, matéria orgânica do solo em P1 e P3 e argila e densidade do solo em P2. O método mais utilizado para ajuste foi o da Máxima Verossimilhança e o modelo mais selecionado foi o Exponencial. Além disso, os mapas de krigagem permitiram boa visualização da distribuição espacial das variáveis.

Estudos associados a chuvas extremas são constituídos de eventos de interesse prático para a gestão dos recursos naturais, como manejo de bacias hidrográficas e conservação dos solos e da água. A distribuição espacial desses eventos possibilita inferir sobre áreas onde sua ocorrência é acentuada e desprovida de informações técnicas. Os objetivos deste trabalho foram promover, a partir de dados pontuais de 177 estações meteorológicas e com a utilização de técnicas geoestatísticas, o mapeamento de chuvas intensas para o Estado de Minas Gerais e identificar as áreas mais vulneráveis no tocante à ocorrência dessas chuvas nesse Estado. Foi constatado que as maiores intensidades ocorrem nas regiões leste e noroeste de Minas Gerais, o que pode ser explicado pela maior influência da Zona de Convergência do Atlântico Sul, além de ocorrência de chuvas convectivas. Foi possível, também, constatar e mapear intensidades intermediárias nas regiões sul e central e os menores valores para as regiões norte e nordeste de Minas Gerais. Para maiores durações, verificou-se, para a região sul, ocorrência de altas intensidades, o que está associado à entrada com maior frequência de frentes frias, produzindo chuvas de longa duração.

The aim of this study was to analyze trends in precipitation and temperature on Trindade Island, South Atlantic Ocean. Time series from 1984 to 2008 for precipitation and from 1958 to 2008 for air temperature were analyzed. The regression analysis and Mann-Kendall test were used to test the trend in annual and seasonal scale of precipitation – January, April, July and October, which represents the middle months of summer, autumn, winter and spring, respectively, as well as for maximum and minimum air temperature. Results indicated that for precipitation time series there was no significant trend, while for minimum air temperature there was a significant trend to decay. In addition, no significant trend was found for maximum air temperature.

O mapeamento da erosividade da chuva e da precipitação pluvial consiste de um instrumento prático e indispensável para o planejamento do uso do solo em escalas regionalizadas, como países, Estados ou grandes bacias hidrográficas. Nesse contexto, objetivou-se neste estudo analisar a continuidade espacial do potencial erosivo da chuva e da precipitação pluviométrica, nas escalas de tempo mensal e anual, e posterior mapeamento destas, para o Estado do Espírito Santo, visando fornecer informações básicas ao planejamento de uso e manejo sustentável do solo. Para isso, 129 estações pluviométricas foram empregadas no estudo; a erosividade da chuva foi calculada tendo-se como base equações de Fournier ajustadas para os Estados vizinhos, porém com características climáticas semelhantes. Observou-se forte estrutura de dependência espacial das variáveis regionalizadas, especialmente da erosividade da chuva, com predomínio do modelo de semivariograma exponencial. Quanto à precipitação pluvial, os valores do grau de dependência espacial foram inferiores aos obtidos para a erosividade; contudo, foi possível classificar a estrutura de dependência como moderada a forte. A região do Rio Doce foi classificada como de "alto" a "muito alto" potencial erosivo, cuja erosividade média anual variou de 7.000 a 11.460 MJ mm ha-1 h-1 ano-1. Nessa região, os solos, além de ocorrerem em relevo dissecado e serem pobres em nutrientes, apresentam déficit hídrico pronunciado, dificultando o estabelecimento da vegetação, e são aqueles de maior vulnerabilidade natural à erosão hídrica.The mapping of rainfall erosivity and rainfall is a practical and indispensable tool to plan the soil and water management on a regional scale, such as countries, states or basins. The purpose of this study was to analyze the spatial continuity of erosive potential of rainfall and rainfall, considering monthly and annual mean values, and to map them for the State of Espírito Santo, Brazil, providing basic information for the planning of sustainable soil use and management. To this end, 129 weather stations were used and monthly values of rainfall erosivity were calculated using Fournier's equations. A strong spatial dependency structure was observed, especially for rainfall erosivity, with data fitting to the exponential semivariogram model. For rainfall, the spatial dependence degree values were slightly lower than for rainfall erosivity, however, a moderate to strong spatial dependence degree was obtained. The rainfall erosivity potential of the Rio Doce region was classified as "strong" and "very strong", varying from 7,000 to 11,460 MJ mm ha-1 h-1 year-1. In this region, the natural vulnerability to water erosion of soils with a dissected relief, low natural fertility and a pronounced water deficit hampering vegetation establishment, is higher.

A proposição de índices de qualidade do solo tem crescido de forma considerável nos últimos anos para análises de sustentabilidade ambiental e da produção agrícola. No entanto, não há, nas condições brasileiras, o desenvolvimento de qualquer indicador de qualidade do solo vinculado à recarga de água subterrânea. O objetivo deste estudo foi gerar um índice de qualidade do solo, relacionado à recarga de água subterrânea (IQS RA), válido para as condições da Bacia Hidrográfica do Alto Rio Grande e proceder a seu mapeamento por meio de técnicas geoestatísticas. O IQS RA proposto é uma combinação linear de três indicadores relacionados à infiltração de água no solo: densidade do solo, condutividade hidráulica saturada e macroporosidade. Para sua validação, foi considerada a participação do deflúvio base (ou subterrâneo) no deflúvio total para quatro sub-bacias da Bacia Hidrográfica do Alto Rio Grande, analisando o comportamento desses indicadores hidrológicos tendo-se como referência a distribuição espacial do IQS RA. O índice gerado mostrou-se uma ferramenta importante para avaliação do potencial do solo para recarga de água subterrânea, uma vez que ele reflete a influência dos usos da terra no comportamento do deflúvio base e, consequentemente, na dinâmica da produção de água pelas sub-bacias.

Rainfall erosivity and its spatial variability were studied for 54 pluviometric stations in Southern Minas Gerais State (48º00' - 44º00'W; 23º50' - 20º00'S), aiming to plan the land-use strategies. Therefore, erosivity factor was determined for the pluviometric stations, using long-term rainfall data sets obtained along with the Brazilian National Water Agency- ANA, which varied from 15 to 40 years. The monthly and annual erosivity indexes were generated using Fournier equation for Lavras, MG and the spatial distribution of rainfall erosivity was studied on the basis of geostatistical approaches considering only the distance which separates them, developing the isotropic experimental semivariogram. The semivariogram adjustment was done based on the Weighted Least Squares method and the spatial dependence degree. Once the structure and the semivariogram adjustment were defined, the ordinary kriging maps were created, providing erosivity spatial behavior in Southern Minas Gerais. It was observed that the Southern Minas Gerais presents high erosivity patterns, ranging from 5,145 to 7,776 MJ mm ha-1 h-1 year-1, in Ijaci (north of region) and Itajubá (southern region), respectively. Besides, it was verified that the erosivity indexes are intensely influenced by the topography, associated with climatic conditions. Higher erosivity is connected to areas with a higher altitude, such as along the Mantiqueira Range Mountain, and on high plateaus and mountain ranges in the North-Central part of the region. The geostatistical approach using long-term rainfall data in Southern region of Minas Gerais state, which is a relatively heterogeneous region in terms of altitude, soil depth and slope, showed to be adequate to the proposal of this study.Foram estudadas a erosividade e sua variabilidade espacial para cinquenta e quatro estações pluviométricas do Sul de Minas Gerais (48º00' - 44º00'W; 23º50' - 20º00'S) visando à implementação do planejamento do uso local da terra. Para tanto, determinou-se o fator erosividade para séries de precipitação pluviométrica, utilizando dados de precipitações obtidas junto à Agencia Nacional de Água - ANA, constituindo-se séries históricas que variaram de 15 a 40 anos. Os índices de erosividade mensais e anuais foram obtidos, utilizando a equação de Fournier utilizada em Lavras, MG e a variabilidade espacial da erosividade foi realizada com base nos princípios da geoestatística, considerando-se apenas a distância que os separa, construindo-se o semivariograma experimental isotrópico. O ajuste do semivariograma foi realizado com base no método dos Mínimos Quadrados Ponderados e no grau de dependência espacial. Definida a estrutura e o ajuste do semivariograma passou-se à fase de geração dos mapas de krigagem, gerando o comportamento espacial das erosividades, na região Sul de Minas Gerais. Observou-se que a região Sul de Minas Gerais apresenta elevados padrões de erosividade, com amplitude de 5.145 a 7.776 MJ mm ha-1 h-1 ano-1, para Ijaci (região norte) e Itajubá (região sul), respectivamente. Os índices de erosividade da região do Sul de Minas Gerais foram considerados elevados e com forte influência da topografia, associados às características climáticas. Maiores erosividades estão associadas às áreas de maior altitude, como ao longo da Serra da Mantiqueira e em planaltos e serras elevadas no centro-norte da região. A abordagem geoestatística com dados de longo prazo de chuva para a região Sul de Minas Gerais, que é uma região relativamente heterogênea em termos de altitude, profundidade do solo e declive, mostrou-se adequada à proposta do presente estudo.

http://dx.doi.org/10.5902/198050986621Os objetivos deste estudo foram verificar a possibilidade do uso da estrutura de dependência espacial para a definição de estratos em povoamentos florestais e comparar, com base no erro de amostragem, a Amostragem Casual Simples (ACS) e a Amostragem Casual Estratificada (ACE), sendo a estratificação realizada por meio dos interpoladores espaciais Inverso do Quadrado da Distância (IQD) e Krigagem. Os dados utilizados foram provenientes de inventários convencionais realizados nos anos de 2006 e 2007, em projetos localizados nos municípios de Curvelo, João Pinheiro e Montes Claros, Minas Gerais. Os resultados mostraram que, dos 50 projetos, 64 % apresentaram grau de dependência espacial de médio a forte, evidenciando que o uso de métodos geoestatísticos possibilita redução no erro sem aumento de custo no inventário. A estratificação com base no interpolador IQD utilizada nos projetos que apresentaram fraco grau de dependência espacial (DE) contribuiu para uma redução em média de 68,4 % no erro de amostragem. A utilização do interpolador geoestatístico nos projetos que apresentaram de média a forte DE, contribuiu para uma redução média de 47,0 % e 65,7 % no erro de amostragem, respectivamente. Mesmo nos projetos onde a estrutura de dependência espacial se manifestou, a estratificação com base no interpolador IQD gera melhoria das estimativas da ACE em relação à ACS.

Pedology consists of a sub-area of Soil Science that studies the soil and its origin as well as its inter-relationship with the landscape. Hydrology is the science that studies the water in nature in its different mediums (atmosphere, soil and rock), using the watershed as a reference for analysis of the water dynamics and also its interaction with the landscape. The relationship between these two branches of knowledge has been the object of debate and analysis in recent years, contributing to the creation of a multidisciplinary science, which seeks to integrate the respective fields of research. As such, for Hydrology, Pedology has been fundamental for enabling a foundation for the processes associated to the generation of runoff and groundwater recharge, especially concerning the micro-morphological analysis of the soil and the horizons which may impede the water flow, and their relationships with the soil structure. For Pedology, Hydrology can be fundamental to the understanding of the soil formation processes in the different landscapes, in the context of materials deposition as well as the shaping of the relief, as consequence of the soil-climate-drainage interaction, and its importance for pedogenesis. Therefore, the understanding and the deepening of the pedologic analyses, on a microscale and in toposequence in a specific landscape, and its insertion in the theories of Hydrology will allow the development of more realistic, physically based hydrological models and less parameterization dependence, this now being one of the most important challenges for the hydrologist.A Pedologia consiste de uma subárea da Ciência do Solo que estuda o solo e sua origem bem como sua relação com a paisagem. A Hidrologia é a ciência que estuda a água na natureza nos seus diferentes meios (atmosfera, solo e rocha), utilizando a bacia hidrográfica como referência para análise da dinâmica da água e sua interação com a paisagem. A relação entre esses dois ramos do conhecimento tem sido objeto de debate e análise nos anos recentes, contribuindo para a criação de uma ciência multidisciplinar, a qual busca interagir os respectivos campos de pesquisa. Assim, para a Hidrologia, a Pedologia tem sido fundamental por possibilitar um embasamento sobre os processos associados à geração do escoamento e recarga subterrânea, especialmente no tocante à análise micromorfológica do solo e aos horizontes ou camadas subsuperficiais de impedimento ao fluxo de água e suas relações com a estrutura do solo. Para a Pedologia, a Hidrologia pode ser fundamental no entendimento dos processos de formação dos solos, nas diferentes paisagens, tanto no contexto de deposição de material quanto da conformação do relevo, fruto da interação solo-clima-escoamento, e sua importância para a pedogênese. Assim, o entendimento e o aprofundamento das análises pedológicas, em microescala e em topossequência, numa determinada paisagem, e sua inserção nos fundamentos e teorias da Hidrologia permitirão o desenvolvimento de modelos hidrológicos mais realísticos e embasados fisicamente, e menos dependentes de parametrização, sendo este um dos desafios mais importantes para o hidrólogo atualmente.

Relationships between regional climates and oceanic and atmospheric anomalies are important in understanding the rainfall regime of a given region. This work aimed to analyze rainfall erosivity in the Upper Grande River Basin, Southern Minas Gerais State, Brazil; namely the two most representative environments, the Mantiqueira Range (MR) and the Plateau of Campos das Vertentes (PCV). These areas can be affected by the El Niño Southern Oscillation (ENSO) phenomena, which can be evaluated by indicators such as Sea Surface Temperature (SST) for the Niño 3.4 Region. Rainfall erosivity was calculated for individual rainfall events from January, 2006 to December, 2010. Pearson's coefficient of correlation was used to evaluate the relationships between rainfall variables and SST. The coefficients of correlation were significant for both sub-regions. Correlations between the rainfall variables and negative oscillations of SST were also significant, especially in the MR sub-region, however, the Person's coefficients were lower than those obtained for the SST positive oscillations. These results demonstrate that El-Niño phenomenon can be considered an important factor in the intense rainfall behavior of the Upper Grande River Basin.Relações entre o clima regional e as anomalias oceânicas e atmosféricas consistem de importantes ferramentas para o entendimento do regime de chuvas intensas em uma dada região. Neste trabalho, objetivou-se analisar a erosividade da chuva na bacia hidrográfica do Alto Rio Grande, sul de Minas Gerais. O estudo considerou as duas sub-regiões mais representativas da mesma, sendo a Serra da Mantiqueira (SM) e o Planalto Campos das Vertentes (PCV). Essas áreas podem ser afetadas pelos fenômenos associados ao El Niño Oscilação Sul (ENSO), o qual pode ser avaliado como função da Temperatura da Superfície do Mar (TSM) para a região do Niño 3.4. A erosividade da chuva foi calculada para cada evento individual de chuva entre janeiro/2006 e dezembro/2010. O coeficiente de correlação de Pearson foi usado para avaliar as possíveis relações entre as variáveis associadas às chuvas erosivas e à TSM. Os coeficientes de correlação foram significativos para ambas as sub-regiões. As correlações entre as variáveis estudadas e as oscilações negativas da TSM também foram significativas, especialmente para a sub-região SM, contudo, os coeficientes foram menores do que aqueles obtidos para oscilações positivas. Os resultados demonstram que o fenômeno El-Niño pode ser mais importante para o comportamento de chuvas intensas na cabeceira da bacia do rio Grande.

A distribuição espacial da condutividade hidráulica saturada (k0) é essencial para estudos relacionados a erosão do solo e escoamento superficial. Este trabalho objetivou estudar a continuidade espacial do atributo hidrológico do solo k o na Bacia Hidrográfica do Alto Rio Grande, MG, e realizar seu mapeamento por meio de técnicas geoestatísticas, utilizando dados sem e com transformação logarítmica. Os modelos de semivariograma esférico e exponencial foram ajustados ao semivariograma experimental pelo método dos Mínimos Quadrados Ordinários (MQO) e Mínimos Quadrados Ponderados (MQP). Técnicas de validação cruzada e preditiva foram aplicadas para a escolha do melhor modelo. Os resultados indicaram que, ao se trabalhar com o logaritmo dos dados de k o, houve redução de pontos discrepantes e de anisotropia, entretanto os valores mais elevados de grau de dependência espacial foram observados nos dados sem transformação. O ajuste do modelo esférico, por meio do método MQO, foi o que produziu melhor desempenho na modelagem da continuidade espacial de k0. Os mapas gerados a partir dos dados sem e com transformação logarítmica não apresentaram o mesmo comportamento na distribuição espacial dos valores, e o mapa dos dados na forma transformada teve o melhor detalhamento da distribuição espacial.