Modelagem do transporte de sedimentos na alta Bacia do Córrego Cachoeirinha (Rio Claro, SP) através do software Soil and Water Assessment Tool (SWAT)

This study aimed to simulate and evaluate the sediment transport in Upper Basin Stream Cachoeirinha in Rio Claro, SP, and compare the results with previous studies performed in the same basin. The modeling software used in this study was Soil and Water Assessment Tool (SWAT), which is a very comprehensive tool that discusses many physical processes. In this work, the hydrosedimentological processes were treated, aiming to understand the sediment production and transport. The Basin Stream Cachoeirinha has an area with predominantly agricultural use, especially sugar cane. The database for inclusion in software was constructed from the following elements: climatic, topographical, soil type and use and land cover of the area, also including the parameters of Modified Universal Soil Loss Equation (MUSLE). The analysis was conducted for a period of 16 years (1994-2010), which is the range of data available from CEAPLA. The results were analyzed in terms of annual runoff and sediment yield. The average sediment delivery in the simulation was 0.94 t/ha/year, while the maximum annual contribution was 7.28 t/ha/year

Estimativa da erosão na microbacia do Córrego do Gambá no município de Monte Alto, SP

Pós-graduação em Agronomia (Ciência do Solo) - FCAV

Erosão em taludes de corte: métodos de proteção e estabilização

This work addresses the erosion caused by rain, describing their steps and factors that most influence the intensity and volume of transported material. The work presents the Universal Soil Loss Equation that quantifies the erosion, with the influence of different factors that affect it. The following notes the occurrence of this process in cutting slopes. They suffer with removal of the vegetation and surface soil layer, making them even more susceptible to this process. In this way it's necessary a protection model for the slopes. Some protection methods are presents with their main features, advantages and disadvantages, implementation process, especially to survey the approximate cost of each method and their application restrictions

Avaliação dos modelos de predição da erosão hídrica MEUPS e WEPP: contribuição em bacias hidrográficas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Geographic information system-based decision support for soil conservation planning in Tajikistan

Soil erosion on sloping agricultural land poses a serious problem for the environment, as well as for production. In areas with highly erodible soils, such as those in loess zones, application of soil and water conservation measures is crucial to sustain agricultural yields and to prevent or reduce land degradation. The present study, carried out in Faizabad, Tajikistan, was designed to evaluate the potential of local conservation measures on cropland using a spatial modelling approach to provide decision-making support for the planning of spatially explicit sustainable land use. A sampling design to support comparative analysis between well-conserved units and other field units was established in order to estimate factors that determine water erosion, according to the Revised Universal Soil Loss Equation (RUSLE). Such factor-based approaches allow ready application using a geographic information system (GIS) and facilitate straightforward scenario modelling in areas with limited data resources. The study showed first that assessment of erosion and conservation in an area with inhomogeneous vegetation cover requires the integration of plot-based cover. Plot-based vegetation cover can be effectively derived from high-resolution satellite imagery, providing a useful basis for plot-wise conservation planning. Furthermore, thorough field assessments showed that 25.7% of current total cropland is covered by conservation measures (terracing, agroforestry and perennial herbaceous fodder). Assessment of the effectiveness of these local measures, combined with the RUSLE calculations, revealed that current average soil loss could be reduced through low-cost measures such as contouring (by 11%), fodder plants (by 16%), and drainage ditches (by 53%). More expensive measures such as terracing and agroforestry can reduce erosion by as much as 63% (for agroforestry) and 93% (for agroforestry combined with terracing). Indeed, scenario runs for different levels of tolerable erosion rates showed that more cost-intensive and technologically advanced measures would lead to greater reduction of soil loss. However, given economic conditions in Tajikistan, it seems advisable to support the spread of low-cost and labourextensive measures.

Bodenerosions-Gefährdungskarte der Schweiz

Die Bodenerosions-Gefährdungskarte gibt einen nationalen Überblick über das Abtragsrisiko der Schweizer Böden und vor allem für die Ackerböden. Mit Hilfe einer angepassten Version des empirischen Erosionsmodells «Universal Soil Loss Equation» (USLE) wurde die langfristige Bodenerosionsgefährdung flächendeckend im Hektarraster berechnet. Die Bodenerosions-Gefährdungskarte soll den Kantonen als Grundlage dienen, detaillierte Karten zu erstellen oder besonders gefährdete Gebiete vertieft zu untersuchen. Unter der Annahme, dass alle Ackerflächen mit dem Pflug bearbeitet und keine Zwischenfrüchte angebaut werden, weisen bei heutiger Fruchtfolgegestaltung 61 % aller Ackerflächen einen langjährigen mittleren Bodenabtrag von unter zwei Tonnen pro Hektare und Jahr auf und sind damit als wenig erosionsgefährdet einzustufen. 22 % liegen im kritischen Bereich zwischen zwei und vier Tonnen pro Hektare und Jahr, 17 % sind mit mehr als vier Tonnen pro Hektare und Jahr als stark erosionsgefährdet zu bezeichnen. Die räumliche Verteilung der Abtragswerte zeigt ein sehr heterogenes Muster innerhalb der Hauptackerbau-Regionen ohne räumlich konzentrierte Schwerpunktregionen. In einer Szenario-Berechnung, bei der die Bodenbearbeitung mit dem Pflug durch Direktsaat sowie Winterbrache durch Zwischenkulturanbau flächendeckend ersetzt werden, reduziert sich das Bodenerosionsrisiko im Durchschnitt um rund zwei Drittel.

Current and potential water erosion estimation with RUSLE3D in Castellon province (Spain)

The purpose of this study was the estimation of current and potential water erosion rates in Castellon Province (Spain) using RUSLE3D (Revised Universal Soil Loss Equation-3D) model with Geographical Information System (GIS) support. RUSLE3D uses a new methodology for topographic factor estimation (LS factor) based on the impact of flow convergence allowing better assessment of sediment distribution detached by water erosion. In RUSLE3D equation, the effect that vegetation cover has on soil erosion rate is reflected by the C factor. Potential erosion indicates soil erosion rate without considering C factor in RUSLE3D equation. The results showed that 57% of estimated current erosion does not exceed 10 t/ha.year (low erosion). In the case of potential erosion rates, 5% of the area of Castellon Province does not exceed 10 t/ha.year but 55% exceed 200 t/ha.year. Based on these results, the current vegetation cover of Castellon Province is adequate but needs to be conserved to avoid an increase in the current soil erosion rates as shown by potential erosion rates.

Modelización de la pérdida de suelo en sierras del Sudoeste de la Provincia de Buenos Aires

El modelo U.S.L.E. (Universal Soil Loss Equation), desarrollado por Wischmeier y Smith en 1978, es un modelo paramétrico creado para estimar la pérdida anual de suelo. Engloba, dentro de los cinco factores intervinientes, todas las características de la cuenca, incluyendo tanto aspectos físicos como características edáficas, geológicas y geomorfológicas, sin olvidar las relacionadas con el clima, y el tipo de manejo y uso del suelo. El objetivo del trabajo fue estimar la pérdida de suelo a nivel de la cuenca hidrográfica del Arroyo Belisario, ubicada en el Partido de Tornquist, en el Sudoeste de la Provincia de Buenos Aires. Más de 1.200 ha (aproximadamente 50% de la cuenca), presentaron pérdidas de suelo mayores a las 50 tn.ha-1.año-1. Se observó que los factores K y LS son determinantes de los elevados valores presentes en la cabecera de la cuenca. La elaboración de la cartografía correspondiente a cada factor de la U.S.L.E se realizó con el Sistema de Información Geográfica Idrisi Andes. Se concluye que el modelo fue aplicado de manera correcta en la cuenca del Arroyo Belisario, brindando resultados que facilitarán la toma de decisiones para un futuro ordenamiento territorial.

Ordenación agrohidrológica de la cuenca del Etang Pouillet Departamento del Sudeste Haití.

La cuenca del “Etang Pouillet” (Departamento del Sudeste, Haití), presenta unas tasas de erosión muy elevadas debido a la deforestación y a la práctica de la agricultura sin técnicas de conservación de suelos, lo que constituye un grave problema desde el punto de vista medioambiental y social, ya que la pérdida de productividad del suelo pone en peligro la seguridad alimentaria de los habitantes de la cuenca, mayoritariamente agricultores. Para la evaluación de las tasas de pérdidas de suelo se ha utilizado la metodología propuesta por la Ecuación Universal de Pérdidas de Suelo, U.S.L.E. (Universal Soil Loss Equation). Dicha evaluación estima pérdidas de suelo calificadas de altas (50 – 200 t ha/año) o muy altas (> 200 t ha/año) en casi el 90% de la superficie de la cuenca. Debido a las altas tasas de pérdidas de suelo, se propone una intervención integral de la cuenca. En dicha intervención se combinarán actuaciones técnicas de conservación de suelos para frenar la degradación del mismo y se incidirá en el trabajo con las comunidades para mitigar el impacto que realizan sobre el medio y asegurar una mayor durabilidad de las actuaciones correctoras.

Prototype emitter for use in subsurface drip irrigation: Manufacturing, hydraulic evaluation and experimental analyses

The current research aims to analyse theoretically and evaluate a self-manufactured simple design for subsurface drip irrigation (SDI) emitter to avoid root and soil intrusion. It was composed of three concentric cylindrical elements: an elastic silicone membrane; a polyethylene tube with two holes drilled on its wall for water discharge; and a vinyl polychloride protector system to wrap the other elements. The discharge of the emitter depends on the change in the membrane diameter when it is deformed by the water pressure. The study of the operation of this emitter is a new approach that considers mechanical and hydraulic principles. Thus, the estimation on the membrane deformation was based on classical mechanical stress theories in composite cylinders. The hydraulic principles considered the solid deformation due to force based on water pressure and the general Darcy–Weisbach head-loss equation. Twenty emitter units, with the selected design, were handcrafted in a lathe and were used in this study. The measured pressure/discharge relationship for the emitters showed good agreement with that calculated by the theoretical approach. The variation coefficient of the handcrafted emitters was high compared to commercial emitters. Results from field evaluations showed variable values for the relative flow variation, water emission uniformity and relative flow rate coefficients, but no emitter was obstructed. Therefore, the current emitter design could be suitable for SDI following further studies to develop a final prototype.

Efeitos da mecanização agrícola da cultura da cana-de-açúcar nos processos erosivos: dimensionamento de terraços com base na Equação Universal de Perdas de Solo (EUPS)

A cultura da cana-de-açúcar é a segunda maior movimentação econômica na cadeia do agronegócio no Brasil. Gera riquezas através da fabricação de açúcar, etanol e cogeração de energia elétrica, além de outros subprodutos. Considerada fonte de energia renovável, a cana-de- açúcar a princípio tinha sua imagem associada a impactos negativos principalmente devido as queimadas realizadas nas lavouras para colheita manual. Nos últimos anos, baseado em decretos e no Protocolo Agro-ambiental, essa prática vem sendo abolida. Para se manter e até mesmo aumentar o rendimento das colhedoras nos canaviais, os gestores têm adotado práticas para reduzir os terraços agrícolas, com impacto nos sistemas de conservação de solos. Assim, este trabalho teve como objetivo identificar os impactos ambientais provocados pela mecanização agrícola decorrente do mau manejo e dimensionamento dos mecanismos de conservação do solo. Neste estudo também se realizou uma análise à Equação Universal de Perdas de Solo (EUPS), como ferramenta para o dimensionamento de terraços agrícolas. O estudo foi realizado em uma microbacia hidrográfica, denominada Ribeirão da Bocaina, localizada na UGRHI-13 (Tietê - Jacaré). Foi possível identificar a variabilidade amostral do solo para o dimensionamento conservacionista, gerando curvas de nível com Desníveis Verticais (D.V) desuniformes, contrariando a sistemática atual de terraços que respeita cotas múltiplas ou mesmo dimensionamentos empiristas, segundo o conhecimento local e o histórico recente da área. Algumas sugestões também foram feitas afim de torná-la uma ferramenta ainda mais eficiente, considerando condições particulares à cultura da cana-de-açúcar, tais como a influência da palhada, sulcos de plantio e diversos tipos de terraços como meios de controle à erosão. A metodologia foi satisfatória, no que tange a compreensão pelos meios de correlação entre as práticas conservacionistas e modelos de predição de perda de solo, trazendo luz à ciência na interpretação das ferramentas existentes e as lacunas a serem preenchidas.

USLE and WEPP Soil Erosion Models: Their Applicability and Use in Generating Cover Values to Stabilize Soil in the Los Alamos, New Mexico Area

Soil erosion is a naturally occurring process that involves the detachment, transport, and deposition of soil particles. Disturbances such as thinning and wildfire can reduce cover greatly and increase erosion rates. Forest managers may use erosion prediction tools, such as the Universal Soil Loss Equation (USLE) and Water Erosion Prediction Project (WEPP) to estimate erosion rates and develop techniques to manage erosion. However, it is important to understand the differences and the applications of each model. Erosion rates were generated by each model and the model most applicable to the study site, Los Alamos, New Mexico was determined. It was also used to find the amount of cover needed to stabilize soil. The USLE is a simpler model and less complicated than a computer model like WEPP, and thus easier to manipulate to estimate cover values. Predicted cover values were compared to field cover values. Cover is necessary to establish effective erosion control guidelines.

A daily rainfall erosivity model for Western Amazonia

Rainfall erosivities as defined by the R factor from the universal soil loss equation were determined for all events during a two-year period at the station La Cuenca in western Amazonia. Three methods based on a power relationship between rainfall amount and erosivity were then applied to estimate event and daily rainfall erosivities from the respective rainfall amounts. A test of the resulting regression equations against an independent data set proved all three methods equally adequate in predicting rainfall erosivity from daily rainfall amount. We recommend the Richardson model for testing in the Amazon Basin, and its use with the coefficient from La Cuenca in western Amazonia.

Improved slope adjustment functions for soil erosion prediction

Numerous studies in the last 60 years have investigated the relationship between land slope and soil erosion rates. However, relatively few of these have investigated slope gradient responses: ( a) for steep slopes, (b) for specific erosion processes, and ( c) as a function of soil properties. Simulated rainfall was applied in the laboratory on 16 soils and 16 overburdens at 100 mm/h to 3 replicates of unconsolidated flume plots 3 m long by 0.8 m wide and 0.15 m deep at slopes of 20, 5, 10, 15, and 30% slope in that order. Sediment delivery at each slope was measured to determine the relationship between slope steepness and erosion rate. Data from this study were evaluated alongside data and existing slope adjustment functions from more than 55 other studies from the literature. Data and the literature strongly support a logistic slope adjustment function of the form S = A + B/[1 + exp (C - D sin theta)] where S is the slope adjustment factor and A, B, C, and D are coefficients that depend on the dominant detachment and transport processes. Average coefficient values when interill-only processes are active are A - 1.50, B 6.51, C 0.94, and D 5.30 (r(2) = 0.99). When rill erosion is also potentially active, the average slope response is greater and coefficient values are A - 1.12, B 16.05, C 2.61, and D 8.32 (r(2) = 0.93). The interill-only function predicts increases in sediment delivery rates from 5 to 30% slope that are approximately double the predictions based on existing published interill functions. The rill + interill function is similar to a previously reported value. The above relationships represent a mean slope response for all soils, yet the response of individual soils varied substantially from a 2.5-fold to a 50-fold increase over the range of slopes studied. The magnitude of the slope response was found to be inversely related ( log - log linear) to the dispersed silt and clay content of the soil, and 3 slope adjustment equations are proposed that provide a better estimate of slope response when this soil property is known. Evaluation of the slope adjustment equations proposed in this paper using independent datasets showed that the new equations can improve soil erosion predictions.

Development of a sediment yield model for South East Ghana in the regions around Lake Volta

Soil erosion is one of the most pressing issues facing developing countries. The need for soil erosion assessment is paramount as a successful and productive agricultural base is necessary for economic growth and stability. In Ghana, a country with an expanding population and high potential for economic growth, agriculture is an important resource; however, most of the crop production is restricted to low technology shifting cultivation agriculture. The high intensity seasonal rainfall coincides with the early growing period of many of the crops meaning that plots are very susceptible to erosion, especially on steep sided valleys in the region south of Lake Volta. This research investigated the processes of soil erosion by rainfall with the aim of producing a sediment yield model for a small semi-agricultural catchment in rural Ghana. Various types of modelling techniques were considered to discover those most applicable to the sub-tropical environment of Southern Ghana. Once an appropriate model had been developed and calibrated, the aim was to look at how to enable the scaling up of the model using sub-catchments to calculate sedimentation rates of Lake Volta. An experimental catchment was located in Ghana, south west of Lake Volta, where data on rainstorms and the associated streamflow, sediment loads and soil data (moisture content, classification and particle size distribution) was collected to calibrate the model. Additional data was obtained from the Soil Research Institute in Ghana to explore calibration of the Universal Soil Loss Equation (USLE, Wischmeier and Smith, 1978) for Ghanaian soils and environment. It was shown that the USLE could be successfully converted to provide meaningful soil loss estimates in the Ghanaian environment. However, due to experimental difficulties, the proposed theory and methodology of the sediment yield model could only be tested in principle. Future work may include validation of the model and subsequent scaling up to estimate sedimentation rates in Lake Volta.