Fernando Falco Pruski

Hydrological simulation using SWAT model in headwater basin in Southeast Brazil

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 Espirito 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 (ENS) and the percentage of bias (PBIAS). 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. ENS and PBIAS 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.

NetErosividade MG: erosividade da chuva em Minas Gerais

Rainfall erosivity represents the potential of rainfall causing soil erosion. This study aimed to develop a software to estimate rainfall erosivity in the state of Minas Gerais based on Artificial Neural Networks (ANNs). The annual value of the rainfall erosivity is given by the sum of the monthly values of the erosivity indexes EI30 or KE > 25. Two methodologies were used to estimate the kinetic energy for each index. Thus, four erosivity values were evaluated for each month, resulting in the development of 48 ANNs. These ANNs were implemented using the software Borland Delphi 7.0. The new software was called NetErosividade MG. The program calculates the monthly and annual values of rainfall erosivity for any location in the state of Minas Gerais in an easy and fast way.

Modeling of water infiltration in soil under stratified conditions using the Green-Ampt equation

Soil water infiltration is one of the most important processes of the hydrological cycle. The Green and Ampt equation (GA) is quite used to simulate the infiltration process, however, several authors showed the necessity of some adaptations in the GA parameters: saturation moisture (qs), hydraulic conductivity (K0) and mean suction in the wetting front (y). An evaluation was made of the GA model and of the several correction propositions of K0 and y, applied in a stratified Red-Yellow Latosol. A soil box filled with soil material belonging to three horizons of the studied soil was used. The accumulated infiltration (I), infiltration rate (Ti), as well as the physical characteristics of the profile needed for the application of the model were determined. Simulations based on the combination among six methodologies for the determination of y was made and three for the determination of hydraulic conductivity in the transmission zone (Kw). The following combinations simulated well the infiltration process: Kw equal to 0,5 K0 associated to y relative to the initial moisture content (y(qi)); Kw equals to the stable infiltration rate (Tie) associated to y equal to the mean among y (qi) and y relative to the saturation field moisture (y (qw)); Kw equal to K0 associated to y calculated with base in the texture and porosity of the soil and Kw equal to Tie associated to y calculated on the basis of texture and porosity of the soil.

Validação do modelo ClimaBR em relação ao número de dias chuvosos e à precipitação total diária

This study was accomplished with the objective of validate the ClimaBR model in what refers to generate synthetic series of total daily rainfall in different Brazilian places. For that, synthetic series of rainfall were generated for 12 places, chosen in a distributed way, so that all the different homogeneous rainfall Brazilians regions were observed. Starting from the pluviometric series, available in the meteorological stations from selected places, the ClimaBR was used to generate the synthetic series of rainfall; it was generated 100-year-old series to each place. The results quality was analyzed comparing the adjustment among the observed values and the generated values by ClimaBR, through simple lineal regression and of other statistical indicators. The results obtained allow affirming that, in agreement with the conditions considered in the present study, the software ClimaBR presented good acting to generate of synthetic series of precipitation (number of wet days and daily total rainfall) for all of the tested places.

Substituição dos parâmetros do modelo de Green-Ampt-Mein-Larson para estimativa da infiltração em alguns solos do Brasil

Based on a detailed analysis of the process of water infiltration into the soil, an alternative is proposed to adjust the input parameters of the Green-Ampt-Mein-Larson (GAML) model to optimize infiltration estimates of some Brazilian soils. The adjustments consisted of the replacement of the parameters saturated hydraulic conductivity (K0) by stable infiltration rate (Tie) and soil moisture saturation (qs) by water content in the transmission zone (qw). Moreover, an equation was established to estimate the matric potencial at the wetting front (yf), based on the parameters of the water retention curve of Brooks and Corey. The performance of the set of proposed adjustments (GAML-t) was evaluated for the estimation of water infiltration in three soil types. The performance of GAML-t was compared with the original GAML and adjusted to five different situations. GAML-t performed best in the three soils under study.

Comparação de produtos de precipitação para a América do Sul

COMPARISON OF PRECIPITATION PRODUCTS FOR SOUTH AMERICA This work compares five precipitation datasets for South America, for the period 2000-2004, considering the meridional variation, the variation across the main continental watersheds (Amazonas, Tocantins, Sao Francisco, Orinoco, Parana/Prata, in addition to the main Patagonia basins) and across the main vegetation types (tropical evergreen forest, tropical deciduous forest, woodland, savanna and grassland/steppe). We compare three products based on a combination of rain gauge measurements and satellite data (TRMM, CMAP and GPCP) and two based on reanalyzed meteorological datasets (NCEP/NCAR and CPTEC). The results indicate that the annual average precipitation fields of the different products present different behavior among them. For example, the CPTEC reanalysis does not represent the main regimes of precipitation in the continent, overestimating the precipitation in the interior of northeast Brazil and underestimating the precipitation in the rest of the continent. The combined rain gauge-remote sensing products obtained similar patterns, mainly CMAP and GPCP.

Efeito das mudanças climáticas na disponibilidade hídrica da bacia hidrográfica do Rio Paracatu

The increase of water use in the Paracatu basin is leading to deep environmental problems and conflicts among the users. For a more efficient water resources management, the knowledge of the basins hydrologic behavior is important, in the present and in the future, due to the strong climatic changes evidences in the planet. The aim of this work is to estimate the water availability variation trends in the Paracatu river basin, from the beginning until the end of this century, considering two contrasting climate change scenarios, the first one to take account of high CO2 emissions (A2) and the other one for low emissions (B2). To achieve this objective, the monthly precipitation downscaling was accomplished, using data from 2001 to 2099 simulated by the Hadley Centre´s global circulation model (HadCM3). The precipitations were used as data input in a precipitation-flow model, which made possible the estimate of the minimum discharges in 21 gauged stations distributed in the basin. For the A2 scenario, an increase trend was verified in the water availability in all of the stations from 2001 to 2099, varying from 31 to 131%. For the B2 scenario no significant trend was verified.

Programa computacional para geração de séries sintéticas de precipitação

A computational model was developed to generate synthetic series of rainfall using the method developed by OLIVEIRA (2003). The software was developed in Borland Delphi 6.0 environment. The input data come from the daily precipitation data in the standardized format of the National Water Agency (ANA). The software is capable to generate synthetic series of daily rainfall containing the amount and the duration of the rainfall, and the standardized event time of the maximum instantaneous intensity. The generated synthetic series are stored in text-formatted files that may be accessed by others softwares and/or electronic datasheets. There were also presented graphs and tables format, to easily evaluate the performance of the method developed.

Assessing rainfall erosivity indices through synthetic precipitation series and artificial neural networks

The rainfall parameter that expresses the capacity to promote soil erosion is called rainfall erosivity (R), and is commonly represented by the indexes EI30 and KE>25. The calculations of these indexes requires pluviographical records, that are difficult to obtain in Brazil. This paper describes the use of synthetic rainfall series to compute EI30 and KE>25 in Espirito Santo State (Brazil). Artificial neural networks (ANNs) were also developed to spatially interpolate R values in Espirito Santo. EI30 and KE>25 indexes values were close to those calculated on a homogeneous area according to the similarity of rainfall distribution; indicating the applicability of the use of synthetic rainfall series to estimate the R factor. ANNs had a better performance than Inverse Distance Weighted and Kriging to spatially interpolate rainfall erosivity values in the State of Espirito Santo.

Modelo para a determinação do espaçamento entre desaguadouros em estradas não pavimentadas

As estradas nao pavimentadas sao de fundamental importância para o desenvolvimento social e economico do Brasil, sendo a erosao provocada pela agua no leito e nas margens destas estradas um dos principais fatores para sua degradacao. Neste artigo, apresenta-se um novo modelo para a determinacao do espacamento entre desaguadouros em estradas nao pavimentadas e, consequentemente, para a reducao dos problemas associados a erosao hidrica. Utilizando o modelo de ondas cinematicas, determina-se o hidrograma de escoamento superficial no canal de drenagem da estrada e, a partir deste, e calculada a tensao provocada pelo escoamento. Sempre que a tensao cisalhante causada pelo escoamento supera a tensao critica para cisalhamento do solo ocorre o seu desprendimento. A diferenca entre essas tensoes cisalhantes e multiplicada pela erodibilidade do solo e pela area em que ocorre a aplicacao da tensao cisalhante para estimar a perda de solo provocada pelo escoamento. O espacamento maximo entre desaguadouros e obtido, comparando-se a perda de solo provocada pelo escoamento com a perda de solo toleravel. O comprimento maximo do canal e aquele para o qual a perda toleravel e atingida. O modelo permite determinar o espacamento entre desaguadouros considerando as caracteristicas das areas que contribuem para o escoamento e a resistencia do solo. As simulacoes realizadas mostraram que o modelo e sensivel as alteracoes na erodibilidade e na tensao critica de cisalhamento do solo, bem como a declividade do canal, permitindo ainda que, por meio da alteracao no aprofundamento toleravel para o canal, os espacamentos possam ser ampliados ou reduzidos.