Nori Paulo Griebeler

Uso de vinhaça e impactos nas propriedades do solo e lençol freático

Usually stillage presents high concentrations of nitrate, potassium and organic matter. Its utilization may change a soils characteristics and modify its chemical properties, increasing the availability of some elements for plants. On the other hand, stillage may also promote change in physical properties of soil in two different ways: these changes can improve soil aggregation, increasing soil water infiltration capacity and, consequently, increasing leaching of ions, in such a way to contaminate the groundwater when in high concentrations, as well as to promote dispersion of soil particles, contributing for a decrease in its infiltration rate and elevation of runoff, with possible contamination of surface water. Due to the fact that there are different types of soil and stillage composition, the research results found are very variable, however, agreement exists that its application must be made according to cation exchange capacity of soil.

Modelo para o dimensionamento e a locação de sistemas de terraceamento em nível

Water erosion is one of the main problems of agricultural lands degradation, causing largess damages to the society. Because of these damages, it becomes necessary the development of techniques that allow the increase of the efficiency of soil conservation practices. With this objective, a model was developed for design and location of level terracing systems using digital models of elevation of the land generated in geographic information systems (GIS). In order to facilitate the application of the developed model, it was elaborated a software. The results show that the model offers as the principal advantage the design of each terrace considering the existent conditions in the specific area that will contribute with the runoff to itself. The other advantage of the developed model is the possibility of simulations accomplishment, allowing the observation and the accompaniment of the changes caused in the terracing system in function of the changes in the soil use and handling.

Erodibility and critical shear stress on unpaved road soils

The absence of an adequate drainage system in unpaved roads is one of the main factors for their degradation. For adequate planning knowledge of the resistance parameters of soil is necessary. This study had as its objective the determinatiom of the erodibility and critical shear stress of unpaved road soils. For this work, a runoff simulator was directly installed on road channels, under natural conditions. Different flow depths were applied and the soil loss was measured for each depth. The erodibility and the critical shear stress were determined through adjusted curves relating soil disaggregation and flow shear stress. The results showed variations in erodibility and in critical shear stress values of the roads. The erodibility values obtained, when compared with values observed in the literature, evidenced high susceptibility to the erosion for road conditions. These values were higher on silt loam and sandy soils. The critical shear stress values were similar to those observed in other publications.

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.

Equipamento para determinação da erodibilidade e tensão crítica de cisalhamento do solo em canais de estradas

Water erosion on unpaved roads is directly related with poor drainage. The knowledge of the soil erodibility and critical shear stress is essential for correct design of drainage systems. In this paper equipment was developed which allows to simulate the surface runoff in the road channels and to determine, consequently, the soil erodibility and the critical shear stress for the soil. The equipment consists of a water reservoir, a box to control water level, a channel where the surface runoff simulation is made and a system to store the water and the sediments which are detached by surface runoff. The equipment had a good performance to determine the soil erodibility and the critical shear stress for the soil; however it has inconvenience with respect to labor and the amount of water necessary.

Software para o planejamento e a racionalização do uso de sistemas de terraceamento em nível

The development of techniques that allow the increase of the efficiency of practices of soil conservation is necessary front to the great damages caused by the erosion. In this sense, software was elaborated based on Geographical Information System that allows the planning of level terracing systems in a more rational way, considering the existent space variations in the land. As entrance data to the software, it should be supplied with elevation and slope images characteristics and type, the use and the handling of the soil, the methodology for the calculation of the spacing among terraces and, the recommendation of the type of advised terrace. As results the software supplies a map with the terracing system and a report with information for the implementation of the system.

Variabilidade espacial e temporal da precipitação pluvial na bacia hidrográfica do Ribeirão João Leite-GO

The pluvial precipitation is the main hydrology variable input in the hydrological cycle and the knowledge of their spatial and temporal behavior is basic material for hydrological studies, watershed and water resource management, among others. The surface water produced in this basin is essential to the development of the Axis Anapolis-Goiânia-Brasilia and recently, with the increasing of water demand, it has been reported conflicts by the water use. Thus, it appears that the development of hydrological studies aimed for better understanding and utilization of water resources are strategic for the development of the region. In this way, this work purpose to map the average monthly and annual precipitation in the Joao Leite watershed, using geostatistical techniques. It was evaluated the spherical, exponential and gaussian semivariogram models, adjusted by the weighted least squares method, being the model used for mapping by kriging the one that produced the lowest average error indicated by cross validation. It was found a good performance of geostatistical techniques in mapping the average monthly and annual precipitation, indicated by small errors, which can be highlighted the exponential model, with the best results in the most of the studied events.

Sequências de dias chuvosos: fator de risco à colheita em Goiás

O objetivo deste trabalho foi estabelecer sequencias de dias chuvosos como fator de risco a colheita no Estado de Goias. Para isso, foram utilizadas series historicas pluviometricas, com periodo de base de, no minimo, 17 anos referentes a 36 estacoes pluviometricas localizadas neste Estado. As sequencias de dias chuvosos foram separadas por uma rotina computacional para os meses de dezembro, janeiro, fevereiro e marco. Para o estudo de probabilidade destas sequencias, utilizou-se a Distribuicao Binominal Negativa Truncada (DBNT). A aderencia da distribuicao as sequencias de dias chuvosos foi verificada, utilizando-se do teste de Qui-quadrado (χ2). Os resultados foram espacializados, de modo a facilitar a visualizacao da distribuicao espacial das sequencias de dias chuvosos para os meses estudados. Verificou-se que o risco de chuva na colheita varia localmente. As maiores probabilidades de ocorrencia de sequencias com dois dias chuvosos ocorreram nas regioes centro, sudoeste e sul, e tres dias na regiao central e entorno. Ocorrencia de sequencias com quatro dias chuvosos ou mais apresentou baixa probabilidade.

Rotina computacional para a determinação da velocidade de sedimentação das partículas do solo em suspensão no escoamento superficial

O presente trabalho teve como objetivo desenvolver uma rotina computacional para a determinacao da velocidade de deposicao de particulas em suspensao no escoamento superficial, verificar sua aplicacao por intermedio de modelo de transporte de sedimentos e comparar os resultados obtidos com dados experimentais. Empregou-se na rotina o processo iterativo de Newton-Rapshon para a solucao das equacoes empregadas na determinacao da velocidade de deposicao de particulas em suspensao no escoamento superficial, e na solucao da equacao do transporte de sedimentos empregou-se a tecnica das diferencas finitas. Essas rotinas foram empregadas na implementacao do modelo MTSES (Modelo para Transporte de Solutos no Solo e no Escoamento Superficial). As velocidades de queda das particulas obtidas pela rotina desenvolvida, em media, foram superestimadas, com erro relativo medio de 0,63%, o que possibilitou a utilizacao da rotina desenvolvida no MTSES. O modelo MTSES superestimou o total de sedimentos transportados pelo escoamento superficial para todas as intensidades de precipitacao empregadas neste estudo, com variacoes porcentuais de 15,6 a 58,3%.

DETERMINAÇÃO DE INCREMENTO DE ALTURA DE CAMALHÃO NA INTEGRAÇÃO TERRAÇO-ESTRADA

Hydric erosion is one of the major causes of agricul-tural land degradation, resulting in economic, social, and environmental losses. Conservation practices are important tools to reduce erosion risks and their correct design is fundamental to success. Models for designing both rural roads and terraces systems are currently used, however, their integration is not available. The integration of terracing systems and runoff coming from roads, although recommended and utilized, can increase erosion risk and terraces disruption, without a proper dimensioning practice. So, this study aimed to develop a terrace-road integration model and a calculation routine that allows this integration. The routine was used for sizing an integrated conservation system. The results show that although in some terraces the increase in height is small, dimensioning is necessary, because it allows to identify the critical points of integration, and, without it, the terrace would go through storage problems. It was concluded that the methodology presented made possible to calculate the increase in the recommended height for terraces, as a viable alternative, with a small increase in the terrace height. The calculation routine application was simple, but the development of computational tools would facilitate its use and reduce miscalculation risks.