The aim of this thesis is to evaluate water quality and runoff characteristics in the Jenínský stream catchment. For this purpose analysis and data processing was performed. Two subcatchments, called J1 and J2, were monitored at this catchment area. Period of interest involves years 2008-2012. Results were compared with the period 1983-1985 when most of the land was used as arable land. The decrease in the concentrations of all evaluated indicators was caused by grassing and reduction in the use of fertilisers. Ranges of the values of selected indicators also decreased distinctly and their concentrations are stabilized. The greatest decrease of 79% (J1) and 87% (J2) was found in average ammonium concentrations. A beneficial effect of land use change to extensive agricultural management on water quality was proven.

This work deals with the revitalization of the Jenínský stream, the revitalization is mainly focused on the separation of pipes from some parts of the stream. The new track of the stream including a vegetation is proposed at its spring. The revitalization also concerns the drainage system, where a new drainage trail and a retention tank are proposed. For the appropriate design of the flow capacity, drainage of water from the river catchment was calculated and the flow and concentration of the substances in the stream were analyzed. Water, its composition and hydrological cycle are generally described in the literary research. It also explains the collision-draining process and the factors that affect it. Theoretic part deals with the revitalization of watercourses and, lastly, drainage systems are described.

Made available in DSpace on 2016-06-02T20:00:36Z (GMT). No. of bitstreams: 1 3409.pdf: 2199737 bytes, checksum: 5aff5a67e09c1c1d2a25bf26142c6ea9 (MD5) Previous issue date: 2010-08-23 / Financiadora de Estudos e Projetos / This study aimed to investigate the performance of an experimental rainwater treatment system for non-potable uses without the first-flush discharge, thus intending to control the quality of captured rainwater and to minimize the rainwater by-pass caused by the first-flush strategy. A full-scale direct filtration unit was operated and a solution of natural corn starch was used as the primary coagulant. The color, turbidity e coliform efficiencies of the unit was analyzed based on filtration loads and the net water production was estimated. The results indicated that the system was able to reduce the discharge of the first rain batch, although it was not fully adequate in terms of removal efficiency, suggesting that more studies are needed. The reduction of volume was equivalent to 1.7 mm in absolute terms (or 85%). The apparent color and turbidity removal was around 30 and 54% average, respectively. Additionally, the rainwater production cost for harvesting was R$ 0,99/m3 (or 90%) cheaper than the drinking water public source. / O presente trabalho objetivou investigar o desempenho de um sistema experimental de tratamento de água pluvial visando uso não potável, prescindindo o descarte da primeira chuva na expectativa de controlar a qualidade da água pluvial captada e minimizar o volume descartado. Para tal, utilizou-se uma estação de captação e tratamento de águas pluviais após passagem por telhado construída em escala real. Foram realizados ensaios de filtração direta com emprego de filtro de pressão e aplicação de solução de amido natural de milho como coagulante primário. Para avaliação do desempenho do sistema, foram analisadas a eficiência na remoção de impurezas ao longo das carreiras de filtração e a produção efetiva do sistema. Os resultados obtidos indicaram que com o emprego do sistema foi possível reduzir o descarte da primeira chuva, embora não tenha adequado plenamente as precipitações estudadas ao padrão de qualidade preconizado pela NBR 15527/07, sugerindo a necessidade da continuidade dos trabalhos. O tratamento investigado possibilitou redução no valor de descarte da primeira chuva equivalente a 1,7 L (ou 85%) por metro quadrado de área de captação. Em termos de residuais de cor aparente e turbidez, as reduções médias obtidas foram de 30 e 54%, respectivamente. Adicionalmente, comparando-se o custo de operação do sistema de tratamento empregado com a tarifa de água tratada cobrada pela concessionária local, obteve-se uma economia equivalente a, aproximadamente, R$ 0,99/m3 (ou 90%). Por fim, foram discutidas alternativas para melhoria do sistema experimental investigado.

The role of streams in the global carbon budget was for a long time neglected, since they were considered passive transporters of carbon from land to sea. However, studies have shown that streams are often supersaturated in carbon dioxide (CO2), making them sources of carbon to the atmosphere. The main sources of stream CO2 are in-stream mineralization of organic matter and transport of carbon from the catchment. The catchment derived CO2 could both be of biogenic (respiration) or geogenic (weathering) origin. Most studies regarding the topic rely on measurements carried out in forest-dominated catchments, while agricultural streams are under-represented. The objective of this study was to examine partial pressure of CO2 (pCO2) in streams in catchments dominated by agriculture. This was done to increase the knowledge about agricultural influence on stream pCO2, and to provide a basis for planning mitigation strategies for reducing CO2 emissions from the agriculture sector. Sampling was performed in ten streams draining agriculture-dominated catchments around Uppsala, Sweden, from June to November 2017. Measurements of pCO2 were carried out with floating chambers, equipped with CO2 sensors. Nutrients, organic carbon, discharge and different chemical variables were also measured. For correlation tests, the method Kendall’s Tau was used. Catchments were delineated in a geographic information system (GIS) and the CORINE Land Cover dataset was used to examine land use. Stream specific median pCO2 varied from 3000 to 10 000 μatm. In some streams, pCO2 exceeded 10 000 μatm, which was outside of the sensor’s measurement range. Values of pCO2 were high compared to similar studies in forested catchments, which could indicate that occurrence of agriculture in the catchment increases stream CO2. Correlation was found between pCO2 and discharge, with negative correlation in five streams and positive correlation in two. Negative correlation was found between pCO2 and pH and percentage of dissolved oxygen, respectively. No significant correlation was found between pCO2 and fraction of agricultural land use, nutrients or organic carbon. Further studies are needed to examine the sources of CO2, since it is possible that a large part of the CO2 has a geogenic origin. The floating chamber method should be revised to reduce the sensor’s sensitivity to condensation and cold temperatures, and to increase the measuring range.

The aim of the thesis is localization and interpretation of paths of concentration runoff in digital terrain model. Digital terrain model(DTM) is processed for the catchment of the Jenín stream, where The Faculty of Agriculture has held the research since the year 2004. For creation of DTM following software programs were used for comparison: Erdas and ArcGIS. Digitalized maps of contour lines for this catchment were the backgrounds for creation of the DTM. Localization of paths of concentration runoff and natural thalwegs was made on created DTM. Then was the comparison of models and the real topography of the catchment realized. Possible reasons of differences were discussed in discussion. Different (in colours and resolution) variations of DTM with localized paths of concentration runoff are the result, with the view of better legibility and more truly representation of real topography of the landscape.

The goal of this thesis is to evaluate erosion processes and runoff conditions in a part of catchment Zubčický potok containing the land arrangement Věžovatá Pláně. I drew up the area description for this catchment in terms of geomorfological, geological, pedological, climatic and phytogeographical aspect. For the evaluation of erosion processes in the solved area was used the universal soil loss equation by Wischmeier and Smith and in the microcatchment was used the CN method. Further, flow conditions was evaluated using Čerkašin equation. The result of this thesis is evaluation of erosion and runoff conditions, concept of erosion control measures and evaluation their impact on erosion and runoff conditions in the microcatchment.

This thesis creates a part of more extensive scientific study, which evaluates effects of different agricultural management on ecological functions and on landscapes´s water regime in source water areas of Bohemian Forest. A one of examined characteristic of catchment is biodiversity of plant and animal communities. The aim of my thesis is a comparsion of diversity of small terrestrial mammals in three catchments with similar nature conditions, but different management. Small terrestrial mammals is a group of vertebrates often used for study of enviromental state, because of their high reprodctive potential, good invasive ability and ability to indicate the changes in environmental quality. The master thesis is a follow-up to a previous bachelor thesis and extends it significantly. A teoretical part involves literary review of small mammals´s occurrence in Bohemian Forest, their micro-habitat preferences and the effect of management on the biodiversity of their communities. Practical part of the thesis contains evaluation of the results of capture-mark-release trapping, which took place from June to September of the years 2007 and 2009. In those two years 52 individuals were captured. From this amount, 7 individuals were captured twice. Captured small mammals were included into 5 species, whose occurrence in studied localities was expected. There were yellow-necked mouse (Apodemus flavicollis - 22 individuals), field vole (Microtus agrestis - 6 individuals), common vole (Mircotus arvalis - 10 individuals), bank vole (Clethrionomys glareolus {--} 2 individuals) and common shrew (Sorex araneus - 5 individuals). In the Bukový potok catchment 20 individuals were captured in 2007 and only 2 individuals in 2009. They belong to species: Apodemus flavicollis, Clethrionomys glareolus and Sorex araneus. In catchment of Mlýnský potok no individual was captured in 2007 and 10 individuals of only one species (Mircotus arvalis) were captured in 2009. In Horský potok catchment 5 individuals were captured in 2007 and 8 individuals in 2009. Three species were found: Apodemus flavicollis, Microtus agrestis, Clethrionomys glareolus a Sorex araneus. The largest positive change of abundance between 2007 and 2009 was found in the Mlýnský potok catchment. The largest fall of abundanace was in the catchment of Bukový potok. Only in catchment of Horský potok the relatively stable abundance was noticed. The thesis was supported by projects: MSM 6007665806, NAZV-QH82106 a NPV2-2B08006.

Mercury (Hg) which originates from global emissions to the atmosphere can deposit far away from the source. There is often a weak correlation between Hg deposition and concentrations in runoff, therefore catchment specific parameters might be of importance in controlling the amount of Hg ending up in watercourses and fish. Total mercury (THg) and methylmercury (MeHg) concentrations in watercourses are correlated to organic matter (OM), and in this study total organic carbon (TOC) is used as a proxy for OM. This study covers data from 125 watercourses in Sweden, and investigates the impact of e.g. Topographic Wetness Index (TWI), forest type, soil and bedrock types, deforestation and catchment size on the THg and MeHg concentrations as well as on the residuals from the regression between THg and TOC. Previous studies have found strong correlations between THg and OM as well as MeHg and OM but few previous studies have studied influences of catchment specific factors on THg and MeHg runoff concentrations with data of this large spatial and temporal scale. The catchment characteristics were extracted through ArcMap and projection to latent structures (PLS) models were created to evaluate what characteristics had the strongest influence on the variation in THg and MeHg concentrations as well as on the THg/TOC residuals. A strong correlation was found between THg and TOC, but a weaker one between MeHg and TOC. The MeHg concentrations were found to be dependent on variables which co-vary with TOC, as well as on latitude. The negative impact of latitude on MeHg concentrations could be due to methylation being temperature dependent or reflecting a spatial variation in Hg deposition from north to south of Sweden. Amount of deforestation was found to have an impact on the THg concentrations, indicating that deforestation leads to larger THg fluxes from soil to stream. The fact that variables measuring OM content in the streams were strongly influencing THg and MeHg concentrations, and the fact that few catchment characteristics were of importance, indicate the high importance of OM in explaining THg and MeHg also at this large spatial and temporal scale. / Studien sammanfattar hur halter av kvicksilver, och dess relation till organiskt material, i vattendrag påverkas av olika landskapsvariabler. Få tidigare studier har studerat hur kvicksilverhalten i vattendrag varierar beroende på avrinningsområdets karaktär i så stor skala, vad gäller antal områden och antal mätvärden, som i denna studie. Kvicksilver (Hg) är ett skadligt ämne för människor och natur, eftersom det i sin biotillgängliga form, metylkvicksilver (MeHg), är ett nervgift som kan orsaka stor skada på centrala nervsystemet. I de flesta vattendrag i Sverige är den uppmätta kvicksilverhalten i fisk högre än världshälsoorganisationens rekommenderade gränsvärden för fisk som föda. Kvicksilver härstammar från globala utsläpp till atmosfären som kan falla ned långt ifrån utsläppskällan. Då det ofta inte finns något rakt samband mellan kvicksilvernedfallet och de koncentrationer som återfinns i avrinnande vatten så kan områdesfaktorer och aktiviteter i de lokala avrinningsområdena ha stor betydelse för hur mycket kvicksilver som hamnar i våra ytvatten och sedan i fisken. Ett starkt samband har påvisats mellan mängden organiskt material i vattendrag och koncentrationen av totalkvicksilver (THg). I denna studie testas om sambandet mellan kvicksilver och organiskt material, mätt som total organiskt kol (TOC), kvarstår över lång tid (upp till 17 år) och hög rumslig upplösning (125 avrinningsområden). Eftersom ett relativt starkt samband återfanns fokuserade den här studien på att vidare utreda hur sambandet mellan THg och TOC, samt koncentrationer av MeHg, påverkas av områdesfaktorer i de olika avrinningsområdena. Det undersöktes hur skogstyp, jordarts- och bergartstyper, skogsavverkning, avrinningsområdets storlek samt Topographic Wetness Index (TWI, ett mått på hur topografi och markfuktighet är fördelat inom ett avrinningsområde), påverkar koncentrationer av total- och metylkvicksilver samt relationen mellan totalkvicksilver och organiskt material. Information om avrinningsområdena togs fram i GIS och statistiska modeller för hur områdesfaktorer påverkar kvicksilverkoncentrationer skapades genom PLS analyser (Projection to Latent Structures). Latitud visade sig ha en negativ påverkan på MeHg koncentrationerna; desto högre latitud desto mindre MeHg, vilket kan bero på att metylering är temperaturdriven process och/eller att reflektera en variation i Hg deposition från norra till södra Sverige. Studien kan sammanfattningsvis säga att inget samband hittades mellan de övriga landskaps-variablerna som undersökts i studien och kvicksilver koncentrationer.

A Mata Atlântica é o bioma mais ameaçado do Brasil. Sua degradação substancial ocorreu desde a chegada dos europeus ao país por meio da mudança de uso solo e pela exploração da floresta. No entanto, pouco se sabe a respeito das conseqüências hidrológicas e biogeoquímicas da mudança de uso do solo nos domínios do referido ecossistema. Neste contexto, as microbacias hidrográficas têm sido objeto de muitos estudos devido sua alta sensibilidade aos processos hidrológicos e biogeoquímicos ocorrentes dentro delas. No presente estudo, calculou-se o balanço hídrico anual de uma microbacia coberta por pastagem na região do litoral norte do Estado de São Paulo. Essa bacia originalmente era coberta por floresta ombrófila densa. Em adição, amostrou-se água do escoamento do riacho, escoamento superficial, solução do solo (30, 50 e 90 cm de profundidade), água subterrânea, e precipitação de 05/12/2007 à 04/12/2008 para a análise de nitrogênio inorgânico. O conteúdo de nitrogênio (N-NH4 + e N-NO3 -) foi determinado por análise por injeção em fluxo (FIA). Com o intuito de elucidar os processos hidrológicos que geram escoamento direto, mediu-se a condutividade hidráulica do solo em condição de saturação a 15, 30, 50 e 90 cm com um permeâmetro de carga constante. Como resultados, foi obtido que o sistema hidrográfico possui evapotranspiração, calculada para o período de estudo, de 697 mm (precipitação anual e deflúvio anual, respectivamente, de 1433 mm e 736 mm); por meio da curva de duração de fluxo, o escoamento de base foi inferida como a via hidrológica com maior contribuição ao deflúvio anual. O escoamento superficial é pouco expressivo devido ao fato que 77% dos eventos de chuva se enquadram na classe de intensidade de 0-5 mm h-1 que está abaixo da condutividade hidráulica do solo em condição de saturação a 15 cm de profundidade (22 mm h-1). O baixo coeficiente de escoamento superficial (0,01) obtido em parcelas corrobora essa assertiva. Ademais, como predominam chuvas de baixa intensidade, apesar de haver degradação física do solo, não espera-se diferenças expressivas na produção de escoamento direto. A maioria das amostras tiveram suas concentrações abaixo do limite de detecção (0,71 µM e 0,35 µM para N-NH4 + e N-NO3 - respectivamente). Na maioria dos compartimentos e processos hidrológicos o amônio predominou em relação ao nitrato. Para a solução do solo, percebe-se que há pulsos de nitrogênio inorgânico quando o solo se torna menos úmido. Nota-se pelo balanço de nitrogênio inorgânico associado à água que a microbacia possui um ganho líquido (0,95 kg N ha-1 ano-1) de nitrogênio já que o influxo foi equivalente a 1,10 kg N ha-1 ano-1 e o efluxo foi de 0,15 kg N ha-1 ano-1. Em relação aos estudos semelhantes conduzidos em florestas e pastagens, percebe-se que a pastagem é muito mais pobre que as florestas e ainda mais pobre do que muitas pastagens no tocante ao nitrogênio inorgânico o que provavelmente decorre do método de a mudança de uso do solo, da ausência de fertilização, da alta taxa de lotação e da idade da mesma. / The Atlantic forest is the most endangered biome of Brazil. Its significant destruction has taken place since the arrival of Europeans settlers in the country. These Europeans destructed most part of it by changing land use and also due to forest exploitation. In this way, very little information is known about the hydrological and biogeochemical consequences of land use change in the region of this once huge ecosystem. In this context, small catchments have being used to assess these cited consequences of land use change due to their high sensitivity of hydrological and biogeochemical process that occur within them. In the present study, the annual water budget of a small watershed covered by grass (pasture) located in the north coast of the Sao Paulo State, Brazil has been calculated. Additionally, (1) stream water, (2) surface runoff, (3) soil solution (at 30, 50 and 90 cm depth), (4) groundwater and (5) precipitation were sampled weekly and, afterwards, due to analytical reasons, (2) and (3) were sampled biweekly, to determine the concentration of inorganic nitrogen (N-NH4 + and N-NO3 -) by FIA. Moreover, aiming to clarify the possible hydrological process of stormflow, the soil saturated hydraulic conductivity was measured at various depths (15, 30, 50 and 90 cm). The results obtained are: the evapotranspiration of the watershed vegetation, calculated for the study period, was 697 mm (annual precipitation and annual water yield, respectively, de 1433 mm e 736 mm). By the flow duration curve, the baseflow was inferred as the main hydrological pathway that contributes to the total annual water yield. The surface runoff was not very expressive for the reason that 77% of rain intensity was sited in the class of 0 - 5 mm h-1 that is lower than the median of soil saturated hydraulic conductivity at 15 cm depth (22 mm h-1). The low runoff coefficient (0,01) calculated from the runoff plots assures this result. Although soil physical degradation is present, it is not expected an expressive increment of direct runoff generation for the reason that low intensity rainfall predominates and does not exceed Ksat at 15 cm. Little inorganic nitrogen is found in the hydrological processes and pools. The majority of the samples had their inorganic nitrogen concentration below detection limits (0,71 µM e 0,35 µM for N-NH4 + e N-NO3 - respectively). In most pools and hydrological pathways the ammonium predominates against nitrate. For soil solution, it is notable that more inorganic nitrogen was found when the soil gets less wet. The observation of inorganic nitrogen balance dissolved in the water of rain and streamflow exhibits a net gain (0,95 kg N ha-1 year-1) of inorganic nitrogen because the input was 1,10 kg N ha-1 year-1 and the output was 0,15 kg N ha-1 year-1. If the results of nitrogen in the pools are compared to other similar catchment studies with land uses of forest and also pasture in Brazil and elsewhere, it is possible to conclude that the pasture presented here is poorer than forests and even some pastures. This fact may be a consequence of the land use clearing method, the lack of fertilization, the high stocking rates and also due to the pasture age.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A deficiÃncia hÃdrica em regiÃes semiÃridas, como o Nordeste do Brasil, representa um dos principais fatores limitantes ao desenvolvimento econÃmico, com graves consequÃncias sociais. Para garantir a conservaÃÃo dos recursos hÃdricos disponÃveis, à imprescindÃvel o controle de aÃÃes antrÃpicas que impactem negativamente a disponibilidade hÃdrica. Por exemplo, a ocupaÃÃo desordenada do solo e a utilizaÃÃo de prÃticas inadequadas na agricultura intensificam a erosÃo e o transporte de sedimentos, interferindo diretamente na disponibilidade hÃdrica. O assoreamento de reservatÃrios causa a reduÃÃo de sua capacidade de armazenamento e, consequentemente, sua capacidade de regularizar vazÃes com elevada garantia. O aporte de sedimentos a mananciais contribui tambÃm para a degradaÃÃo da qualidade da Ãgua, atravÃs do aumento da turbidez, o que provoca a reduÃÃo da concentraÃÃo de oxigÃnio dissolvido, e do enriquecimento de nutrientes. Adicionalmente, a erosÃo do solo à um dos principais fatores de degradaÃÃo ambiental, provocando a perda de nutrientes das camadas superficiais de solo. Portanto, uma avaliaÃÃo precisa dos fluxos de sedimento ao longo de sua trajetÃria à imprescindÃvel para a identificaÃÃo de Ãreas potencialmente erosivas e de locais onde predominam processos de deposiÃÃo. Para isso, faz-se necessÃrio o conhecimento das condiÃÃes de transporte dos sedimentos atravÃs e entre os diferentes compartimentos da bacia hidrogrÃfica. O potencial de movimento de uma partÃcula no sistema, denominado de conectividade no transporte de sedimentos, destaca-se como fator determinante para a compreensÃo e estimativa dos fluxos de massa sÃlida. De forma a se avaliar o efeito da conectividade sobre a produÃÃo de sedimentos na regiÃo semiÃrida do Brasil, realizou-se simulaÃÃo hidrossedimentolÃgica da bacia hidrogrÃfica de meso-escala do aÃude BenguÃ, CearÃ, utilizando-se o modelo WASA-SED. Constatou-se que, de um modo geral, o balanÃo de Ãgua no solo determina as condiÃÃes de geraÃÃo de escoamento na regiÃo de estudo: muito embora haja uma predominÃncia de iniciaÃÃo do escoamento superficial por processo Hortoniano, na escala de bacia hidrogrÃfica o excesso de precipitaÃÃo à percebido somente em eventos de grande magnitude ou apÃs sequÃncias de eventos chuvosos, quando a conectividade hidrolÃgica à elevada. Assim, as condiÃÃes de transporte limitam a produÃÃo de sedimentos, gerando padrÃes espaciais muito semelhantes de escoamento superficial e de produÃÃo de sedimentos. Na escala de bacia hidrogrÃfica, o padrÃo espacial de conectividade mostrou-se fortemente relacionado a caracterÃsticas hidrÃulicas do solo, enquanto que na escala de vertente, caracterÃsticas topogrÃficas locais desempenharam um papel mais importante no transporte de sedimentos. A simulaÃÃo de caracterÃsticas especÃficas do semiÃrido pelo modelo WASA-SED, tais como escoamento do tipo Hortoniano, reinfiltraÃÃo a jusante, redistribuiÃÃo lateral de escoamento e densa rede de reservatÃrios, permitiu a estimativa satisfatÃria dos fluxos de Ãgua e sedimentos tanto na bacia do Benguà (933 kmÂ) como na sub-bacia de Aiuaba (12 kmÂ). Um teste mais rigoroso foi realizado com o uso da tÃcnica de CÃsio-137 como traÃador de erosÃo/deposiÃÃo de sedimentos. A comparaÃÃo entre valores modelados e medidos com 137Cs em uma vertente representativa demonstrou boa correlaÃÃo entre os valores. Apesar de se tratar de um resultado local, tal comparaÃÃo indica que o modelo WASA-SED simule os fluxos de sedimento de maneira satisfatÃria tambÃm na escala de vertente / Water deficit in semiarid regions, such as the Northeastern Brazil, is a major limiting factor to economic development, with serious social consequences. To ensure the conservation of the available water resources, it is essential to control the human activities that impact negatively on water availability. For instance, uncontrolled soil use and improper agricultural practices, tend to intensify erosion and sediment transport processes, with direct impacts on water availability. Reservoirs siltation causes a reduction of the storage capacity and, hence, of the ability to supply water with high reliability. Sediment input to water bodies also contributes to water quality degradation, by increasing turbidity, which results in a reduction of the concentration of dissolved oxygen, and nutrient enrichment. In addition, soil erosion is a major factor of environmental degradation, causing the loss of nutrients of the top soil layers. Therefore, an accurate assessment of sediment fluxes along its pathway is essential for the identification of potentially erosive areas and regions where deposition processes predominate. For such estimation, a good understanding of the conditions of sediment transport through and between the different catchment compartments is necessary. The potential for movement of the soil particles within the system, denominated connectivity in sediment transport, stands out as a determining factor for the understanding and estimation of the flow of solid mass. In order to evaluate the effect of connectivity on sediment yield in the semiarid region of Brazil, a hydrosedimentological simulation of the Benguà meso-scale catchment (CearÃ, Brazil) was carried out with the WASA-SED model. It was found that, in general, water balance in the soil matrix determinates the conditions for runoff generation in the study area: although there is a predominance of surface runoff initiation by Hortonian process, in the catchment scale, excess precipitation is observed only in events of great magnitude or sequences of rain events, when hydrological connectivity is high. Thus, the transport conditions limit sediment yield, generating very similar spatial patterns of runoff and sediment yield. At the catchment scale, the spatial pattern of connectivity was strongly related to soil hydraulic properties, while topographic characteristics played a more important role in sediment transport at the finer scale. The simulation of specific features of semiarid regions by the WASA-SED model, such as Hortonian-type flow, downstream re-infiltration of surface runoff, lateral flow redistribution and dense network of reservoirs, allowed a satisfactory estimate of both water and sediments fluxes in the Benguà catchment (933 km Â), as well as in the Aiuaba sub-basin (12 km Â). A more rigorous test was performed with the technique of Cesium-137 as a tracer of soil erosion/deposition. A comparison between modelled and measured (with 137Cs) values in a representative hillslope showed good correlation between the values. Even though it is a local result, this comparison indicates that the WASA-SED model must be able to simulate sediment fluxes satisfactorily also in the hillslope scale