ABSTRACT Alternative methods to the intensity-duration-frequency equations have been used for intense rainfall study in places with no pluviographic data. A pioneering study, by CETESB (1986), established rainfall disaggregation coefficients for Brazil; however, the use of these coefficients take into account neither the rainfall characteristics of the interest locality nor the return period influence in obtaining the precipitation intensities. This study aimed to determine rainfall disaggregation coefficients for Doce river basin; to verify the validity of the regional coefficients use for the entire basin; and to evaluate the return period influence on these coefficients. Data from 19 gauges located in the basin, with rainfall associated with durations of 10 to 1440 min and return periods of 2, 5, 10, 20, 50 and 100 years, were used to obtain the coefficients. Student's t-test was used to assess the regional applicability of these coefficients and the return period influence. The coefficients do not provide regional validity for the entire basin; therefore, regional coefficients were estimated for five hydrologically homogeneous regions, confirming the validity of these coefficients use and the influence of the return period. We conclude that the disaggregation coefficients must be specific for the homogeneous regions and for each return period.

ABSTRACT Detecting trends in streamflow and rainfall series can have great significance for proper water resource management. Thus, the objective of this study was to analyze the trends of historical streamflow and rainfall series using nonparametric statistical tests. A historical series of pluviometric and fluviometric gauges, which belong to the hydrometeorological network of the Brazilian Water National Agency in the Santo Antônio River Basin, Brazil, from 1985 to 2014 were used. By applying statistical tests, it was found that the time series are independent and random, and from the total 24 rainfall gauges evaluated, 12 presented nonstationary behavior, exhibiting mostly decreasing trends. Based on the six fluviometric gauges used for the annual streamflow series, only the annual data of one gauge tended to decrease to the minimum streamflow. However, for the monthly series, three gauges showed decreasing trends between July and September. This decrease in streamflow may be a consequence of rainfall reductions, high water demand, and changes in land use and cover.

ABSTRACT This study aimed to use global sensitivity analysis (GSA) methods to evaluate the sensitivity of the SAC-SMA hydrologic model parameters in the estimation of daily flows of the Piracicaba river basin. The study was carried out in three sections of flow monitoring of the Piracicaba river basin, with an area of 5,304.0 km2 and located in the State of Minas Gerais, Brazil. For the global sensitivity analysis of the SAC-SMA model, the Morris and Sobol methods were used. The model parameters showing high sensitivity were UZFWM, which represents the free water depth in the upper zone of the soil and interferes with the subsurface flow and groundwater aquifer recharge; ADIMP, which represents the additional impermeable area of the basin and interferes with the direct runoff generation; and LZPK, LZSK, LZFPM, and LZFSM, which are related to the base flow of the basin. The results showed that most of the SAC-SMA model parameters do not provide expressive variations in the output variable, most of the SAC-SMA model parameters with high sensitivity are the intervenient in the base flow, and the Morris method should be used as a preliminary analysis to the use of the Sobol method.

Abstract: The environmental fragility analysis evaluates the susceptibility of an environment to degradation. Thus, the goals of this work are to analyze and map the environmental fragility of the Lapa Grande State Park (PELG), Brazil, and its buffer zone (ZA) and also quantify the changes in the vegetation cover before and after the implementation of the PELG. The environmental fragility was evaluated through multicriteria analysis using the factors: slope, geology, pedology and land use and land cover. The changes in the high vigor vegetation cover were determined from the normalized difference vegetation index (NDVI) for 1996, 2006 and 2016. It was verified that the central-east and northeast regions of the PELG presented the greatest environmental fragilities in 1996, and significant reductions in the areas with high and very high fragility were observed in 2006 and 2016 due to the increase in the vegetation cover after the implementation of the PELG, which was more expressive in the park area than in the ZA. The increase of 20.7% of 2006 to 2016 in the vegetation with greater vigor, proved the importance of the creation of a conservation unit.

Abstract: In order to characterize the occurrence and intensity of droughts in the Doce River Basin, as well as to develop a system for its classification, four different drought indexes were evaluated: Percent of Normal Precipitation (PNP), Deciles Method (DM), Rainfall Anomaly Index (RAI) and Standardized Precipitation Index (SPI). The indices were calculated annually, based on precipitation data from 89 rainfall stations of the Brazilian National Water Agency (ANA). Nine analysis units (AUs) were determined in the basin and the Thiessen Polygons method was used to obtain the average precipitation in the respective drainage areas. The indices were calculated for each AU and then related to the drought intensity classes. An overall classification of the indices was proposed for the drought classification system for a 30-year base period, from 1985 to 2015. The most critical hydrological years of the Doce River Basin in relation to the drought were 1994/1995, 2000/2001 and 2014/2015, the latter being the most critical of the last 30 years. The results show that the annual drought classification system proved to be efficient in the identification of events, allowing to verify that the Doce River Basin presents a severe climatic drought condition, on average, every seven years.

ABSTRACT Evaporation rates in reservoirs influence the volume of water available for multiple uses. Thus, the objective of this study was to estimate the evaporation rates and the evaporated volumes per unit time in the Tucuruí-PA and Lajeado-TO reservoirs based on the methods in Linacre (1993), Kohler et al. (1955), Morton (1983), Bruin & Keijman (1979) and Penman (1948) method was adopted as the standard. The mean annual evaporation rates in the Tucuruí and Lajeado reservoirs, estimated by the Penman method, were similar, with values of 1,784 mm and 1,882 mm, respectively. None of the alternative analyzed methods could be used to estimate the mean annual evaporation in the Tucuruí and Lajeado reservoirs and could not replace the Penman method. However, the Linacre (1993) and Bruin & Keijman (1979) methods could be used to estimate monthly evaporation during the dry season in Tucuruí. The mean evaporated volume per unit time and the mean net evaporated volume per unit time in the Tucuruí reservoir correspond to 120% and 50%, respectively, of the total water demand in the Tocantins-Araguaia region, while the mean evaporated volume per unit time and the mean net evaporated volume per unit time in the Lajeado reservoir correspond to 120% and 50%, respectively, of the total water demand in the basin.

ABSTRACT This study aimed at testing the fit of continuous probability distributions to a daily reference evapotranspiration dataset (ET0) at a 75% probability level for designing of irrigation systems. Reference evapotranspiration was estimated by the Penman-Monteith method (FAO-56-PM) for eight locations, within the state of Espírito Santo (Brazil), where there are automatic gauge stations. The assessed probability distributions were beta, gamma, generalized extreme value (GEV), generalized logistic (GLO), generalized normal (GN), Gumbel (G), normal (N), Pearson type 3 (P3), Weibull (W), two- and three-parameter lognormal (LN2 and LN3). The fitting of the probability distributions to the ET0 daily dataset was checked by the Kolmogorov-Smirnov's test. Among the studied distributions, GN was the only one to fit the ET0 data for all studied months and locations. We should also infer that continuous probability models have a good fit to the studied ET0 dataset, enabling its estimation at 75% probability through a Generalized Normal distribution (GN). Therefore, it can be used for the sizing of irrigation systems according to a given degree of risk.

ABSTRACT The objective of this study was to compare ecohydrological simulations from a one-dimensional model (PHABSIM - Physical Habitat Simulation System) and a two-dimensional model (River2D) in order to indicate a reliable tool that could be used to determine public policies for the sustainable management of the water resources of the FormosoRiver basin(MG). The results from the calibration of hydraulic variables, namely, water depth and velocity, as well as habitat predictions for three fish species of the river were compared. The results showed that River 2D was best suited to simulate ecohydrological features for the studied river stretch. Although PHABSIM presented a better fit of the hydraulic variables at the calibration process, the use of only three monitoring cross sections to compose the biotic model database compromised its habitat modeling. PHABSIM model was not able to accurately assess the actual characteristics of the physical habitat in the segments of the river located between the monitoring cross sections.

ABSTRACT Accurate studies on reservoir evaporations are important for proper management of water resources. Therefore, this study aimed to compare evaporation estimates for Três Marias and Sobradinho reservoirs made by Linacre, Kohler et al., Thornthwaite, Complementary Relationship Lake Evaporation (CRLE) and A class pan method, which was calculated by the Penman method. We also compared evaporation values from weather stations located within areas of the reservoirs against data from stations located near the reservoir areas. Our results showed that the Linacre model overestimated evaporation for both reservoirs compared to the Penman method. However, Kohler et al. and Thornthwaite underestimated the evaporation for both areas. Evaporation estimates near those obtained by the Penman model were found for the class A pan model in Sobradinho reservoir, using a kp of 0.6. Moreover, in Três Marias, the Penman and CRLE models had statistically equal evaporation estimates. The estimates calculated from data of meteorological stations within reservoir areas were statically different from those obtained using data of stations near them.

RESUMO Estudos que possibilitem a obtenção de estimativas precisas de evaporação em reservatórios representam uma importante ação para o adequado gerenciamento e manejo dos recursos hídricos. Dessa forma, objetivou-se comparar as estimativas de evaporação, dos reservatórios de Três Marias e Sobradinho, calculadas pelos modelos de Linacre et al. (1993), Kohler et al. (1995), Thornthwaite (1948), CRLE e o método do tanque Classe A com o valor estimado pelo modelo de Penman et al. (1948). Também foram comparados os valores de evaporação estimados a partir de dados de estações meteorológicas situadas no entorno do reservatório com o valor estimado com dados da estação localizada na área da barragem. Os resultados permitiram constatar que, em relação ao modelo de Penman et al. (1948), o modelo Linacre et al. (1993), superestima a evaporação nos reservatórios de Sobradinho e Três Marias e os modelos Kohler et al. (1955) e Thornthwaite (1948) subestimam a evaporação nos dois reservatórios. O método que proporcionou resultados mais próximos daqueles obtidos por Penman et al. (1948), no reservatório de Sobradinho, foi o do tanque Classe A, utilizando o coeficiente de 0,6; já em Três Marias, foram os modelos Penman et al. (1948) e CRLE, que apresentaram resultados de evaporação estatisticamente iguais. Os valores de evaporação estimados pelas estações meteorológicas ao entorno dos reservatórios não são estatisticamente iguais aos estimados pelas estações localizadas na área da barragem.

ABSTRACT This study aimed to develop a methodology based on multivariate statistical analysis of principal components and cluster analysis, in order to identify the most representative variables in studies of minimum streamflow regionalization, and to optimize the identification of the hydrologically homogeneous regions for the Doce river basin. Ten variables were used, referring to the river basin climatic and morphometric characteristics. These variables were individualized for each of the 61 gauging stations. Three dependent variables that are indicative of minimum streamflow (Q7,10, Q90 and Q95). And seven independent variables that concern to climatic and morphometric characteristics of the basin (total annual rainfall – Pa; total semiannual rainfall of the dry and of the rainy season – Pss and Psc; watershed drainage area – Ad; length of the main river – Lp; total length of the rivers – Lt; and average watershed slope – SL). The results of the principal component analysis pointed out that the variable SL was the least representative for the study, and so it was discarded. The most representative independent variables were Ad and Psc. The best divisions of hydrologically homogeneous regions for the three studied flow characteristics were obtained using the Mahalanobis similarity matrix and the complete linkage clustering method. The cluster analysis enabled the identification of four hydrologically homogeneous regions in the Doce river basin.

RESUMO Este trabalho teve por objetivo propor uma metodologia baseada em análises estatísticas multivariadas de componentes principais e de agrupamento, com o intuito de identificar as variáveis mais representativas em estudos de regionalização de vazões mínimas e otimizar a obtenção das regiões hidrologicamente homogêneas para a bacia hidrográfica do Rio Doce. Foram utilizadas 10 variáveis referentes às características climáticas e morfométricas da bacia. Essas variáveis foram individualizadas para as 61 estações fluviométricas adotadas, sendo três variáveis dependentes e indicativas das vazões mínimas (Q7,10, Q90 e Q95) e sete independentes (precipitação total anual – Pa; precipitação total do semestre seco – Pss e chuvoso –Psc; área de drenagem da bacia –Ad; comprimento do rio principal –Lp; comprimento total dos cursos d'água da bacia – Lt; e declividade média da bacia –SL). O resultado da análise de componentes principais apontou a variável independente SL como a menos representativa e foi excluída do estudo. As variáveis independentes mais representativas foram Ad e Psc. As melhores divisões de regiões hidrologicamente homogêneas para as três vazões características estudadas foram obtidas utilizando-se conjuntamente da matriz de similaridade de Mahalanobis e do método de agrupamento do vizinho mais distante. A análise de agrupamento possibilitou a identificação de quatro regiões hidrologicamente homogêneas na bacia hidrográfica do Rio Doce.

This paper presents the second part of the methodology developed to project hydrometric networks of quantitative monitoring of watersheds, emphasizing exclusion, inclusion and rearrangement of monitoring stations. The presented methodology has as study area the Doce River Basin (DRB) and it is based on spatial analysis of maps generated by kriging for regionalized variables: minimum specific flow of 7 days duration and return period of 10 years - q7,10 and precipitation of dry season - Pss. Applying the methodology developed for the DRB, it was concluded that there were significant improvements in the standard deviations of estimates of flow for 6 of the 9 ottobacias, culminating with the rearrangement of 18 stations and excluding 2 stations in the gauging monitoring network. It was also observed that there were improvements too in the estimates of spatialized precipitation enabling the spatial rearrangement of 12 stations. It is noteworthy, however, the need for inclusion of 67 stations in the network monitoring rainfall. The methodology was adequate for the proposed objective and can be applied to any watershed.

Este artigo apresenta a segunda parte da metodologia desenvolvida para projeto de redes hidrométricas de monitoramento quantitativo em bacias hidrográficas, com ênfase na exclusão, rearranjo e inclusão de estações de monitoramento. A proposta metodológica apresentada tem, como área de estudo, a Bacia Hidrográfica do Rio Doce (BHRD) e se baseia na análise espacial dos mapas gerados pela krigagem para as variáveis regionalizadas: vazão específica mínima com 7 dias de duração e período de retorno de 10 anos (q7,10) e precipitação do semestre mais seco (Pss). Aplicando-se a metodologia desenvolvida para a BHRD, verificaram-se melhorias significativas nos desvios padrão percentuais das estimativas de vazão para seis das nove ottobacias estudadas, culminando com o rearranjo de 18 estações e exclusão de duas estações na rede de monitoramento fluviométrico. Verificou-se, ainda, que houve melhorias nas estimativas espacializadas de precipitação com o rearranjo espacial de 12 estações porém se destaca a necessidade de inclusão de 67 estações na rede de monitoramento pluviométrico. A metodologia mostrou-se adequada para o objetivo proposto podendo ser aplicada a qualquer bacia hidrográfica.

In this study, the implementation of the first part of the proposed methodolgy for hydrometric network design aimed to the unbiased spatialization of hydrometric data of fluviometric and rainfall networks existing in the Doce river basin (DRB), from the descriptive statistical analysis and geostatistical analysis. Average minimum specific flow of seven consecutive days and return period of 10 years - q7,10 and total precipitation of half dry - Pss variables were used in this study. Applying the developed methodology it was observed that the values of q7,10 in DRB, in general, decrease from west to east, ranging from 0.51 to 8.47 L s-1 km-2. The variable Pss showed higher values in the region of the head waters and low course of DRB and minimum values in the central region, ranging from 147 to 243 mm. The proposed methodology allow a unbiased spatialization of study variables in DRB, allowing to estimate data in areas not monitored with lower uncertainty.

Neste estudo a aplicação da primeira parte da proposta metodológica para projeto de redes hidrométricas teve, por objetivo, a espacialização não tendenciosa dos dados hidrométricos das redes fluviométrica e pluviométrica existentes na bacia hidrográfica do rio Doce (BHRD) a partir da análise estatística descritiva e da análise geoestatística. Utilizaram-se, neste estudo, as variáveis vazão específica mínima média de sete dias consecutivos e período de retorno de 10 anos (q7,10) além da precipitação total do semestre mais seco (Pss). Observou-se, aplicando a metodologia desenvolvida que, de forma geral, os valores de q7,10 na BHRD diminuem de oeste para leste com variação de 0,51 a 8,47 L s-1 km-2 enquanto a variável Pss apresentou maiores valores na região de cabeceira do rio Piranga e no baixo Doce e valores mínimos na região central da bacia com variação de 147 a 243 mm. A aplicação da metodologia proposta permitiu a espacialização não tendenciosa das variáveis em estudo na BHRD, possibilitando estimar dados em regiões não monitoradas e com menor incerteza.

Hydrological models are important tools that have been used in water resource planning and management. Thus, the aim of this work was to calibrate and validate in a daily time scale, the SWAT model (Soil and Water Assessment Tool) to the watershed of the Galo creek , located in Espírito Santo State. To conduct the study we used georeferenced maps of relief, soil type and use, in addition to historical daily time series of basin climate and flow. In modeling were used time series corresponding to the periods Jan 1, 1995 to Dec 31, 2000 and Jan 1, 2001 to Dec 20, 2003 for calibration and validation, respectively. Model performance evaluation was done using the Nash-Sutcliffe coefficient (E NS) and the percentage of bias (P BIAS). SWAT evaluation was also done in the simulation of the following hydrological variables: maximum and minimum annual daily flowsand minimum reference flows, Q90 and Q95, based on mean absolute error. E NS and P BIAS were, respectively, 0.65 and 7.2% and 0.70 and 14.1%, for calibration and validation, indicating a satisfactory performance for the model. SWAT adequately simulated minimum annual daily flow and the reference flows, Q90 and Q95; it was not suitable in the simulation of maximum annual daily flows.

Os modelos hidrológicos são ferramentas importantes que vêm sendo utilizadas no planejamento e na gestão dos recursos hídricos. Assim, objetivou-se com este trabalho calibrar e validar, numa escala de tempo diária, o modelo SWAT (Soil and Water Assesment Tool) para a bacia hidrográfica do Córrego do Galo, situada no Estado do Espírito Santo. Para a realização do estudo foram utilizados mapas georreferenciados de relevo, tipo e uso do solo, além de séries históricas diárias de clima e vazão da bacia. Na modelagem foram utilizadas séries temporais correspondentes aos períodos de 1º-1- 1995 a 31-12-2000 e 1º-1-2001 a 20-12-2013, para a calibração e validação, respectivamente. A avaliação do desempenho do modelo foi realizada usando os coeficientes de Nash-Sutcliffe (E NS) e percentual de viés (P BIAS). Também foram feitas avaliações do SWAT na simulação das seguintes variáveis hidrológicas: vazões máximas e mínimas diárias anuais; e vazões mínimas de referência Q90 e Q95, com base no erro médio absoluto. Os valores de E NS e P BIAS foram de 0,65 e 7.2% e 0,70 e 14.1%, na calibração e na validação, respectivamente, indicando desempenho satisfatório do modelo. O SWAT simulou adequadamente as vazões mínimas diárias anuais e as de referência para outorga Q90 e Q95 e não foi adequado na simulação das vazões máximas diárias anuais.

The edafoclimatic conditions of the Brazilian semiarid region favor the water loss by surface runoff. The state of Ceará, almost completely covered by semiarid, has developed public policies for the construction of dams in order to attend the varied water demand. Several hydrological models were developed to support decisive processes in the complex management of reservoirs. This study aimed to establish a methodology for obtaining a georeferenced database suitable for use as input data in hydrological modeling in the semiarid of Ceará. It was used images of Landsat satellite and SRTM Mission, and soil maps of the state of Ceará. The Landsat images allowed the determination of the land cover and the SRTM Mission images, the automatic delineation of hydrographic basins. The soil type was obtained through the soil map. The database was obtained for Jaguaribe River hydrographic basin, in the state of Ceará, and is applicable to hydrological modeling based on the Curve Number method for estimating the surface runoff.

As condições edafoclimáticas do semiárido brasileiro favorecem a perda de água por escoamento superficial. O Estado do Ceará,quase totalmente abrangido pelo semiárido, desenvolveu políticas públicas voltadas para a construção de açudes,a fim de atender à demanda hídrica diversificada. Vários modelos hidrológicos foram desenvolvidos para subsidiar os processos decisórios no complexo manejo dos reservatórios. Este trabalho teve como objetivo estabelecer uma metodologia para a obtenção de uma base de dados georreferenciada e adequada para uso como dados de entrada na modelagem hidrológica,no semiárido cearense. Foram utilizadas imagens de satélite Landsat e da missão SRTM, e mapa de solos do Estado do Ceará. As imagens Landsat possibilitaram determinar a cobertura do solo,e as imagens da missão SRTM, a delimitação automática das bacias hidrográficas. O tipo de solo foi obtido por meio do mapa de solos. A base de dados foi obtida para a bacia hidrográfica do Rio Jaguaribe, Ceará, e é aplicável à modelagem hidrológica com base no método do Número da Curva para a estimativa do escoamento superficial.

The state of Ceará, Brazil, has 75% of its area covered by Brazilian semiarid, with its peculiar features. In this state, the dams are constituted in water structure of strategic importance, ensuring, both in time and space, the development and supply of water to population. However, construction of reservoirs results in various impacts that should be carefully observed when deciding on their implementation. One of the impacts identified as negative is the increased evaporation, which constitutes a major component of water balance in reservoirs, especially in arid regions. Several methods for estimating evaporation have been proposed over time, many of them deriving from the Penman equation. This study evaluated six different methods for estimating evaporation in order to determine the most suitable for use in hydrological models for water balance in reservoirs in the state of Ceará. The tested methods were proposed by Penman, Kohler-Nordenson-Fox, Priestley-Taylor, deBruim-Keijman, Brutsaert-Stricker and deBruim. The methods presented good performance when tested for water balance during the dry season, and the Priestley-Taylor was the most appropriate, since the data from de simulated water balance with evaporation estimated by this method were the closest of the water balance data observed from measures of reservoir level and the elevation-volume curve provided by the Company of Management of Water Resources of the state of Ceará - COGERH.

O Estado do Ceará possui 75% do território abrangido pelo semiárido brasileiro, com suas características peculiares. Nesse Estado, açudes constituem-se em estrutura hídrica de importância estratégica, garantindo, no tempo e no espaço, o desenvolvimento e o abastecimento hídrico das populações. No entanto, a construção de reservatórios implica vários impactos que devem ser cuidadosamente observados no momento de decidir pela sua execução. Um dos impactos apontados como negativo é o aumento da evaporação, que se constitui em um dos principais componentes do balanço hídrico nos reservatórios, sobretudo em regiões áridas. Vários métodos de estimativa da evaporação foram propostos ao longo do tempo, muitos deles derivados da equação de Penman. Neste trabalho, foram avaliados seis diferentes métodos de estimativa da evaporação a fim de determinar qual o mais adequado para utilização em modelos hidrológicos para o balanço hídrico em reservatórios no Estado do Ceará. Os métodos avaliados foram os propostos por Penman, Kohler-Nordenson-Fox, Priestley-Taylor, deBruim-Keijman, Brutsaert-Stricker e deBruim, os quais apresentaram ótimo desempenho quando testados para o balanço hídrico durante a estação seca, sendo o de Priestley-Taylor o mais adequado, uma vez que os dados do balanço hídrico simulado com a componente evaporação estimada por este método foram os mais próximos dos dados do balanço hídrico observado a partir das medidas de nível do reservatório e da curva cota-volume fornecidos pela Companhia de Gestão dos Recursos Hídricos do Estado do Ceará - COGERH.