The main objective of this study was to test the sediment prediction capability of the Water Erosion Prediction Project (WEPP) model on tropical watersheds and also identify erosion hotspot areas. The maximum total discharge at the watershed outlet was 3,462m3/s. Runoff also varied with soil type in all four watersheds. The highest average annual runoff depths occurred on areas with high percentage of ferralic cambisols and humic acrisols soils. The lowest runoff depth was in areas with high percentage of rhodic ferralsols and eutric leptosols soils in Kibungo chini. The soil loss and sediment yield had the same relationship as the runoff changes. The highest and lowest total average annual soil loss rate was estimated in Mfizigo juu and Kibungo chini respectively. The cultivated land contributed to over 81% of soil loss and 86% of sediment yield in all four scenarios. The overall spatial results maps indicated WEPP model can help managers to implement necessary precaution measures to prevent sediment yield and soil erosion.

Submitted by VERA LÚCIA DA SILVA FARIAS null (verlucbio@yahoo.com.br) on 2017-01-12T20:11:31Z No. of bitstreams: 1 Tese_Vera_Lucia_da_Silva_Farias.pdf: 2109156 bytes, checksum: a352f68e4cb2df0cff49ade4c7573779 (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-01-16T17:36:32Z (GMT) No. of bitstreams: 1 farias_vls_dr_jabo.pdf: 2109156 bytes, checksum: a352f68e4cb2df0cff49ade4c7573779 (MD5) / Made available in DSpace on 2017-01-16T17:36:32Z (GMT). No. of bitstreams: 1 farias_vls_dr_jabo.pdf: 2109156 bytes, checksum: a352f68e4cb2df0cff49ade4c7573779 (MD5) Previous issue date: 2016-12-16 / Com a crescente preocupação com as perdas de fósforo na água de enxurrada e sedimentos erodidos enriquecidos com P, que podem aumentar o risco de eutrofização dos corpos d´água superficiais, o interesse no uso de modelos que avaliam os impactos do uso do solo, tornou-se importante. O modelo WEPP, tem uma ampla gama de aplicabilidade, uma vez que pode ser usado para simular processos de erosão, escoamento e transporte de elementos orgânicos e químicos. Entretanto, no Brasil, não há casos em que um algoritmo tenha sido associado ao WEPP para modelar o transporte de P. Assim, o objetivo deste trabalho foi avaliar o desempenho de modelos para estimar as perdas de fósforo disponível, no sedimento erodido predito pelo WEPP, em uma pequena bacia hidrográfica. O presente trabalho foi realizado em área localizada no município de Tabapuã, noroeste do Estado de São Paulo. Os dados para alimentar o banco de dados do WEPP basearam-se nos componentes: climático, hidrológico e desenvolvimento vegetal. Os sedimentos erodidos foram classificados em: frações primárias, areia, silte, agregados pequenos e grandes. Com tais frações foi calculada a taxa de enriquecimento por fósforo com o WEPP (WER). Outros dois algoritmos foram utilizados para estimar o fósforo transportado com o sedimento erodido: ln(ER) = 2,682 – 0,278 ln(Sed) e) ln(ER) = 2 - 0,2 ln(Sed). Para a validação das estimativas de P nos sedimentos, utilizaram-se os critérios: o coeficiente de Nash-Sutcliffe (NS), o erro quadrático médio (RMSE), o coeficiente de massa residual (CRM) e o índice de concordância (d). Os modelos testados para estimar as taxas de enriquecimento do sedimento erodido e enxurrada por P são eficientes, quando em uso com as predições do Water Erosion Prediction Project (WEPP). As taxas de enriquecimento obtidas com o WEPP (WER), equação ln(ER) = 2,682 – 0,278 ln(Sed) e ln(ER) = 2 - 0,2 ln(Sed), respectivamente, apresentaram coeficiente de Nash-Sutcliffe (NS) próximo de 1. As perdas de P com o sedimento e enxurrada apresentaram moderado grau de dependência especial (GDE), enquanto que a erosão estimada pelo WEPP apresentou alto GDE. Perdas de fósforo solúvel com a enxurrada acima de 0,02 mg L-1, valor crítico para eutrofização, podem ser obtidas em 81% da área da bacia com uma probabilidade superior a 75%. / With the growing concern over phosphorus losses with the runoff water and eroded sediment enriched with P that can increase the risk of eutrophication of surface water bodies, interest in the use of models that assess the impacts of land use, has if important. The WEPP model has a wide range of applicability, since it can be used to simulate erosion, drainage and transport and organic chemicals. However, in Brazil, there aren’t cases in which an algorithm has been associated with the WEPP to model the transport P. Thus, the objective with this study was to evaluate the performance of mode loss of phosphorus with eroded sediment in agricultural environment to estimate phosphorus losses available in the sediment eroded predicted the WEPP in a small catchment. This work was carried out in an area located in the municipality of Tabapuã, northwest of São Paulo. The sediment losses were estimated with the WEPP model. Two approaches (P-empirical) estimated ER according to an empirical relationship, and the other approach used WER calculated by WEPP (P-WEPP). Models to estimate enrichment rates of the sediment (Sed) and runoff with the Water Erosion Prediction Project (WEPP), WER - WEPP, an equation ln(ER) = 2.682 - 0.278 ln(Sed) and ln(ER) = 2 - 0.2 ln (Sed) present coefficient of Nash-Sutcliffe (NS) next 1.

Submitted by Mario BC (mario@bc.ufrpe.br) on 2016-08-15T15:18:46Z No. of bitstreams: 1 Waldemir Pereira de Souza.pdf: 2049790 bytes, checksum: cfb86b171794e47f98d211aa32854b10 (MD5) / Made available in DSpace on 2016-08-15T15:18:46Z (GMT). No. of bitstreams: 1 Waldemir Pereira de Souza.pdf: 2049790 bytes, checksum: cfb86b171794e47f98d211aa32854b10 (MD5) Previous issue date: 2015-09-18 / Soil erosion is an irreversible phenomenon that causes soil degradation and deterioration of water quality, therefore, models such as water erosion prediction project (WEPP) physical base can be increasingly used to assess erosion rill in semiarid environment. The objective was to quantify the rill erosion with relationships the WEPP and evaluate the hydraulic conditions of runoff under conditions of rill preformed. The experiment was conducted in the exu watershed in Serra Talhada, semiarid region of Pernambuco where was prepared 16 rill preformed who underwent different flow levels: 5.87 L min-1, 12.10 L min-1, 20.33 L min-1 and 27.57 L min-1 in Entisol fluvent. With the performance of the concentration of runoff in rill experimental produced flow regimes slow turbulent in the largest flows applied characterizing the characterizing the occurrence of erosion in rill. The erodibility values in rill (Kr)was 0.0011 kgN-1s-1 and critical shear corresponds to 1.91 Pa. The values of soil losses to erosion rill were considered high for Entisol fluvent behaving smaller particle size composition with a higher percentage of sand. / A erosão do solo é um fenômeno irreversível que causa a degradação do solo e a deterioração da qualidade da água, dessa forma, modelos como o Projeto de Predição de Erosão Hídrica (WEPP) de base física podem ser cada vez mais utilizados na avaliação da erosão do solo em sulcos em ambiente semiárido. Objetivou-se quantificar a erosão em sulcos com as relações de erosão do WEPP e avaliar as condições hidráulicas do escoamento superficial sob condições de sulcos pré-formados. O experimento foi realizado na Bacia do Riacho Exu, no município de Serra Talhada, região semiárida de Pernambuco onde foram preparadas parcelas experimentais que consistiram em 16 sulcos pré-formados que foram submetidos a aplicação de diferentes níveis de vazão: 5,87 Lmin-1, 12,10 Lmin-1, 20,33 Lmin-1 e 27,57 Lmin-1 em Neossolo Flúvico. Com a atuação da concentração do escoamento superficial nos sulcos experimentais produziram regimes de escoamento na faixa de turbulento lento nos maiores fluxos aplicados caracterizando a ocorrência da erosão em sulcos. Os valores de erodibilidade em sulcos (Kr) foi de 0,0011 KgN-1s-1 e a tensão crítica de cisalhamento corresponde a 1,91 Pa. Os valores das perdas de solo para a erosão em sulcos foram consideradas altas para um Neossolo Flúvico comportando menor composição granulométrica com maior percentagem de areia.

<p>Hydrological modeling has been a valuable tool to understand the processes governing water distribution, quantity, and quality of the planet Earth. Through models, one has been able to grasp processes such as runoff, soil moisture, soil erosion, subsurface drainage, plant growth, evapotranspiration, and effects of land use changes on hydrology at field and watershed scales. The number and diversity of water-related challenges are vast and expected to increase. As a result, current models need to be under continuous modifications to extend their application to more complex processes. Several models have been extensively developed in recent years. These models include the Soil and Water Assessment Tool (SWAT), Variable Infiltration Capacity (VIC) model, MIKE-SHE, and the Water Erosion Prediction Project (WEPP) model. The latter, although it is a well-validated model at field scales, the WEPP watershed model has been limited to small catchments, and almost no research has been introduced regarding water quality issues (only one study).</p><p>In this research, three objectives were proposed to improve the WEPP model in three areas where either the model has not been applied, or modifications can be performed to improve algorithms of the processes within the model (e.g. erosion, runoff, drainage). The enhancements impact the WEPP model by improving the current stochastic weather generation, extending its applicability to subsurface drainage estimation, and formulating a new routing model that allows future incorporation of transport of reactive solutes.</p><p>The first contribution was development of a stochastic storm generator based on 5-min time resolution and correlated non-normal Monte Carlo-based numerical simulation. The model considered the correlated and non-normal rainstorm characteristics such as time between storms, duration, and amount of precipitation, as well as the storm intensity structure. The model was tested using precipitation data from a randomly selected 5-min weather station in North Carolina. Results showed that the proposed storm generator captured the essential statistical features of rainstorms and their intensity patterns, preserving the first four moments of monthly storm events, good annual extreme event correspondence, and the correlation structure within each storm. Since the proposed model depends on statistical properties at a site, this may allow the use of synthetic storms in ungauged locations provided relevant information from a regional analysis is available.</p><p>A second development included the testing, improvement, and validation of the WEPP model to simulate subsurface flow discharges. The proposed model included the modification of the current subsurface drainage algorithm (Hooghoudt-based expression) and the WEPP model percolation routine. The modified WEPP model was tested and validated on an extensive dataset collected at four experimental sites managed by USDA-ARS within the Lake Erie Watershed. Predicted subsurface discharges show Nash-Sutcliffe Efficiency (NSE) values ranging from 0.50 to 0.70, and percent bias ranging from -30% to +15% at daily and monthly resolutions. Evidence suggests the WEPP model can be used to produce reliable estimates of subsurface flow with minimum calibration.</p><p>The last objective presented the theoretical framework for a new hillslope and channel-routing model for the Water Erosion Prediction Project (WEPP) model. The routing model (WEPP-CMT) is based on catchment geomorphology and mass transport theory for flow and transport of reactive solutes. The WEPP-CMT uses the unique functionality of WEPP to simulate hillslope responses under diverse land use and management conditions and a Lagrangian description of the carrier hydrologic runoff at hillslope and channel domains. An example of the model functionality was tested in a sub-catchment of the Upper Cedar River Watershed in the U.S. Pacific Northwest. Results showed that the proposed model provides an acceptable representation of flow at the outlet of the study catchment. Model efficiencies and percent bias for the calibration period and the validation period were NSE = 0.55 and 0.65, and PBIAS = -2.8% and 2.1%, respectively. The WEPP-CMT provides a suitable foundation for the transport of reactive solutes (e.g. nitrates) at basin scales.</p><p><br></p>

<p>Current watershed-scale, nonpoint source (NPS) pollution models do not represent the processes and impacts of agricultural best management practices (BMP) on water quality with sufficient detail. To begin addressing this gap, a novel process-based, watershed-scale, water quality model (WEPP-WQ) was developed based on the Water Erosion Prediction Project (WEPP) and the Soil and Water Assessment Tool (SWAT) models. The proposed model was validated at both hillslope and watershed scales for runoff, sediment, and both soluble and particulate forms of nitrogen and phosphorus. WEPP-WQ is now one of only two models which simulates BMP impacts on water quality in ‘high’ detail, and it is the only one not based on USLE sediment predictions. Model validations indicated that particulate nutrient predictions were better than soluble nutrient predictions for both nitrogen and phosphorus. Predictions of uniform conditions outperformed nonuniform conditions, and calibrated model simulations performed better than uncalibrated model simulations. Applications of these kinds of models in real-world, historical simulations are often limited by a lack of field-scale agricultural management inputs. Therefore, a prototype tool was developed to derive management inputs for hydrologic models from remotely sensed imagery at field-scale resolution. At present, only predictions of crop, cover crop, and tillage practice inference are supported and were validated at annual and average annual time intervals based on data availability for the various management endpoints. Extraction model training and validation were substantially limited by relatively small field areas in the observed management dataset. Both of these efforts contribute to computational modeling research and applications pertaining to agricultural systems and their impacts on the environment.</p>