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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Water and Carbon Balance Modeling: Methods of Uncertainty Analysis

Juston, John January 2010 (has links)
<p><em>How do additional data of the same and/or different type contribute to reducing model parameter and predictive uncertainties?</em> This was the question addressed with two models – the HBV hydrological water balance model and the ICBM soil carbon balance model – that were used to investigate the usefulness of the Generalized Likelihood Uncertainty Estimation (GLUE) method for calibrations and uncertainty analyses.  The GLUE method is based on threshold screening of Monte Carlo simulations using so-called informal likelihood measures and subjective acceptance criterion. This method is highly appropriate for model calibrations when errors are dominated by epistemic rather than stochastic uncertainties.  The informative value of data for model calibrations was investigated with numerous calibrations aimed at conditioning posterior parameter distributions and boundaries on model predictions.  The key results demonstrated examples of: 1) redundant information in daily time series of hydrological data; 2) diminishing returns in the value of continued time series data collections of the same type; 3) the potential value of additional data of a different type; 4) a means to effectively incorporate fuzzy information in model calibrations; and 5) the robustness of estimated parameter uncertainty for portability of a soil carbon model between and tropical climate zones.  The key to obtaining these insights lied in the methods of uncertainty analysis used to produce them.  A paradigm for selecting between formal and informal likelihood measures in uncertainty analysis is presented and discussed for future use within a context of climate related environmental modeling.</p>
82

Irrigation with wastewater in Andhra Pradesh, India, a water balance evaluation along Peerzadiguda canal / Bevattning med avloppsvatten i AndhraPradesh, Indien, en vattenbalansutvärdering längs Peerzadiguda kanal

Hytteborn, Julia January 2005 (has links)
<p>Studien behandlar bevattningsgivornas storlek av avloppsvatten längs Peerzadiguda bevattningskanal i Andhra Pradesh, Indien. Peerzadiguda bevattningskanal är belägen norr om Musifloden nedströms Hyderabad som är huvudstad i delstaten Andhra Pradesh i Indien.</p><p>I regioner med knappa vattenresurser kan avloppsvatten vara en värdefull resurs i jordbruk som kräver bevattning. Så är fallet längs Musifloden som innehåller Hyderabads orenade och delvis renade avloppsvatten. Studieområdet är den del av marken runt Peerzadiguda bevattningskanal som är bevattnad av densamma. Flödet i kanalen mättes, vattenförlusterna uppskattades och bevattningen över hela området beräknades. I ett geografiskt informationssystem (GIS) beräknades arean på studieområdet och några kartor tillverkades. För några fält i området beräknades också den aktuella bevattningen med mätningar av flödet i bevattningskanalerna på fälten och med hjälp av intervjuer med lantbrukarna. Bevattningen av fälten utfördes med bassängbevattning. Den aktuella bevattningen användes i vattenbalansberäkningar för rotzonen för de grödor som växte i området: grönsaker, fodergräs och ris. En optimal bevattning beräknades.</p><p>Bevattningen över hela studieområdet beräknades till 41 mm per dag. Den aktuella bevattningen som uppmättes på fälten var mindre men de utförda vattenbalansberäkningarna visade att vattenförluster förekom, i vissa fall stora sådana. När den optimal bevattning användes i beräkningarna minskade förlusterna. Stora vattengivor och användningen av bassänbevattning och leder till vattenförluster och att stora mängder patogener tillförs jorden.</p> / <p>This thesis focuses on the amounts of wastewater irrigating the land along Peerzadiguda irrigation canal in Andhra Pradesh, India. The Peerzadiguda irrigation canal is located north of Musi river downstream Hyderabad, the capital of the Indian state Andhra Pradesh.</p><p>In regions where the freshwater resources are scarce, wastewater can become a valuable resource in irrigated agriculture. This is the case along Musi river that contains Hyderabad’s untreated and partly treated wastewater. The study area is the land around Peerzadiguda irrigation canal that is irrigated with water from the canal. The flow in the irrigation canal was measured, water losses were estimated and the irrigation amount over the whole study area was quantified. In a Geographical Information System (GIS) the size of the study area was measured and a few maps produced. The actual irrigation on a few farms was also calculated from measurements of the irrigation canals on the farms and from data from interviews with the farmers. The irrigation of the fields was preformed with basin irrigation. The values of the actual irrigation was used in water balance calculations of the root zone for the crops growing in the area: vegetable, paragrass and paddy rice. An optimal irrigation scheme was then calculated.</p><p>The irrigation over the whole study area was calculated to 41 mm per day. The actual irrigation measured on the fields was lower but the water balance calculations showed that the irrigation leads to water losses, in some cases large losses. With the optimal irrigation amount used in the water balance the water losses were reduced. The use of basin irrigation and the large amount of irrigation water leads to water losses and larger amounts of pathogenic organisms is added to the soil.</p>
83

The role of crack willow in the wetland water balance, Moutere region, New Zealand

Amaravathi, Kiran Kumar January 2010 (has links)
The Waiwhero wetland (16 ha) is one of the largest wetlands in the Rosedale Hills, 35 km north-west of Nelson, New Zealand. It has an extensive cover of Salix fragilis L. (crack willow) and has been hypothesised to be a source of groundwater recharge for the Moutere aquifers, an important local groundwater system. However the wetland could also be a groundwater discharge zone, because of the geological boundary that it straddles. The overall aim of this study was to determine the direction of groundwater flux of the wetland by measuring the water balance, with particular emphasis on the transpiration rates from the crack willow trees. The average daily transpiration (measurement was for 230 days) of crack willows in the wetland (6.4 mm/day) was close to twice the potential evapotranspiration (PET) for grassland (3.9 mm/day). The highest measured willow transpiration rate was 12.4 mm/day and the lowest was 0.8 mm/day. High transpiration from crack willows was due to the horizontal energy fluxes (advective energy), tree physiological characters and high soil water content. The study established that the wetland is a groundwater discharge zone with, on average for the two summer periods (2008 and 2009), the net groundwater discharge being 4.8 mm/day. The daily water balance results between two major rainfall events showed that the initial discharge source was from the surrounding hills and later stabilized at around 6 to 14 mm/day. It was believed to be a contribution from the shallow and deep aquifers or a combination of local region inflow and aquifers. The water balance showed that the main loss of water through the hydrological system of the wetland during summer was from the high transpiration of willows (7.7 mm/day). The extent of water savings estimated for the 16 ha wetland through a hypothetical situation of willow removal, and the assumption that it is filled with open water without any canopy cover, was 688 m3/day. However this water savings rate if applied to a large area of crack willow stands would be quite high. On similar lines it is important to understand the transpiration rates of other wetland tree species in New Zealand. This information would help in preparing regional council plans for the introduction of tree species in the wetland for better management of the water resources and sustainable ecosystem management.
84

CONTINENTAL SCALE DIAGNOSTIC EVALUATION OF MONTHLY WATER BALANCE MODELS FOR THE UNITED STATES

Martinez Baquero, Guillermo Felipe January 2010 (has links)
Water balance models are important for the characterization of hydrologic systems, to help understand regional scale dynamics, and to identify hydro-climatic trends and systematic biases in data. Because existing models have, to-date, only been tested on data sets of limited spatial representativeness and extent, it has not yet been established that they are capable of reproducing the range of dynamics observed in nature. This dissertation develops systematic strategies to guide selection of water balance models, establish data requirements, estimate parameters, and evaluate performance. Through a series of three papers, these challenges are investigated in the context of monthly water balance modeling across the conterminous United States. The first paper reports on an initial diagnostic iteration to evaluate relevant components of model error, and to examine details of its spatial variability. We find that to conduct a robust model evaluation it is not sufficient to rely upon conventional NSE and/or r^2aggregate statistics of performance; to have reasonable confidence that the model can provide hydrologically consistent simulations, it is also necessary to examine measures of water balance and hydrologic variability. The second paper builds upon the results of the first, and evaluates the suitability of several candidate model structures, focusing specifically snow-free catchments. A diagnostic Maximum-Likelihood model evaluation procedure is developed to incorporate the notion of `Hydrological Consistency' and controls for structural complexity. The results confirm that the evaluation of hydrologic consistency, based on benchmark comparisons and on stringent analysis of residuals, provides a robust basis for guiding model selection. The results reveal strong spatial persistence of certain model structures that needs to be understood in future studies. The third paper focuses on understanding and improving the procedure for constraining model parameters to provide hydrologically consistent results. In particular, it develops a penalty-function based modification of the Mean Squared Error estimation to help ensure proper reproduction of system behaviors by minimizing interaction of error components and by facilitating inclusion of relevant information. The analysis and results provide insight into the identifiability of model parameters, and further our understanding of how performance criteria should be applied during model identification.
85

Modelling of the water balance and nutrient dynamics of Mhlanga Estuary.

19 January 2011 (has links)
Waste water discharge into a temporary open/closed estuary (TOCE) system introduces two main concerns namely (1) the effects on the water balance of the system (quantity) and (2) the effects on the nutrient dynamics (water quality). Changes to mouth breaching patterns can severely impact the hydrological and ecological functioning of TOCEs, while excessive nutrient loading can lead to eutrophic conditions and algal blooms. Algal blooms occur when residence times during closed mouth conditions exceed the time scale for growth of the microalgal community. The aim of this study was to formulate a model in order to predict eutrophication events using the Mhlanga Estuary as a case study. The Mhlanga Estuary is situated approximately 19 km northeast of Durban and has a small catchment «100km2 ). The Phoenix and Mhlanga waste water treatment works (WWTW) collectively discharge approximately 20MI of treated effluent into the Mhlanga River per day. A simple daily-time-step water balance model was selected to model the hydrodynamics of the system. The model included various inputs and outputs of the system, residence time, storage, breaching water levels and time for mouth closure to occur. The result of the water balance model was a daily prediction of the mouth state and volume, and an indication of the breaching frequency. Observed mouth state data and measured water levels were used to test the model. In order to predict eutrophication events and trends at the Mhlanga Estuary, it was required that the conditions at which this would occur be investigated. This included the collection of samples (physico-chemical and chlorophyll-a) on a weekly basis for three months, a period that included three breaching events. Due to the complexity required in developing a nutrient dynamics model, a simpler approach was selected. The grey water index (GWI) was formulated in order to account for nutrient loadings into the estuary. WWTW discharge data were provided by eThekwini Municipality Water and Sanitation (EMWS). Initial results showed that under ideal conditions, an algal bloom would occur approximately fourteen days following re-closure of the Mhlanga mouth. The eutrophication index (E j ) was then formulated to account for both residence time and nutrient concentrations. The Ej at which eutrophic conditions can be expected was found to be about 50 %. It is important to note that this value for Ej is expected to be site specific and only accounts for the Mhlanga Estuary, but the concept can be generalized to other similar estuaries. Water levels simulated using the water balance model and observed mouth state data produced similar levels to those measured by DWAF. Following simulations of different flow scenarios (75% and 150% increase in WWTW discharges), it was found that an increase in capping flows resulted in more frequent breaching events and longer open mouth conditions. The risk of eutrophic conditions also increased with an increase in WWTW capping flows. Algal blooms are predicted to continue despite more frequent breaching events induced by an increase in capping flows. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2007.
86

Comparing Three Approaches of Evapotranspiration Estimation in Mixed Urban Vegetation: Field-Based, Remote Sensing-Based and Observational-Based Methods

Nouri, Hamideh, Glenn, Edward, Beecham, Simon, Chavoshi Boroujeni, Sattar, Sutton, Paul, Alaghmand, Sina, Noori, Behnaz, Nagler, Pamela 10 June 2016 (has links)
Despite being the driest inhabited continent, Australia has one of the highest per capita water consumptions in the world. In addition, instead of having fit-for-purpose water supplies (using different qualities of water for different applications), highly treated drinking water is used for nearly all of Australia's urban water supply needs, including landscape irrigation. The water requirement of urban landscapes, particularly urban parklands, is of growing concern. The estimation of evapotranspiration (ET) and subsequently plant water requirements in urban vegetation needs to consider the heterogeneity of plants, soils, water, and climate characteristics. This research contributes to a broader effort to establish sustainable irrigation practices within the Adelaide Parklands in Adelaide, South Australia. In this paper, two practical ET estimation approaches are compared to a detailed Soil Water Balance (SWB) analysis over a one year period. One approach is the Water Use Classification of Landscape Plants (WUCOLS) method, which is based on expert opinion on the water needs of different classes of landscape plants. The other is a remote sensing approach based on the Enhanced Vegetation Index (EVI) from Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on the Terra satellite. Both methods require knowledge of reference ET calculated from meteorological data. The SWB determined that plants consumed 1084 mmyr(-1) of water in ET with an additional 16% lost to drainage past the root zone, an amount sufficient to keep salts from accumulating in the root zone. ET by MODIS EVI was 1088 mmyr(-1), very close to the SWB estimate, while WUCOLS estimated the total water requirement at only 802 mmyr(-1), 26% lower than the SWB estimate and 37% lower than the amount actually added including the drainage fraction. Individual monthly ET by MODIS was not accurate, but these errors were cancelled out to give good agreement on an annual time step. We conclude that the MODIS EVI method can provide accurate estimates of urban water requirements in mixed landscapes large enough to be sampled by MODIS imagery with 250-m resolution such as parklands and golf courses.
87

Vliv srážek na mělké jímání minerálních vod / The influence of precipitation on shallow mineral water abstraction

Hlaváčová, Michaela January 2014 (has links)
This study focuses on the influence of precipitation on shallow catchments of mineral springs in the special area of Františkovy Lázně. The thesis was made on the basis of the data provided by the company Spa Františkovy Lázně a.s.. The interdependent relations between yield springs, precipitations, atmospheric pressure and the content of free CO2 were studied. These relations were observed onto six springs - František, Luční, Nový, Solný, Železnatý and Žofie. The precipitations were compared with the yield of individual springs. The season was proved by three springs (František, Železnatý and Žofie). Retention of the precipitation was determined for springs František, Solný, Železnatý and Žofie. Considering more than half a year delay, we cannot claim that the precipitations should have a major influence on the dotation of mineral springs. The downtrend was founded for the free CO2 in all researched resources. Significant indirect relation was found using the correlation coefficient between atmospheric pressure and free CO2.
88

Spatiotemporal streamflow variability in a boreal landscape : Importance of landscape composition for catchment hydrological functioning / Avrinningens rumsliga och tidsmässiga variation i ett borealt landskap : Landskapets betydelse för avrinningsområdets hydrologiska funktion

Karlsen, Reinert Huseby January 2016 (has links)
The understanding of how different parts of a landscape contribute to streamflow by storing and releasing water has long been a central issue in hydrology. Knowledge about what controls streamflow dynamics across landscapes can further our understanding of how catchments store and release water, facilitate predictions for ungauged catchments, and improve the management of water quality and resources. This thesis makes use of data from the Krycklan catchment in northern Sweden. Streamflow data from 14 catchments (0.12 - 68 km2) with variable landscape characteristics such as topography, vegetation, wetland cover, glacial till soils and deeper sediment soils were used to investigate spatial patterns and controls on runoff. The differences in specific discharge (discharge per unit catchment area) between nearby catchments were large at the annual scale, and have the same magnitude as predicted effects of a century of climate change or the observed effects of major forestry operations. This variability is important to consider when studying the effects of climate change and land use changes on streamflow, as well as for our understanding of geochemical mass balances. Streamflow from different catchments was strongly related to landscape characteristics. The distribution of wetland areas had a particularly strong influence, with an annual specific discharge 40-80% higher than catchments with high tree volume on till soils. During drier periods, catchments with deeper sediment soils at the lower elevations of Krycklan had a higher base flow compared to both forested till and wetland catchments. This pattern was reversed at high flows. The storages releasing water to streams in downstream sediment areas were able to maintain base flow for longer periods and were less influenced by evapotranspiration compared to the more superficial till and wetland systems. The results of this thesis have led to a better understanding of the landscape wide patterns of streamflow during different seasons and time scales. The strong associations to landscape characteristics and variable spatial patterns with season and antecedent conditions form the basis for a conceptual understanding of the processes and spatial patterns that shape the heterogeneity of streamflow responses in boreal catchments. / Hur olika delar av landskapet påverkar vattenbalansen och bidrar till avrinning har länge varit en central fråga inom hydrologin. Kunskap om vad som styr avrinningsdynamiken i ett landskap kan öka vår förståelse av hur olika delar av landskapet bidrar till avrinning, hur avrinningsområden lagrar vatten och bildar avrinning, underlätta prognoser för avrinningsområden utan vattenföringsmätningar och förbättra hanteringen av vattenkvaliteten och vattenresurser. Denna avhandling använder data från Krycklans avrinningsområde i norra Sverige. Vattenföringsdata från 14 delavrinningsområden (0.12 - 68 km2) med olika landskapskarakteristik såsom topografi, vegetation och jordarter, användes för att undersöka rumsliga mönster hos avrinningen över olika tidsperioder samt hur landskapet påverkar variabiliteten. Skillnaderna i specifik avrinning (avrinning per areaenhet) mellan närliggande avrinningsområden var stor för årliga värden, och är i samma storleksordning som effekterna av stora skogsavverkningar samt av förutspådda effekter av det kommande seklets förväntade klimatförändringar. Denna variation är viktig att ta hänsyn till när man studerar hur klimatförändringar och ändrad markanvändning påverkar avrinningen, liksom för vår förståelse av geokemiska massbalanser. Avrinning från olika områden var starkt relaterad till deras landskapsegenskaper. Förekomsten av våtmarker hade ett särskilt starkt inflytande. Områden med en stor andel våtmarker hade 40-80% högre årlig specifik avrinning än områden med hög trädvolym på moränjordar. Under torrare perioder hade områden med djupare sedimentjordar hög avrinning jämfört med både områden med skog på morän och med våtmarker. Under höga flöden var detta mönster omvänt. De vattenlager som bidrar till avrinning i sedimentområden kan upprätthålla basflöde under längre tidsperioder och påverkas mindre av evapotranspirationen än de ytligare flödessystemen i morän och våtmarker. Avhandlingen har givit en bättre förståelse av avrinningens rumsliga variation under olika årstider och i olika tidsskalor. Det starka sambandet mellan landskapskarakteristik och avrinningens varierande mönster under olika årstider och lagringsförhållanden utgör en grund för en begreppsmässig förståelse av de processer och rumsliga mönster som skapar heterogeniteten i flödesrespons i boreala områden.
89

Classificação climática segundo Köppen e Thornthwaite e caracterização edafoclimática referente à região de Santa Maria, RS / Climatic classification by Köppen and Thornthwaite and edaphoclimatic characterization related to Santa Maria region, State of Rio Grande do Sul, Brazil

Fabres, Tanira Marinho 15 May 2009 (has links)
O presente trabalho foi desenvolvido com objetivo de analisar a classificação climática segundo Köppen e Thornthwaite (comparando os valores de armazenamento de água no solo, evapotranspiração real, deficiência hídrica e excedente hídrico para realização do balanço hídrico cíclico mensal), e de propor uma caracterização edafoclimática referente à região mesoclimática de Santa Maria, RS utilizando uma série histórica de 35 anos (de 1969 a 2003). De acordo com os resultados, as seguintes conclusões podem ser apresentadas: (a) a classificação climática segundo Thornthwaite ou Köppen pode ser feita com base na classe mais freqüente ou utilizando os valores médios de temperatura e de chuva e a capacidade de água disponível de 50 mm; (b) classificação climática segundo Thornthwaite: A r B\'3 a\' (classe mais freqüente) ou B4 r B\'3 a\' (utilizando os valores médios de temperatura e de chuva); (c) classificação climática segundo Köppen: Cfga (classe mais freqüente) ou Cwga (utilizando os valores médios de temperatura e de chuva); e (d) A29/42S,53/42W,95,35,11,7,27,2,20,3,5,5,471,1/5,1235,2672,1802,20,953,887,915,50: caracterização edafoclimática proposta. Isso significa que a evapotranspiração real é pelo menos 90% da evapotranspiração potencial de referência (classe A de disponibilidade hídrica), a localização geográfica é de 29o42\' (latitude sul), 53o42\' (longitude oeste) e altitude de 95 m, e que a série histórica apresenta 35 anos, sendo as temperaturas mínima e máxima mensal de 11oC (julho) e 27oC (fevereiro), a temperatura média anual de 20oC, respectivamente, com coeficiente de variação de 3%, e as chuvas mínima e máxima mensal de 5 mm (maio) e 471 mm (janeiro/maio), as chuvas mínima, máxima e média anual de 1235 mm, 2672 mm e 1802 mm, respectivamente, com coeficiente de variação de 20%, valores médios anuais de evapotranspiração potencial de referência, evapotranspiração real e excedente hídrico de 953 mm, 887 mm e 915 mm, respectivamente, adotando uma capacidade de água disponível de 50 mm. / The present work was developed with the purpose of analyzing the climatic classification by Köppen and Thornthwaite (comparing the values of soil water holding, actual evapotranspiration, water deficit and water excess for cyclic water balance using monthly data), and of proposing an edaphoclimatic characterization related to the mesoclimatic region of Santa Maria, State of Rio Grande do Sul, Brazil, using a historical series of 35 years (from 1969 to 2003). According to the results, the following conclusions can be presented: (a) the climatic classification by Thornthwaite or Köppen can be done based on the modal class or using the mean values of air temperature and rainfall and the soil water holding capacity of 50 mm; (b) the climatic classification by Thornthwaite is A r B\'3 a\' (modal class) or B4 r B\'3 a\' (using the mean values of temperature and rainfall); (c) the climatic classification by Köppen is Cfga (modal class) or Cwga (using the mean values of temperature and rainfall); and (d) A29/42S,53/42W,95,35,11,7,27,2,20,3,5,5,471,1/5,1235,2672,1802,20,953,887,915,50 is the proposed edaphoclimatic characterization. It means the actual evapotranspiration is at least 90% of the potential evapotranspiration (class A of soil water availability), the geographic localization is 29o42\' South (latitude), 53o42\' West (longitude) and altitude of 95 m, using a historic series of 35 years, being monthly minimum and maximum air temperatures of 11oC (July) and 27oC (February), the annual mean air temperature of 20oC, with coefficient of variation of 3%, and the monthly minimum and maximum rainfall of 5 mm (May) and 471 mm (January/May), the annual minimum, maximum and mean rainfall of 1235 mm, 2672 mm and 1802 mm, respectively, with coefficient of variation of 20%, and the annual mean values of potential evapotranspiration, actual evapotranspiration and water excess of 953 mm, 887 mm and 915 mm, respectively, using a soil water holding capacity of 50 mm.
90

Simulação hidrológica de bacias amazônicas utilizando o modelo de Capacidade de Infiltração Variável (VIC) / Hydrologic simulation of Amazon basins using the Variable Infiltration Capacity model (VIC)

Victoria, Daniel de Castro 22 February 2010 (has links)
Com 6 milhões de km2, a bacia Amazônica é o maior sistema hidrográfico do mundo, com descarga estimada de 209.000 m3 s-1, e a maior extensão contínua de floresta tropical. Porém, esta região é alvo de constantes ameaças, seja das pressões por desmatamento, ou por alterações climáticas. Neste contexto, compreender o funcionamento do sistema é essencial, seja para auxiliar na tomada de decisões ou estudos de cenários futuros. Este trabalho teve como objetivo avaliar e adaptar o modelo hidrológico de grandes bacias Variable Infiltration Capacity Model (VIC v.4.0.5), para as condições tropicais. Foram utilizados dados de descarga, precipitação, temperatura e velocidade do vento, e informações sobre tipo de solo e cobertura vegetal, para simular o ciclo hidrológico em 6 grandes bacias situadas na Amazônia: Santo Antônio do Içá, Japurá, Juruá, Negro, Madeira e Purus. O modelo foi calibrado a partir das descargas mensais, de 1980 a 1990, e seu funcionamento foi verificado para o período de 1990 a 2006. Não foi possível simular o ciclo hidrológico para as bacias com grande contribuição dos Andes, Santo A. Içá e Japurá, uma vez que a estimativa de precipitação nestas regiões é subestimada. Nas outras bacias, o modelo foi capaz de simular corretamente as vazões dos rios, apesar de apresentar problemas na estimativa da evapotranspiração (ET). Foram constatados problemas na partição da ET em seus componentes, transpiração da vegetação e evaporação da água interceptada. Uma possível correção foi avaliada, resultando em uma distribuição mais correta da ET em seus componentes porém, tal modificação resultou em redução da ET média simulada. Uma nova versão do modelo (v.4.1) acaba de ser lançada. Dentre as melhorias, destacam-se modificações na maneira como a ET é calculada, que visa corrigir os problemas aqui relatados. No entanto, tal versão ainda não foi avaliada nas condições tropicais / The Amazon river basin is the largest fluvial system in the world, discharging 209,000 m3 s-1 to the ocean. It also sustains the largest continuous tropical forest system. However, the region is under constant pressure from deforestation and climate change. For such reasons, its crucial to understand how the hydrological cycle functions. Such tools can be used for evaluation of future scenarios and guide decision making. The Variable infiltration Capacity Model (VIC) was evaluated and adapted to tropical conditions. Temperature, precipitation, wind speed, soil type and land cover maps were used to simulate the hydrological cycle in 2 sub-basins inside the Amazon: Santo Antônio do Içá, Japurá, Juruá, Negro, Madeira e Purus, covering the period from 1980 to 2006. The simulation was not possible for basins with large drainage area located in the Andes (Santo A. Içá and Japurá), due to underestimation of the precipitation. For the other basins, simulated discharge agreed with observed records, even though evapotranspiration (ET) estimates showed some problems. The ET partitioning in its components, transpiration and canopy evaporation, showed severe discrepancies. A correction was applied to the model, fixing the partitioning problem but it resulted in reduction of estimate ET. A new version of the model (v.4.1) has just been released, with changes in the way ET is estimated. However, this new version has not yet been tested in the Amazon

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